The same thing is used for audio electronics. The ground often gets connected between different amplifiers which have their own ground. (called ground loop) since it is a loop you will get an induced hum. Braking the loop is easy but often not safe. The diodes are an elegant and safe way to solve the issue.
When applying current across your test set up, with polarity one way you were depositing a layer on the copper coin, effectively 'electro plating' the coin, with polarity reversed you are effectively removing a fine layer and 'electro brightening' the coin. (even with low current it would not take long for a measurable difference in thickness to be achieved) Galvanic deposition and corrosion are fascinating when you look at them in depth. I had to deal with galvanic corrosion when I worked with a marine engineering firm and got into electroplating while making parts for small engineering projects. (depositing protective layers on precision parts with various anodising processes) If you have a go at some basic electrolytic cleaning and electroplating with a variety of materials You will get a better feel for how nobility of metals makes a huge difference & galvanic corrosion will make way more sense :-) Galvanic corrosion also occurs between Carbon Fiber and various metals, this is why many carbon fiber products are made with a fiberglass 'separation layer' at fixing points. Titanium fixings should be used in preference to other metals such as steels or aluminium alloys as Ti is a closer match to the nobility of carbon which greatly reduces galvanic current flow and corrosion extending the working lifetime of the fixings and the carbon fiber. Experiment with some carbon fiber in a 'test tank' (also try different salts, acids and alkali solutions) and you will be pleasantly surprised at the results! :-) just be aware that you can produce a few rather iffy by-products while experimenting with electrolytic effects. fume extractor is a good plan. Take it steady & keep having fun!
Sacrificial anode is connected to the hull. When I was in the petroleum business, we used galvanic protection to protect the fuel piping in old fueling stations before everyone changed over to double-walled fiberglass piping.
At the top of home water heaters you'll probably see a large bolt head. If you remove that while it is turned off and the water inlet valve is closed you'll see a corroded zinc rod or chain connected to it. That is a sacrificial rod designed to keep your water heater from consuming itself internally. If that rod completely dissolves, your water heater will start corroding and eventually leak.
A really interesting video Clive, its a shame they dont broadcast videos of this nature on television instead of the carp they publicly dispense, it would educate a lot more people instead of vegitating them with things like coronation street and eastenders. Well done.
I'm addicted to this channel, and I'm not entirely sure why... I'm primarily concerned with software when it comes to computers. Must be what happens when you mix bears and electronics ;P
"So that's what's causing the Corro.......sion." said the electrical engi-bear. "why the long pause?" asked the customer. The engi-bear looks ashamed retracting his claws and says "I was just born this way."
Very interesting Clive, I worked for British Telecom for many years and it was the eternal struggle to keep water out of the cables, using compressed air or grease and millions every year on new joint designs and testing. But an interesting thing is that they used a negative battery to power the lines. For several reasons, but the main one being electrolytic corrosion of the wires, mostly copper but still lots of Ali. The negative battery was supposed to stop the cables dissolving with the constant leaks in current to earth. Putting the meter across the pr showed -50v It wasn’t unusual to open a joint and find the Ali had turned to mush or was so thin it just crumbled. The copper was slightly more robust but still could be covered in green mush which was nicely conducting the current away to earth and the broard band and with it.. the fibre optics are much more reliable and replacing the copper at an incredible rate. There are sections of cable ( actually thousands of miles in total ) with 0.5mm copper to .5 Ali to .63 copper and back to Ali again with each connection, via crimps, changing the resistance, bits where engineers had split 2 prs and used the good leg of each to make a single pr, but now each leg being wrapped around a faulty leg instead of each other, this then causing broardband drop out and overhearing issues. Of course the ‘engineers’ are anything but these days so have no understanding of what or why they’re doing what they’re doing.
It's crazy that I had to go back to a video from 2016 from someone who basically never talks about boats to find this information. I kinda wish there were people in the youtube boating space that talked about stuff this in depth.
I worked as a commercial diver retrieving lost items, taking insurance photos, scrubbing hulls, fixing steering gear, you name it. Not one boat had an earth connection. They were all cut by the crew.
Interesting. Normally I would think of galvanic isolation as making something electronically float with respect to another thing, so that no current can flow if you connect just one wire between any point of each end. Like transformers' secondary windings, which you can connect in series or parallel, like batteries. This diode trick, on the other hand, only prevents current flow when there's less than 1 volt of potential difference, so it's a very different thing. But I suppose the term "galvanic" isn't very strict, so it fits this concept as well.
It appears that I may have been using the term "galvanic isolation" incorrectly for 40 years. I also thought it meant to isolate the sides so there could be no current flow.
1:42 - "Here's a sea...which is a very large container of salt water..." That massive understatement made me laugh way more than is socially acceptable. :)
I'd heard of sacrificial anodes, but not this. Very interesting. I feel like playing with electroplating now. My other half's dad used to do electroplating. Very caustic business, with lots of nasty chemicals.
+Siskin's Bits and Bobs My ex-father in law, lets call him Gollum, used to do electroplating and he was very caustic and nasty, so there might be a correlation there.
An isolation transformer in the shore to ship mains connection and separation of the earthing systems seems to be the preferred solution used over here (NL). The galvanic isolator with justthe diodes in the earth connection might actually even be illegal. As a reaction to you remark towards heating systems. We also use radiators and water to heat buildings too, but usually the pipes are also made of steel. Not only is that cheaper than copper, it does away with the need for corrosion inhibitors, typically systems are simply filled with tap water. And it works well, the heating system in my appartment is as old as the 1960-ish building, and the only thing that has been replaced on a regular basis is the central heating boiler.
Thanks for video, Off to local marina today to do work and wondered what the principal of a galvanic isolator was, now I know! You are a similar chap to me, one minute playing with SMD components and the next minute playing with 125amp CEEform equipment, variety is the spice. Thanks for great videos 👌🏽
"Ayrth", what a beautiful pronunciation! An EXTREMELY interesting and informative video! Even people who repair/attach rain gutters can use this, especially if they're copper.
Fun fact: I just search for and found this specific video 2 years later. Because while I didn't need to know about it then, I find myself wanting to refer to it now. There is no such thing as useless knowledge.
Once upon a time there was a marina. This marina had a network of floating docks branching off. Also electrical service boxes fed from the shore with no GFCI protection. Two dock sections on different branches at the very end lost their flotation and half-sunk into the water. There were no electrical service boxes there (those sections used to tie visiting dinghies) so Management just shrugged, we'll fix it later, it was that kind of place. But unknown to Management the conduit along the underside to the very end terminating in a junction that was now underwater. Their electrical bill increased dramatically and they kept dunning their (fixed rate) customers to conserve energy. A friend of mine was an odd Brazilian chap and salvage diver, he'd freedive with weights and crawl around blindly waving his hands around in the marina muck under the docks and boats looking for Dropped Objects. He'd find them too, from tossed appliances to watches and jewelry. And VHF handie talkies, which he'd bring to me. "Can you fix this?" he'd ask. "Only on Day 1, maybe up to Day 7" I'd reply. I'd open the back and glance inside, invariably we were past Day 400... ANYWAY, he confided one day there were several places he felt a mysterious buzzing in his body, and he said "it makes the fish dance". Having experimented with electricity from a young impressionable age this send shivers up and down my spine. I called the marina and told them this was my last call to them, next time I'd call someone else, maybe the newspaper. Waddaya know, within a week there was brand new conduit strapped along the docks topside. Probably no GFCI, after all this was just the early '80s.
