Galvanizing process : Hot dipping (Corrosion control)

Describes the galvanizing process/hot dipping. The types of hot dipping methods are listed. It discusses the surface treatment, galvanizing and post-treatment steps. It discusses how zinc is coated on iron or any other corrosive metal. Mentions the uses of this method. It also explains the users of this method. Why did stuffs cannot be stored in galvanized containers is also explained.
Hot Dipping: Galvanizing
You will be able to
define hot dipping and discuss the two types.
list out the surface treatment of galvanizing process.
describe the process of galvanizing and post treatment steps.
enumerate the uses this method.
mention the drawback of using galvanized containers to store food stuffs.
Hot dipping
Hot dipping is a process of coating the base metal (metal with higher melting point) by dipping into a bath containing molten coating metal (metal with lower melting point)
Types of Hot dipping
Galvanizing : Anodic Coating- Coating of more active metal (less standard reduction potential) over less active metal (more standard reduction potential). eg. Coating zinc over copper, iron, steel etc.
Tinning : Cathodic Coating- Coating of less active metal (more standard reduction potential) over more active metal (less standard reduction potential). eg. Coating tin over copper, iron, steel etc.
Galvanizing process
Galvanizing is a process of coating the base metal (metal with higher melting point) by dipping into a bath containing molten coating metal (metal with lower melting point).
Surface preparation
DEGREASING/CAUSTIC TREATMENT
Caustic/Alkaline solution: Removes dirt, oil grease
PICKLING
Dilute HCl or H2SO4 : Removes oxides and scales
FLUXING
ZnCl2/NH4Cl : Protective layer to prevent oxidation of the base metal
DRYING
Hot air : Reduces splash and increases dip speed
Galvanizing
Galvanizing kettle
Molten metal 98% Zn
Temperature 438 - 460 oC (820-860 oF)
Dipping Time ~10 minutes
Galvanized Coating
Post treatment
Quenching Water and chemicals to form passivation layer to protect galvanized component
Removal of zinc drips or spikes by grinding
Uses of galvanisation/galvanizing
Galvanized steel wires, pipes, nails, screws, nuts and bolts.
Galvanized steel frames and roof tops for construction.
Door frames, window frames and bars.
Domestic applications such as washing machine, hair dryers, trimmers, computer parts, AC housings etc.
Protective gears, high way signs, high tension electric towers
Galvanized containers cannot used to store food stuffs, as zinc dissolves especially when acidic food is stored and poisons the food.

[@leonardo-fp7on]

thank you for the clear explanation!

[@RevathiPurushothaman]

Thank you.

[@krishanmohansharma8306]

Great explanation thanks for sharing 👍👍👍

[@RevathiPurushothaman]

Thank you very much.

[@navneetbatish4986]

Thanks. All doubts cleared.

[@RevathiPurushothaman]

Most welcome.

[@ajitsende1401]

Good explanation

[@RevathiPurushothaman]

Thank you.

[@hudaansari5195]

Very helpful. Thank u😊

[@RevathiPurushothaman]

Most welcome.

[@Royalsteelgalvanizers]

Vry usefull knowledge sharing

[@RevathiPurushothaman]

Thank you so much.

[@brglobaltrade562]

Hi Good Morning. Thanks for the information. Wanted to clarify what is the timing duration for rinsing/fluxing/zinc molten bath ? Can you also provide information on electro galvanizing process ?

[@vasavi7230]

Thanks a lot.

[@RevathiPurushothaman]

You are most welcome.

[@prudhviraj9087]

thanks a lot
nice presentation

[@RevathiPurushothaman]

Most welcome. Thank you.

[@preethas6415]

Thank u mam.. this is very clear !!

[@RevathiPurushothaman]

Thanks.

[@khaledmohamed234]

Thanks for your good information

[@RevathiPurushothaman]

Most welcome.

[@RevathiPurushothaman]

Most welcome.

[@satheeshselvaraj1996]

Superb explanation mam! Do more videos! It will be more useful.

[@RevathiPurushothaman]

Thank you.

[@MrRawnik]

Well explained

[@RevathiPurushothaman]

Thank you.

[@sakthishsakthi5715]

SO NICE

[@RevathiPurushothaman]

Thank you.

[@samersamir8940]

Thanks for useful presentation, but i can't tinning copper cos tin is more activity than copper. Also the definition of hot dipping applying for galvanizing only cos there is a reverse relation between metal activity and milting point. Right? ☺

[@marishakrishna]

Thanks for the videos...further to it post galvanizing details of dicromating in details could have been mentioned

[@RevathiPurushothaman]

Even I like to include all the details I know, unfortunately people are not interested in watching long videos. Thanks for your suggestion.

[@JinnTheExplorer]

Nice dear

[@RevathiPurushothaman]

Thanks.

[@flamingpxv9469]

Next day is my science exam 😅

[@meenasharma704]

Nice knowledge about Galvenizing
Please give information about patella effects

[@RevathiPurushothaman]

Thank you. Sure.

[@Indiansports421]

Can u telle how to make cold phosphate chemical for grey colour coating?

[@jaikumarsaini7776]

Thanks mam u r great...

[@RevathiPurushothaman]

Thank you.