Very useful video, I had thought to do exactly the same to tackle earth loops in equipment. My only use of shore power on boats tends to be battery charging, the chargers all have floating output.
Good explanation. One comment however; when you were talking about the currents flowing in a larger system you mentioned that the currents would be much higher. This is of course true, but basically irrelevant. Rate of corrosion is relative to the current / area (in corrosion terms we talk about current density). The problem that had occurred on the boat that you showed pictures of was 'stray current localized corrosion' (apart from not being properly electrically protected, that is). Minor defects in the paint forced the current out at these locations. Since the absolute current and potential is, for all intents and purposes, constant and forced out at the relatively small defect areas, the current density at these spots gets quite high, and corrosion failure is the result. Ironically, if that part had not been painted, it would probably not have been punctured. It would have gotten rusty and ugly though.
Very interesting Clive. I am currently having a narrowboat built which we will be living on permanently in an inland marina. The boat will have both sacrificial anodes and a 'Sterling' galvanic isolator. Although I did have a very basic understanding of the rationale, thank you for creating this video and explaining in detail. You are absolutely right, the day has come where I need to get to grips with this stuff!!!!!!!!!!
Hi Clive, My father has on his steel boat a plug which supplies 50A 240VAC shore power. Inside, He has a set of two isolation transformers which step down to voltage to 120VAC mains as used in the US. One transformer feeds the 12V battery charger/inverter pass-through. The circuits powered from the inverter include a 20A circuit with several outlets around the boat, Television, Microwave. Lights are on a separate 20A circuit. The refrigerator runs off 12VDC from the battery charger, batteries, or one of the two alternators attached to the engine. The other transformer feeds the washing machine, air conditioners, hot water tank, and a single 120V outlet near the engine room. While under way, the 4-cylinder, 85 horsepower diesel engine is used to heat the water heater and charge the house battery banks via its two alternators. The circuits fed from the second transformer are unavailable when not docked. The transformer chassis' are connected to sure power ground. Everything inside the boat is on a floating ground with four zinc anodes bolted to the bottom corners of the hull as well as the prop. There is no ground connected to the dock except for the chassis' of the two transformers which are electrically isolated from the hull of the boat. Do you approve of this system? Thank you.
+Zach Z The only downside to the isolation transformers is that they weigh a lot. Particularly the ones for heavy loads. they also have modest losses which will result in extra running costs.
It can also protect your boat from other that have a electrical fault and have no zinc corrosion plates left on their hull (as a result of the fault) and can actually use another boats plates and wear them out.
Well, I learn something new every day watching this channel - even as a professional electronic engineer. In this case though, I realised he was going to use diodes before he said so. But I would never have thought of the solution had he not introduced the problem in the way he did.
I'm about to do your trick on my fibreglass boat as part of a mains circuit install and I was wondering if I should link the boat side of the shore earth to the engine 12v earth and thus the anode. Do I need to do other bonding? The fresh water tanks are SS but everything else is plastic.
Your coins and washers are only thinly plated with zinc and copper perhaps. What is underneath? Useful look-up terms include 'electrode potential', 'galvanic series'. Thanks for the videos, Clive.
Wondering what year that penny is. More recent pennies are about 97% zinc and 3% copper. Might be why the penny was quickly replated with copper and then started to dissolve to expose the zinc.
viebien79 UK pennies? Mostly steel, can be tested with a magnet (zinc would ignore it). Maybe you were speaking of American pennies, which I don't know.
Interesting. If I was tasked to do something like this (with no prior knowledge of the subject) I would probably used capacitors instead. However that would not allow inappropriate DC voltage to be ground. So only AC faults could be grounded. Inherently less safe than this method.
Lots of interesting points here Clive. You mentioned 'rapid corrosion'; my son fitted a Maplin wind turbine generator to his sailing boat, connections included crimped-on terminal lugs. After one month on the boat, no more power was being produced and there was a small blue stain on the deck where the lugs had been. I expect you have seen the many YT videos on electrolytic rust removal. I made such a set up and have cleaned many ancient workshop tools. You certainly get to see some unappetising red-brown soup in the process. If you haven't yet played with this, I'm sure you would enjoy it. I had some dealings with an Aberdeen firm called Corrocean Ltd. - they employ techniques based on this branch of science to protect N. Sea rigs.
+BigCliveDotCom. Don't forget to mention in bilges/engine rooms there could be fuel vapors. ∆V from loose or improper grounds can also provide spark potential. Another great Big Clive Production.
Ther are actually two slightly different forms of corrosion at work here; galvanic corrosion where dissimilar metals with different inherent potentials react in proximity and electrolytic corrosion where an external electrical source drives the reaction.
Clive, this is one of your very best, all new info for me! Thank you! As for folks complaining about your upload schedule, I would tell them they are lucky to have the benefit of your experience and knowledge at all. Piss on 'em. 😉
When I bought my Narrowboat many moons ago it was not fitted with a Galvanic Isolator and spent most of its time on shorepower - great for the batteries, not so hot for the hull. So I did a bit of research and plumped for ... an Isolation Transformer. More expensive than a GA but greater peace of mind.
Thanks Clive. Made me think of the disgusting 'snake oil' foot cleanser video. Out of interest, could I safely do this on my radiator earthing to reduce the damage to them over time?
This is a subject that also affects many a non-tupperware canal boat user (and brings out the"experts" that are either for or against anodes, or galvanic isolators, or having shore power at all, etc.), for the average dock-dweller on shore power and thought that GIs were for ninnies, they have to have their boat hauled out every few years to have new anodes fitted, CCers (Continuous Cruisers) don't have that issue as much as they use the engine to generate power or have either an onboard or a portable generator which they use on the boat (using on land would mean it was earthed, and brings back the isolation issues)... And electroplating is fun... :D
+bigclivedotcom Thank you for sharing this!!! I have posted a link to this video on a page I manage for my sailboat marina as you explain this concept quit well. not only have you clarified a few questions I have had for some time regarding galvanic corrosion but you also, perhaps inadvertently, clarified the roll of the bridge rectifier in my sailboats wind generator. Cheers Mate!!
Excellent description as always, Clive. When at Clydebank's finest, The RMS Queen Mary, I have noticed there are various corrosion protection systems in place to protect the 1000+ foot steel hull, in the sea water of the Long Beach harbor where she has been berthed since 1972. There are zinc blocks on the base of the berth, under the hull, and TRUs located at various places throughout the lower decks with cables exiting through the lowest portholes or other openings close to the waterline, connecting to what is underneath. Maybe to force a continuous DC potential between the ship's steel hull and the zinc anodes? It never occurred to me there would need to be isolation on the earth for the power supply. This enters the ship as 4,160 V, 60HZ, 3Ph to a transformer substation aboard the ship, which only the local electrical utility has access to. Since this could be close to 1,000 A with the load of a 400 room hotel and several restaurants and convention sites aboard, what would these diodes need to look like? Or would diodes still be used to isolate the ship from the wharf's earth? [Incidentally, this has worked quite well, the QM will be 80 years old on May 27, and diver inspections have found only thousandths of inches lost from the 2 inch thick hull.
+LakeNipissing I'm not sure how they would deal with that power. Even with full transformer isolation you would still have the potential for failure of the transformers or the cables feeding them.
Zinc based systems are usually passive. Electrically connecting the zinc and the hull sets up a cell where the zinc protects all the other metals while imposing a half volt or so of charge. For impressed current protection you want an anode that is much more durable (graphite, titanium, and stainless work well). You can have zinc anodes bonded to the protected item so that if the power supply fails there is still protection, and while the power is on the zinc would be protected as well, increasing the time before it needs to be replaced.
I knew you had to know about it, I wrote a post on your other video with the "Deadly quack water tester(scam)" and the whole time I was like, 'he definitely already knows about this, but I'll write a detailed post up anyway for others'. So hopefully I provided some inspiration. My personal experience with galvanic corrosion, was helping a friend cut out corrosion, and weld in aluminum squares, along a guys boat deck. After the drydock messed up, and used stainless steel bolts on his aluminum deck. Looked just like this upload.wikimedia.org/wikipedia/commons/7/7d/Stainless-steel-mild-steel.jpg All it takes is waves splashing up on the deck, and a few months later you're in a huge mess as your deck starts to separate from the hull.
I'm glad you mentioned the anti-corrosion components of automotive coolant/antifreeze. It's why the system should be drained, flushed, and refilled every so often, usually 5 years or 150,000 miles: the anti-corrosion additives become depleted, and it leads to failure of the radiator and heater core soon after. This is why when I buy used vehicles, I NEVER buy one which the owner added only plain water when it was low on coolant. You can usually tell by either asking the seller directly, or check for pitting around the fill cap.
+SigEpBlue If you ignore adding coolant antifreeze because you have a leaky system and just top up with plain water, there comes a point where components fail (because of the corrosion). In my case it was the water pump of a Volvo 240.
+SigEpBlue Bear in mind that at 80C water has a vapo(u)r pressure of 350 (torr/mmHg) and quickly ramps to 400 torr at 84C. Ethylene glycol has a vapo(u)r pressure of around 4 torr at 80C. 1 atmosphere of pressure is 760 torr. Topping off the expansion tank with water keeps the proportion closer to correct as the expansion tank is where you are going to see evaporation losses. Topping off with a 50/50 mixture will cause an increase in the concentration of ethylene glycol between coolant changes. edit: 5 years is an awful long time between coolant changes. I'd change it every autumn/winter if I lived in a hot or 4 season climate. Every other year in this mediterranean climate.
Markle2k 5 years was the recommended change interval given by Peak, for their "Long-Life" antifreeze. I'd suggest following the vehicle manufacturer's recommendations. If you're adding enough water to significantly throw the mixture off from 50/50, you have much bigger problems to worry about! :) FWIW, I live in West Michigan, and it's _definitely_ a four-season climate here: usually hits the mid-90s in July, and sub-zero during the harder winters. There's no reason I can see to change it more often, given a completely-sealed system, e.g. most vehicles I've driven since 2000 or so. If you have a system where the overflow is NOT pressurized (most older vehicles), then that might change. But I'd still go by the recommended interval.
SigEpBlue Agreed on the adding coolant thing. If you've got a leak in your pressurized system, you've got a problem that needs immediate fixing and the proportion is the least of your worries. I had a Honda Quaalude that would puke coolant out of the expansion tank in summer and after a lot of troubleshooting it turned out the previous owner (who kept logs) had put in a 190 degree thermostat (coffee can and thermometer test). A quick trip to the parts store for a $5 160 degree unit solved that. You'd have to leave the cap off the expansion tank to lose a lot if your car is in good shape. My point with the evaporation from the expansion tank was just that that was where you are going to lose coolant (mostly water) between changes if you don't have a leaky fitting or a cracked cylinder head or out of spec part. The plastic cap can't contain half an atmosphere of pressure. Modern 4-cylinders only hold about a gallon of coolant. The Honda Civic automatic's total coolant capacity is 4.1 liters including the 400cc in the expansion tank. So, getting out of balance isn't that hard. If you've got a 4.6 V-8 in an F-150 it has 4 gallons of coolant. Water has a higher heat capacity than m/ethylene glycol (EG), so running rich on the EG reduces the heat shedding ability of your cooling system. The EG's job is to raise the boiling point of the fluid so that you don't get vapor forming around your exhaust valves. Water _vapor_ has a much lower volumetric heat capacity than liquid H20/EG.
Keep coming back to this, as a boat owner I feel the price charged for these units is very expensive compared to the cost of the components. Anyway I've been reading up on this tonight as I was about to make one and there seems to be some that put a capacitor across the ac connectors of the bridge rectifier. Also a lot of concern about the diodes failing open circuit and basically breaking the connection to earth. Might put off my own attempts until I have done some more research .
When accelerate the reaction by applying current, if you're using sodium chloride salt in your water then the gas produced by electrolysis on the positive lead is going to contain chlorine gas. The concentration you get is not going to kill you, but it's not super great stuff inhale either.
mikeselectricstuff once did a teardown of a decommissioned bouy and that had a sacrificial electrode on to prevent all the other parts from corroding .... was pretty chewed up too
Nice one Clive, I am used to working on industrial electrics (ex.Instrument Tech.) I came across this problem recently when I put my boat in a Marina, I originally thought of isolating the transformer but some research led me to the galvanic isolator idea, the only problem with this setup is if the diodes fail they fail open and you lose your earth, this would be very unlikely as the rcd should trip on earth fault also, so are we looking at the different potential on earth here? the earth is bonded to the metal on the boat and that, in turn, is bonded to the sacrificial anodes. if this is the case you would always have a small current flow because of earth bonding. ?
+Peter Hasselström The galvanic isolation in that instance refers to the use of an isolation transformer. I first stumbled across the steelwork version while looking for information on transformer based galvanic isolators.
Thank you clive, for explaining a really interesting topic for us, as we live on a narrowboat. One question that remains, is if you added a second boat (or steel washer) which wasn't connected to the shore (or power supply), would the reaction take place on the unconnected one? Many thanks.
+marc harris If there's no connection to the shore ground then the circuit is not completed, so there is much less chance of corrosion. But localised corrosion can still occur between dissimilar metals connected together under water.
bigclivedotcom Thank you. We're off-grid, so its not so much of an issue for us, but an often disscussed topic between boaters. Even more enlightening was the difference in cost between 2 bridge rectifiers, and a box with 'boat magic' written on it! Thanks again, pint owed to you if you're ever in leicestershire. :)
It'd depend on what the boats are made of, I think, if they were both the same metal, nothing would happen. Since you're in fresh water, it's probably fine anyway, fresh water isn't great at passing current, even with the filth (and leptospirosis) in most canals. My mate had a cabin cruiser, but it was fibreglass. I met some very interesting people who live on canals though.