[@krunalmehta1687]

thanks

[@RevathiPurushothaman]

Most welcome.

[@zeeshan4376]

Pls tell us galvanizing brightener making?

[@ramakrishnan6913]

You said quenching is done in water and chemicals to form a passive layer.
Will you please explain in detail. Its not clear to me.

[@georgephilip6622]

The drying or preheating processing before Galvanization is not only to avoid splash but also to avoid thermal expansion/ thermal shock which can cause deformation of the metal component to be dipped

[@RevathiPurushothaman]

Thank you very much for enlightening me all those who watch this video.

[@suthanprasad]

very interest to know mam

[@RevathiPurushothaman]

Thank you.

[@arunkiran1985]

Hello Mam,
Thank you for very clear explanation.
I have doubt, what is the duration for each step in this galvanizing process?

[@elbuggo]

She said the metal had to stay in the zinc bath for 10 minutes. Then you can calibrate those other steps for 10 minutes too. If the acid hasn't removed all oxidation within 10 minutes, add some more acid, etc.

[@MINX7EM]

love this but need to upgrade sound or put words in convocation

[@RevathiPurushothaman]

Thanks for your suggestion. Audio is updated.

[@Karthik-ut3vo]

Hello Ravathi mam, its very informative presentation. Thank you! I have a questions. You mentioned that zinc coated utensils should not used for storing food items. But how could i find if a zinc coating done when a utensils i select from store?

[@RevathiPurushothaman]

You need not worry. Cooking and storage containers are normally coated with tin. It is harmless. When we purchase stainless steel and aluminium vessels, it will never be coated. Zinc coating will be grey in colour like your galvanized iron screws (GI).

[@Karthik-ut3vo]

@@RevathiPurushothaman Thank you for clarifications mam :-)

[@RevathiPurushothaman]

Most welcome.

[@amarnathgattu1333]

Mam from last one year we changed two kettles , two kettle are used only five month each. What is life of kettle ? Why kettle are puncher for what reason ?

[@prabhatmishra9979]

👍

[@georgephilip6622]

After quenching there is one more process of dipping it in a deoxidation tank so that we can prevent White Rust and White rust is especially likely to form on newly galvanized material. This is because the new zinc coating has not yet had the chance to form the stable oxides, and the hydrogen and the oxygen bond with the pure zinc which forms zinc hydroxide .

[@RevathiPurushothaman]

Thank you very much for enlightening me all those who watch this video.

[@ramakrishnan6913]

I only guess that , there is a post treatment given .the part is quenched in a tank of water and chemicals to form passive layer.
In that context may be the above process of deoxidation is not required. I am not sure but its only a guess.

[@ramakrishnan6913]

When the part is passed through the zinc chloride flux and then dried and finally dipped in zinc. Doesn't this dilutes the zinc molten bath,

[@RevathiPurushothaman]

It will not dilute.

[@harshpatil4524]

this is good but in this video,diagram of hot dipping of galvanizing should similar the diagram used in hot dipping of tinning.

[@RevathiPurushothaman]

Thanks for your suggestion. I purposefully gave different diagrams for galvanizing and tinning. The diagram for tinning will hold good for both galvanizing and tinning, for the writing exams. But practically in industries, the diagram used for galvanizing is adopted. So, I thought the students should know both. What ever is the diagram, the concept remains the same. The material to be coated should go into each tub. Anyway I am happy that you have expressed your opinion.

[@ramakrishnan6913]

Can we store food stuffs of alkaline nature or not.

[@RevathiPurushothaman]

It is better not to store food stuff in galvanized containers.

[@amreshkumarsingh3529]

Good Morning to all. I, AMRESH KUMAR SINGH. My Reg. No.-CCW217

[@RevathiPurushothaman]

Thanks for your participation.

[@amitshaw5053]

Chemical ratio and dipping time is need to mentioned.. With this its look like therory class.

[@RevathiPurushothaman]

Thanks for your suggestion.

[@amitshaw5053]

Madam can you mention on reply these are the parameters??

[@RevathiPurushothaman]

Go through this content. You will get the full details. All details cannot be informed in one youtube video. This video was done for students, not for commercial purpose. www.iitk.ac.in/ce/test/IS-codes/is.2629.1985.pdf

[@devranjankumar6666]

U are genius

[@RevathiPurushothaman]

Thank you. But nobody is genius in this world. It is just the sharing of information.

[@lpsag9652]

New information give me

[@zeeshan4376]

Formula

[@venkatachalamurthy4551]

madam I want study course related to galvanising any courses are available in india give information of college

[@RevathiPurushothaman]

No idea. Sorry.

[@manithuligal6918]

Need a Tamil explanation please..

[@RevathiPurushothaman]

I will try in future.

[@jamestai3390]

we are galvanizing kettle factory.

[@latheshkc2097]

Dear James,
Could you please share your contact details to send enquires for kettle for electric and diesel fired furnace .

[@jamestai3390]

@@latheshkc2097 [e-mail]

[@MDANWAR-lx2ns]

Very low voice

[@RevathiPurushothaman]

The audio issue is rectified in later videos.

[@mahalaxmitubes9488]

Super ... Mail I'd plz

[@RevathiPurushothaman]

Thank you.