Small point but, on metal hull boats on Britain's inland waterways, the hull is NOT used as a 'neutral' terminal. There are separate conductors for L and N (or +ve/neg) for both 240v shore power and 12v dc supplies. The hull itself is obviously connected to mains earth. Clearly, galvanic corrosion is a function of the conductivity of the 'electrolyte' the boat floats in. Galvanic isolators are generally not used for boats used in inland and fresh water - Ive had five 3kg zinc sacrificial anodes on my canal boat which, over about 12 years, haven't shown the slightest alteration.
It's hard for me to do these types of experiments because they don't make pennies here anymore and most of them have been taken out of circulation. So random bits of copper aren't as plentiful as they once were. That's interesting at the end, though. I used some copper wires to generate hydrogen through electrolysis of water which I collected in a test tube held under the water, as you do. After a few days of storage, the water started to become discolored. I'm wondering if it has anything to do with the corrosion at the end of this video. Though the discoloration seemed to be coming from the cork stopper in the test tube, so I dunno. You wouldn't think there would be corrosion with similar metals, but as I recall, the stripped ends of the wire which were in the water had become very blackened and obviously corroded from my experiments.
The bridge rectifier with a shorted + and -, aka making it into 2 series resistors anti-parallel, is also frequently used in model railroads. It's used in occupancy detectors or current detectors to detect a train on a track instead of using 4 separate diodes.
+bigclivedotcom That would be fun to see you copper plate something. Question is what would be useful to copper plate? Something that needs to conduct heat or electricity. Or your 100k YT button. AVE electroplated his in gold. Fits his gold fever. Yours in copper would fit your electronics channel. PS-- clear spray lacquer will keep it from tarnishing afterwards.
+BikingMNViking That's when RUclips finally offer it. Apparently it can take a long time after you're reached 100,000 subscribers. Knowing my luck I'd connect the polarity wrong and electroplate a chunk of copper with my play button overnight
In Finland heating pipes are steel pipes so that the connection to a radiator is not two different metals. Water pipes (even warm water) are usually copper pipes though.
Aluminium shop fronts are usually heavily corroded by galvanic corrosion with steel structure or fasteners they are also at dog height so are usually fairly well connected to ground
So is this how the weird active galvanic protectors are supposed to work? i see some very very questionable devices that either put a small charge on the boat to offset the corrosion somehow, or they try to surround the boat in a power field (which I suspect is something that will never work given moving water would destroy the field). Also, it's strange to hear of a metal boat not using zincs.
+Selinica Harbinger Why? I think it's stranger not to think we could do anyway with changing radiator fluid so often if we just put in a 100k mileage sacraficial rod in a car's radiator system -- we do it home water heaters.
I had a home where we were on well water. The plumber did not install a ground lead on the pump and my copper home pipes became plagued with pin hole leaks day after day on different pipes. Came to terms with replacing every pipe in the home and then discovered why it was happening when I brought old pipes to the scrap yard and the man spotted the issue
I doubt that earthing had anything to do with it, what does cause real problems is mixing different metals, like steel and copper (even just fittings), or water ph and corrosiveness... better just to use pex multilayer pipe and brass fittings for drinking water, not worth using copper or steel
Hot water heaters have 1 or more anodes in them designed to corrode to prevent the other metals from corroding. It's also the reason why you are supposed to have the usually plastic washer connected to your water input and outputs to keep the different metals away from each other.
+John Doe No, those plastic isolaters are for heat loss. It if took care of the problem you would not need a sacraficial anode at all. What is annoying is why they make them all so hard to get to while electric water heaters have cheap and easy elements that go right through the side. That's how they should put in the sacraficial anode. You usually need an impact hammer to get one out so almost no one ever replaces one and justs lets the water heater go bad and eventually leak.
Serious question I had for years: is it possible to use this metchod to prevent road vechiles from rust? If yes, I would definetly put bar of zinc under my car.
I used a 12 volt car battery with a charger connected to de-rust steel parts for the restoration of my classic van. A plastic tub with soda crystals dissolved in water. The rusty parts are hung into the solution and connected to the negative. Then a sacrificial steel lump is dropped in connected to positive without touching, in a couple of days the rust leaves the pieces I want cleaning and deposits on the sacrificial steel.
Marina just cancelled my order as "you won't need it, electrician said, you could get the £2000 full isolation unit instead..." I just bought one off Amazon instead. Oh well. PS I doubt you could test these as they are often potted/epoxied for safety and water protection.
Fascinating video, but not the normal use of the term galvanic isolation, which means preventing any electrons from flowing from one side to the other, via capacitance, inductance, optical signal or other means. What is the resistance between two copper pipes 1 metre apart in dry Norfolk soil? I'd guess a lot more than 10 meg. And to complete a circuit to the substation? Gigs? For 240v to provide a 24mA trip current DC would take 10kohms or less . Surely soil resistance isn't that low.....I think our safety earths rely more on capacitive coupling.
The same thing is used for audio electronics.
The ground often gets connected between different amplifiers which have their own ground. (called ground loop) since it is a loop you will get an induced hum. Braking the loop is easy but often not safe. The diodes are an elegant and safe way to solve the issue.
interesting point
When applying current across your test set up, with polarity one way you were depositing a layer on the copper coin, effectively 'electro plating' the coin, with polarity reversed you are effectively removing a fine layer and 'electro brightening' the coin. (even with low current it would not take long for a measurable difference in thickness to be achieved) Galvanic deposition and corrosion are fascinating when you look at them in depth. I had to deal with galvanic corrosion when I worked with a marine engineering firm and got into electroplating while making parts for small engineering projects. (depositing protective layers on precision parts with various anodising processes) If you have a go at some basic electrolytic cleaning and electroplating with a variety of materials You will get a better feel for how nobility of metals makes a huge difference & galvanic corrosion will make way more sense :-) Galvanic corrosion also occurs between Carbon Fiber and various metals, this is why many carbon fiber products are made with a fiberglass 'separation layer' at fixing points. Titanium fixings should be used in preference to other metals such as steels or aluminium alloys as Ti is a closer match to the nobility of carbon which greatly reduces galvanic current flow and corrosion extending the working lifetime of the fixings and the carbon fiber. Experiment with some carbon fiber in a 'test tank' (also try different salts, acids and alkali solutions) and you will be pleasantly surprised at the results! :-) just be aware that you can produce a few rather iffy by-products while experimenting with electrolytic effects. fume extractor is a good plan. Take it steady & keep having fun!
That's now illegal in Finland and the coin dealers have started to use ultrasound cleaning of coins.
Sacrificial anode is connected to the hull. When I was in the petroleum business, we used galvanic protection to protect the fuel piping in old fueling stations before everyone changed over to double-walled fiberglass piping.
At the top of home water heaters you'll probably see a large bolt head. If you remove that while it is turned off and the water inlet valve is closed you'll see a corroded zinc rod or chain connected to it. That is a sacrificial rod designed to keep your water heater from consuming itself internally. If that rod completely dissolves, your water heater will start corroding and eventually leak.
A really interesting video Clive, its a shame they dont broadcast videos of this nature on television instead of the carp they publicly dispense, it would educate a lot more people instead of vegitating them with things like coronation street and eastenders. Well done.
+Phil Newman - Wait, TV is giving away free fish? ;-)
+RFC3514 There's Bellenders vids on YT too.
there's a french tv show that explains that
I'm addicted to this channel, and I'm not entirely sure why... I'm primarily concerned with software when it comes to computers. Must be what happens when you mix bears and electronics ;P
"So that's what's causing the Corro.......sion." said the electrical engi-bear.
"why the long pause?" asked the customer.
The engi-bear looks ashamed retracting his claws and says "I was just born this way."
Wow, I asked for your nautical tales and I got a 17 minute video! Very nice.
Very interesting Clive, I worked for British Telecom for many years and it was the eternal struggle to keep water out of the cables, using compressed air or grease and millions every year on new joint designs and testing. But an interesting thing is that they used a negative battery to power the lines. For several reasons, but the main one being electrolytic corrosion of the wires, mostly copper but still lots of Ali. The negative battery was supposed to stop the cables dissolving with the constant leaks in current to earth. Putting the meter across the pr showed -50v It wasn’t unusual to open a joint and find the Ali had turned to mush or was so thin it just crumbled. The copper was slightly more robust but still could be covered in green mush which was nicely conducting the current away to earth and the broard band and with it.. the fibre optics are much more reliable and replacing the copper at an incredible rate. There are sections of cable ( actually thousands of miles in total ) with 0.5mm copper to .5 Ali to .63 copper and back to Ali again with each connection, via crimps, changing the resistance, bits where engineers had split 2 prs and used the good leg of each to make a single pr, but now each leg being wrapped around a faulty leg instead of each other, this then causing broardband drop out and overhearing issues. Of course the ‘engineers’ are anything but these days so have no understanding of what or why they’re doing what they’re doing.
I only knew 'OF' this and didn't fully understand it...until now.
Thank you for the gift of knowledge, sir.
Thanks, found this video while researching galvanic isolators. I want to build one for my boat.
It's crazy that I had to go back to a video from 2016 from someone who basically never talks about boats to find this information. I kinda wish there were people in the youtube boating space that talked about stuff this in depth.
I worked as a commercial diver retrieving lost items, taking insurance photos, scrubbing hulls, fixing steering gear, you name it. Not one boat had an earth connection. They were all cut by the crew.
$5 to drink it! Now I'm aware of the difference between a galvanic isolator and a sacrificial anode... learn something every day!
Interesting. Normally I would think of galvanic isolation as making something electronically float with respect to another thing, so that no current can flow if you connect just one wire between any point of each end. Like transformers' secondary windings, which you can connect in series or parallel, like batteries. This diode trick, on the other hand, only prevents current flow when there's less than 1 volt of potential difference, so it's a very different thing. But I suppose the term "galvanic" isn't very strict, so it fits this concept as well.
It appears that I may have been using the term "galvanic isolation" incorrectly for 40 years. I also thought it meant to isolate the sides so there could be no current flow.
Clive, yet another good teacher you never had at school.
1:42 - "Here's a sea...which is a very large container of salt water..." That massive understatement made me laugh way more than is socially acceptable. :)
Clive, you are the inspiring science teacher I never had.
lazaglider v
I learned something new today! Actually I learn something new every time I watch your video. Easy to u derstand too! Keep it up.
I'd heard of sacrificial anodes, but not this. Very interesting. I feel like playing with electroplating now. My other half's dad used to do electroplating. Very caustic business, with lots of nasty chemicals.
+Siskin's Bits and Bobs My ex-father in law, lets call him Gollum, used to do electroplating and he was very caustic and nasty, so there might be a correlation there.
Watching new bigclivedotcom content when Clive mentions The Pirate Party Boat... wait, what!? That's moored like 500m in that direction!
An isolation transformer in the shore to ship mains connection and separation of the earthing systems seems to be the preferred solution used over here (NL). The galvanic isolator with justthe diodes in the earth connection might actually even be illegal.
As a reaction to you remark towards heating systems.
We also use radiators and water to heat buildings too, but usually the pipes are also made of steel.
Not only is that cheaper than copper, it does away with the need for corrosion inhibitors, typically systems are simply filled with tap water. And it works well, the heating system in my appartment is as old as the 1960-ish building, and the only thing that has been replaced on a regular basis is the central heating boiler.
Thanks for video, Off to local marina today to do work and wondered what the principal of a galvanic isolator was, now I know! You are a similar chap to me, one minute playing with SMD components and the next minute playing with 125amp CEEform equipment, variety is the spice. Thanks for great videos 👌🏽
"Ayrth", what a beautiful pronunciation!
An EXTREMELY interesting and informative video! Even people who repair/attach rain gutters can use this, especially if they're copper.
Fun fact: I just search for and found this specific video 2 years later. Because while I didn't need to know about it then, I find myself wanting to refer to it now.
There is no such thing as useless knowledge.
Once upon a time there was a marina. This marina had a network of floating docks branching off. Also electrical service boxes fed from the shore with no GFCI protection. Two dock sections on different branches at the very end lost their flotation and half-sunk into the water. There were no electrical service boxes there (those sections used to tie visiting dinghies) so Management just shrugged, we'll fix it later, it was that kind of place. But unknown to Management the conduit along the underside to the very end terminating in a junction that was now underwater. Their electrical bill increased dramatically and they kept dunning their (fixed rate) customers to conserve energy. A friend of mine was an odd Brazilian chap and salvage diver, he'd freedive with weights and crawl around blindly waving his hands around in the marina muck under the docks and boats looking for Dropped Objects. He'd find them too, from tossed appliances to watches and jewelry. And VHF handie talkies, which he'd bring to me. "Can you fix this?" he'd ask. "Only on Day 1, maybe up to Day 7" I'd reply. I'd open the back and glance inside, invariably we were past Day 400... ANYWAY, he confided one day there were several places he felt a mysterious buzzing in his body, and he said "it makes the fish dance". Having experimented with electricity from a young impressionable age this send shivers up and down my spine. I called the marina and told them this was my last call to them, next time I'd call someone else, maybe the newspaper. Waddaya know, within a week there was brand new conduit strapped along the docks topside. Probably no GFCI, after all this was just the early '80s.
Very useful video, I had thought to do exactly the same to tackle earth loops in equipment. My only use of shore power on boats tends to be battery charging, the chargers all have floating output.
Good explanation. One comment however; when you were talking about the currents flowing in a larger system you mentioned that the currents would be much higher. This is of course true, but basically irrelevant. Rate of corrosion is relative to the current / area (in corrosion terms we talk about current density).
The problem that had occurred on the boat that you showed pictures of was 'stray current localized corrosion' (apart from not being properly electrically protected, that is). Minor defects in the paint forced the current out at these locations. Since the absolute current and potential is, for all intents and purposes, constant and forced out at the relatively small defect areas, the current density at these spots gets quite high, and corrosion failure is the result. Ironically, if that part had not been painted, it would probably not have been punctured. It would have gotten rusty and ugly though.
+Left Flamingo That's the same phenomen that works on your teeth's mercury amalgam fillings. My smaller ones always had higher voltages.
Very interesting Clive. I am currently having a narrowboat built which we will be living on permanently in an inland marina. The boat will have both sacrificial anodes and a 'Sterling' galvanic isolator. Although I did have a very basic understanding of the rationale, thank you for creating this video and explaining in detail. You are absolutely right, the day has come where I need to get to grips with this stuff!!!!!!!!!!
Hi Clive,
My father has on his steel boat a plug which supplies 50A 240VAC shore power. Inside, He has a set of two isolation transformers which step down to voltage to 120VAC mains as used in the US. One transformer feeds the 12V battery charger/inverter pass-through. The circuits powered from the inverter include a 20A circuit with several outlets around the boat, Television, Microwave. Lights are on a separate 20A circuit. The refrigerator runs off 12VDC from the battery charger, batteries, or one of the two alternators attached to the engine. The other transformer feeds the washing machine, air conditioners, hot water tank, and a single 120V outlet near the engine room. While under way, the 4-cylinder, 85 horsepower diesel engine is used to heat the water heater and charge the house battery banks via its two alternators. The circuits fed from the second transformer are unavailable when not docked. The transformer chassis' are connected to sure power ground. Everything inside the boat is on a floating ground with four zinc anodes bolted to the bottom corners of the hull as well as the prop. There is no ground connected to the dock except for the chassis' of the two transformers which are electrically isolated from the hull of the boat.
Do you approve of this system?
Thank you.
+Zach Z The only downside to the isolation transformers is that they weigh a lot. Particularly the ones for heavy loads. they also have modest losses which will result in extra running costs.
It can also protect your boat from other that have a electrical fault and have no zinc corrosion plates left on their hull (as a result of the fault) and can actually use another boats plates and wear them out.
It's just now 9 pm here. He is uploading to his North American viewers. Thanks
What an elegant and simple solution with those diodes.
Well, I learn something new every day watching this channel - even as a professional electronic engineer. In this case though, I realised he was going to use diodes before he said so. But I would never have thought of the solution had he not introduced the problem in the way he did.
I'm about to do your trick on my fibreglass boat as part of a mains circuit install and I was wondering if I should link the boat side of the shore earth to the engine 12v earth and thus the anode. Do I need to do other bonding? The fresh water tanks are SS but everything else is plastic.
Sea: noun. A very large container of salty water. Oxford dictionary. 😂
Your coins and washers are only thinly plated with zinc and copper perhaps. What is underneath? Useful look-up terms include 'electrode potential', 'galvanic series'. Thanks for the videos, Clive.
Wondering what year that penny is. More recent pennies are about 97% zinc and 3% copper. Might be why the penny was quickly replated with copper and then started to dissolve to expose the zinc.
viebien79 UK pennies? Mostly steel, can be tested with a magnet (zinc would ignore it). Maybe you were speaking of American pennies, which I don't know.
I'd have done so much better in school if I had these videos back then. So informative and easy to understand!
Thank you.
Learned something new today. Thanks Clive.
Interesting. If I was tasked to do something like this (with no prior knowledge of the subject) I would probably used capacitors instead. However that would not allow inappropriate DC voltage to be ground. So only AC faults could be grounded. Inherently less safe than this method.
Lots of interesting points here Clive. You mentioned 'rapid corrosion'; my son fitted a Maplin wind turbine generator to his sailing boat, connections included crimped-on terminal lugs. After one month on the boat, no more power was being produced and there was a small blue stain on the deck where the lugs had been.
I expect you have seen the many YT videos on electrolytic rust removal. I made such a set up and have cleaned many ancient workshop tools. You certainly get to see some unappetising red-brown soup in the process. If you haven't yet played with this, I'm sure you would enjoy it.
I had some dealings with an Aberdeen firm called Corrocean Ltd. - they employ techniques based on this branch of science to protect N. Sea rigs.
Thanks Clive. My brother's narrowboat has 6 chunky magnesium sacrificial anodes, which last about 3 years.
+BigCliveDotCom. Don't forget to mention in bilges/engine rooms there could be fuel vapors. ∆V from loose or improper grounds can also provide spark potential. Another great Big Clive Production.
Ther are actually two slightly different forms of corrosion at work here; galvanic corrosion where dissimilar metals with different inherent potentials react in proximity and electrolytic corrosion where an external electrical source drives the reaction.
You always upload when I've cracked my first beer. Awesome.
Manky, that's a great word I've not heard in a while. Fascinating video, thank you.
Clive, this is one of your very best, all new info for me! Thank you! As for folks complaining about your upload schedule, I would tell them they are lucky to have the benefit of your experience and knowledge at all. Piss on 'em. 😉
When I bought my Narrowboat many moons ago it was not fitted with a Galvanic Isolator and spent most of its time on shorepower - great for the batteries, not so hot for the hull. So I did a bit of research and plumped for ... an Isolation Transformer. More expensive than a GA but greater peace of mind.
lol, this is a youtube TREASURE!...much thanks, learned an incredible amount.
Thanks Clive. Made me think of the disgusting 'snake oil' foot cleanser video. Out of interest, could I safely do this on my radiator earthing to reduce the damage to them over time?
This is a subject that also affects many a non-tupperware canal boat user (and brings out the"experts" that are either for or against anodes, or galvanic isolators, or having shore power at all, etc.), for the average dock-dweller on shore power and thought that GIs were for ninnies, they have to have their boat hauled out every few years to have new anodes fitted, CCers (Continuous Cruisers) don't have that issue as much as they use the engine to generate power or have either an onboard or a portable generator which they use on the boat (using on land would mean it was earthed, and brings back the isolation issues)...
And electroplating is fun... :D
Yay!! I was really hoping for a follow up vid! Awesome stuff!!!
+bigclivedotcom Thank you for sharing this!!! I have posted a link to this video on a page I manage for my sailboat marina as you explain this concept quit well. not only have you clarified a few questions I have had for some time regarding galvanic corrosion but you also, perhaps inadvertently, clarified the roll of the bridge rectifier in my sailboats wind generator. Cheers Mate!!
Excellent description as always, Clive. When at Clydebank's finest, The RMS Queen Mary, I have noticed there are various corrosion protection systems in place to protect the 1000+ foot steel hull, in the sea water of the Long Beach harbor where she has been berthed since 1972. There are zinc blocks on the base of the berth, under the hull, and TRUs located at various places throughout the lower decks with cables exiting through the lowest portholes or other openings close to the waterline, connecting to what is underneath. Maybe to force a continuous DC potential between the ship's steel hull and the zinc anodes? It never occurred to me there would need to be isolation on the earth for the power supply. This enters the ship as 4,160 V, 60HZ, 3Ph to a transformer substation aboard the ship, which only the local electrical utility has access to. Since this could be close to 1,000 A with the load of a 400 room hotel and several restaurants and convention sites aboard, what would these diodes need to look like? Or would diodes still be used to isolate the ship from the wharf's earth? [Incidentally, this has worked quite well, the QM will be 80 years old on May 27, and diver inspections have found only thousandths of inches lost from the 2 inch thick hull.
+LakeNipissing I'm not sure how they would deal with that power. Even with full transformer isolation you would still have the potential for failure of the transformers or the cables feeding them.
Zinc based systems are usually passive. Electrically connecting the zinc and the hull sets up a cell where the zinc protects all the other metals while imposing a half volt or so of charge. For impressed current protection you want an anode that is much more durable (graphite, titanium, and stainless work well). You can have zinc anodes bonded to the protected item so that if the power supply fails there is still protection, and while the power is on the zinc would be protected as well, increasing the time before it needs to be replaced.
+bigclivedotcom there is no fuckery with the ground, they use energized sacrificial electrodes
cheers Clive. Thats another new thing I have learnt from watching your channel :)
When I was young it was common(ish) to coat small motorcycle parts with zinc using this method, powered by a car battery.
Very Interesting! Thanks! Thumbs up!
This is not the first time I watch one of your videos but this one made me hit the subscribe button. I'm not sure why I didn't do it before.
Intriguing indeed! Great video as always Clive, keep it up :)
I knew you had to know about it, I wrote a post on your other video with the "Deadly quack water tester(scam)" and the whole time I was like, 'he definitely already knows about this, but I'll write a detailed post up anyway for others'.
So hopefully I provided some inspiration.
My personal experience with galvanic corrosion, was helping a friend cut out corrosion, and weld in aluminum squares, along a guys boat deck. After the drydock messed up, and used stainless steel bolts on his aluminum deck.
Looked just like this
upload.wikimedia.org/wikipedia/commons/7/7d/Stainless-steel-mild-steel.jpg
All it takes is waves splashing up on the deck, and a few months later you're in a huge mess as your deck starts to separate from the hull.
I'm building an alarm for my boat. This is one additional circuit sensor for it !
I'm glad you mentioned the anti-corrosion components of automotive coolant/antifreeze. It's why the system should be drained, flushed, and refilled every so often, usually 5 years or 150,000 miles: the anti-corrosion additives become depleted, and it leads to failure of the radiator and heater core soon after. This is why when I buy used vehicles, I NEVER buy one which the owner added only plain water when it was low on coolant. You can usually tell by either asking the seller directly, or check for pitting around the fill cap.
+SigEpBlue If you ignore adding coolant antifreeze because you have a leaky system and just top up with plain water, there comes a point where components fail (because of the corrosion). In my case it was the water pump of a Volvo 240.
+SigEpBlue Bear in mind that at 80C water has a vapo(u)r pressure of 350 (torr/mmHg) and quickly ramps to 400 torr at 84C. Ethylene glycol has a vapo(u)r pressure of around 4 torr at 80C. 1 atmosphere of pressure is 760 torr. Topping off the expansion tank with water keeps the proportion closer to correct as the expansion tank is where you are going to see evaporation losses. Topping off with a 50/50 mixture will cause an increase in the concentration of ethylene glycol between coolant changes.
edit: 5 years is an awful long time between coolant changes. I'd change it every autumn/winter if I lived in a hot or 4 season climate. Every other year in this mediterranean climate.
Markle2k 5 years was the recommended change interval given by Peak, for their "Long-Life" antifreeze. I'd suggest following the vehicle manufacturer's recommendations. If you're adding enough water to significantly throw the mixture off from 50/50, you have much bigger problems to worry about! :)
FWIW, I live in West Michigan, and it's _definitely_ a four-season climate here: usually hits the mid-90s in July, and sub-zero during the harder winters. There's no reason I can see to change it more often, given a completely-sealed system, e.g. most vehicles I've driven since 2000 or so. If you have a system where the overflow is NOT pressurized (most older vehicles), then that might change. But I'd still go by the recommended interval.
SigEpBlue Agreed on the adding coolant thing. If you've got a leak in your pressurized system, you've got a problem that needs immediate fixing and the proportion is the least of your worries. I had a Honda Quaalude that would puke coolant out of the expansion tank in summer and after a lot of troubleshooting it turned out the previous owner (who kept logs) had put in a 190 degree thermostat (coffee can and thermometer test). A quick trip to the parts store for a $5 160 degree unit solved that.
You'd have to leave the cap off the expansion tank to lose a lot if your car is in good shape. My point with the evaporation from the expansion tank was just that that was where you are going to lose coolant (mostly water) between changes if you don't have a leaky fitting or a cracked cylinder head or out of spec part. The plastic cap can't contain half an atmosphere of pressure.
Modern 4-cylinders only hold about a gallon of coolant. The Honda Civic automatic's total coolant capacity is 4.1 liters including the 400cc in the expansion tank. So, getting out of balance isn't that hard. If you've got a 4.6 V-8 in an F-150 it has 4 gallons of coolant. Water has a higher heat capacity than m/ethylene glycol (EG), so running rich on the EG reduces the heat shedding ability of your cooling system. The EG's job is to raise the boiling point of the fluid so that you don't get vapor forming around your exhaust valves. Water _vapor_ has a much lower volumetric heat capacity than liquid H20/EG.
Awesome channel by the way. Thanks Clive.
Keep coming back to this, as a boat owner I feel the price charged for these units is very expensive compared to the cost of the components. Anyway I've been reading up on this tonight as I was about to make one and there seems to be some that put a capacitor across the ac connectors of the bridge rectifier. Also a lot of concern about the diodes failing open circuit and basically breaking the connection to earth. Might put off my own attempts until I have done some more research .
Well, thank you for this information....I found it very interesting :)
thank you for making the knowledge useful and memorable. i appreciate it :D
When accelerate the reaction by applying current, if you're using sodium chloride salt in your water then the gas produced by electrolysis on the positive lead is going to contain chlorine gas. The concentration you get is not going to kill you, but it's not super great stuff inhale either.
This is actually very relevant because I'm thinking of buying a narrowboat.
Very interesting being a plumbing and heating engineer watching this
mikeselectricstuff once did a teardown of a decommissioned bouy and that had a sacrificial electrode on to prevent all the other parts from corroding .... was pretty chewed up too
fantastic! we got a tripple-whammy today!
On my car I’ve just had the metal rad pipes replaced. Caused by dissimilar metal corrosion. All models of the cars of my year have it now.
Nice one Clive, I am used to working on industrial electrics (ex.Instrument Tech.) I came across this problem recently when I put my boat in a Marina, I originally thought of isolating the transformer but some research led me to the galvanic isolator idea, the only problem with this setup is if the diodes fail they fail open and you lose your earth, this would be very unlikely as the rcd should trip on earth fault also, so are we looking at the different potential on earth here? the earth is bonded to the metal on the boat and that, in turn, is bonded to the sacrificial anodes. if this is the case you would always have a small current flow because of earth bonding. ?
My DAC has galvanic isolation on its USB input. Nice to know it would prevent the DAC from corroding if I tossed my computer in the sea.
+Peter Hasselström The galvanic isolation in that instance refers to the use of an isolation transformer. I first stumbled across the steelwork version while looking for information on transformer based galvanic isolators.
Thank you clive, for explaining a really interesting topic for us, as we live on a narrowboat. One question that remains, is if you added a second boat (or steel washer) which wasn't connected to the shore (or power supply), would the reaction take place on the unconnected one? Many thanks.
+marc harris If there's no connection to the shore ground then the circuit is not completed, so there is much less chance of corrosion. But localised corrosion can still occur between dissimilar metals connected together under water.
bigclivedotcom
Thank you. We're off-grid, so its not so much of an issue for us, but an often disscussed topic between boaters. Even more enlightening was the difference in cost between 2 bridge rectifiers, and a box with 'boat magic' written on it! Thanks again, pint owed to you if you're ever in leicestershire. :)
It'd depend on what the boats are made of, I think, if they were both the same metal, nothing would happen. Since you're in fresh water, it's probably fine anyway, fresh water isn't great at passing current, even with the filth (and leptospirosis) in most canals. My mate had a cabin cruiser, but it was fibreglass. I met some very interesting people who live on canals though.
Small point but, on metal hull boats on Britain's inland waterways, the hull is NOT used as a 'neutral' terminal. There are separate conductors for L and N (or +ve/neg) for both 240v shore power and 12v dc supplies. The hull itself is obviously connected to mains earth. Clearly, galvanic corrosion is a function of the conductivity of the 'electrolyte' the boat floats in. Galvanic isolators are generally not used for boats used in inland and fresh water - Ive had five 3kg zinc sacrificial anodes on my canal boat which, over about 12 years, haven't shown the slightest alteration.
It's hard for me to do these types of experiments because they don't make pennies here anymore and most of them have been taken out of circulation. So random bits of copper aren't as plentiful as they once were. That's interesting at the end, though. I used some copper wires to generate hydrogen through electrolysis of water which I collected in a test tube held under the water, as you do. After a few days of storage, the water started to become discolored. I'm wondering if it has anything to do with the corrosion at the end of this video. Though the discoloration seemed to be coming from the cork stopper in the test tube, so I dunno. You wouldn't think there would be corrosion with similar metals, but as I recall, the stripped ends of the wire which were in the water had become very blackened and obviously corroded from my experiments.
The bridge rectifier with a shorted + and -, aka making it into 2 series resistors anti-parallel, is also frequently used in model railroads. It's used in occupancy detectors or current detectors to detect a train on a track instead of using 4 separate diodes.
Funny, my class just learned about galvanic cells today :D
Thanks for the extra insight into how it's of use :)
+Dominic C. It's actually easier to understand when you see a real world application. Pure theory is boring and hard to remember.
+bigclivedotcom I agree completely!
bigclivedotcom 100%
It's just gibberish the way they explain it now. Thy should use your example of the boat.
Have you thought about removing the copper from your old etching fluid using electrolysis?
+Green Silver I've been looking at Nurd Rage videos regarding that, but amen't really etching enough boards to try it at the moment.
+bigclivedotcom That would be fun to see you copper plate something. Question is what would be useful to copper plate? Something that needs to conduct heat or electricity. Or your 100k YT button. AVE electroplated his in gold. Fits his gold fever. Yours in copper would fit your electronics channel. PS-- clear spray lacquer will keep it from tarnishing afterwards.
+BikingMNViking That's when RUclips finally offer it. Apparently it can take a long time after you're reached 100,000 subscribers. Knowing my luck I'd connect the polarity wrong and electroplate a chunk of copper with my play button overnight
This is an interesting topic which i've never thought or heard of before :)
Clive in a hot pursuit of Alessandro Volta!
In Finland heating pipes are steel pipes so that the connection to a radiator is not two different metals. Water pipes (even warm water) are usually copper pipes though.
Aluminium shop fronts are usually heavily corroded by galvanic corrosion with steel structure or fasteners they are also at dog height so are usually fairly well connected to ground
I believe copper oxide forms a passivating layer, so it takes a bit for the electrons to poke back through when the power is hooked back up.
Is there any damage caused by having too much AC on your ground line or is the time delay from that plating/unplating effect protecting everything.
The same thing happens with cheap watch straps/ jewellery, the alloys along with sweat react and can irritate skin.
So is this how the weird active galvanic protectors are supposed to work? i see some very very questionable devices that either put a small charge on the boat to offset the corrosion somehow, or they try to surround the boat in a power field (which I suspect is something that will never work given moving water would destroy the field).
Also, it's strange to hear of a metal boat not using zincs.
+Selinica Harbinger Why? I think it's stranger not to think we could do anyway with changing radiator fluid so often if we just put in a 100k mileage sacraficial rod in a car's radiator system -- we do it home water heaters.
well done, haven't seen a quality video on your channel like this one for sometime. :bd
Many thanks for this I still haven't got round to buying a Galvanic isolator for my narrowboat :/
I had a home where we were on well water. The plumber did not install a ground lead on the pump and my copper home pipes became plagued with pin hole leaks day after day on different pipes. Came to terms with replacing every pipe in the home and then discovered why it was happening when I brought old pipes to the scrap yard and the man spotted the issue
I doubt that earthing had anything to do with it, what does cause real problems is mixing different metals, like steel and copper (even just fittings), or water ph and corrosiveness... better just to use pex multilayer pipe and brass fittings for drinking water, not worth using copper or steel
Brass usually has some lead in it (added to increase machineability) but a very few fittings could be OK I guess
Hot water heaters have 1 or more anodes in them designed to corrode to prevent the other metals from corroding. It's also the reason why you are supposed to have the usually plastic washer connected to your water input and outputs to keep the different metals away from each other.
+John Doe No, those plastic isolaters are for heat loss. It if took care of the problem you would not need a sacraficial anode at all. What is annoying is why they make them all so hard to get to while electric water heaters have cheap and easy elements that go right through the side. That's how they should put in the sacraficial anode. You usually need an impact hammer to get one out so almost no one ever replaces one and justs lets the water heater go bad and eventually leak.
Also applies to PC water cooling. Sometimes you have a CPU block made of Aluminium, and a GPU block made of copper.
I know almost nothing about electricity and what a boring subject anyway. Having said that, these videos are always interesting and so well explained.
?
Serious question I had for years: is it possible to use this metchod to prevent road vechiles from rust? If yes, I would definetly put bar of zinc under my car.
How about a conductive walkway? Do they isolate these aswell or is ground leakage not that big of a problem then?
I used a 12 volt car battery with a charger connected to de-rust steel parts for the restoration of my classic van. A plastic tub with soda crystals dissolved in water. The rusty parts are hung into the solution and connected to the negative. Then a sacrificial steel lump is dropped in connected to positive without touching, in a couple of days the rust leaves the pieces I want cleaning and deposits on the sacrificial steel.
Excellent
Rtd Ship Engineer
Marina just cancelled my order as "you won't need it, electrician said, you could get the £2000 full isolation unit instead..."
I just bought one off Amazon instead. Oh well.
PS I doubt you could test these as they are often potted/epoxied for safety and water protection.
Fascinating video, but not the normal use of the term galvanic isolation, which means preventing any electrons from flowing from one side to the other, via capacitance, inductance, optical signal or other means. What is the resistance between two copper pipes 1 metre apart in dry Norfolk soil? I'd guess a lot more than 10 meg. And to complete a circuit to the substation? Gigs? For 240v to provide a 24mA trip current DC would take 10kohms or less . Surely soil resistance isn't that low.....I think our safety earths rely more on capacitive coupling.