What is stress corrosion? Stress corrosion cracking/Stress cracking: Electrochemical Corrosion

This explains the stress corrosion and the conditions. Three different mechanisms involved in stress corrosion. Explains caustic embrittlement, season cracking, hydrogen embrittlement. Preventive measures of stress corrosion.
Stress Corrosion/Stress Cracking/Stress Corrosion Cracking
You will be able to define stress corrosion.
You will be able to enumerate the conditions and causes for stress corrosion.
You will be able to explain the mechanism of stress corrosion with special cases .
You will be able to suggest the preventive measures for stress corrosion.
Stress corrosion
Stress corrosion occurs due to the tensile stresses (applied stress and residual stress) on the susceptible material in the presence of a specific corrosive environment, resulting in the formation of crack which propagates.
Causes of Stress corrosion
Susceptible metal Specific corrosive environment
Copper alloys NH3 and ammonia compounds
Mild steel Alkalis and nitrates
Stainless steel Chlorides and acid chlorides
Causes of Stress corrosion
Due to stresses caused by heavy machining works in fabricated articles of certain alloys
Rolling
Drawing
Insufficient annealing
Cold or hot bending
Welding
Mechanism
Embrittlement
Caustic embrittlement
Hydrogen embrittlement.
Active Path Dissolution
Film induced cleavage
Caustic embrittlement
in high pressure steam boilers
Carbon and low alloy steels - in the presence of
caustic solutions, nitrates, phosphates, carbonates
Na2CO3(used for water softening) present in boiler feed water decomposes
NaOH flows into hair cracks of boiler walls by capillary action and reacts with iron to form sodium ferroate
Season cracking in copper alloys
Due to high residual stresses caused by cold working in fabricated articles of brass in the presence of ammonia or amines.
Dissolution of brass in ammonia leads to intergranular corrosion
Hydrogen embrittlement
Hydrogen being small, dissolves in all metals and diffuse between metal atoms in the crystal lattice.
Active Path Dissolution
Eg. Precipitation of chromium carbide over stainless steel.
Chromium concentration is low along the grain boundaries (susceptible region) - less passivated (anode) - corrosion occurs
Unstressed region - more passivated (cathode)
Film induced cleavage
Brittle film over ductile metal-Crack induced in the film and propagates into ductile metal -If brittle film is formed due to corrosion process, it repeats till transgranular fracture occurs
Prevention of stress corrosion
Avoid specific chemical environment.
Control operating temperature.
Control stresses while machining.
Choose materials which do not react with the specific chemical environment.

[@shubhamupman7260]

Thank you Mam. Yours was the only proper explanation for Stress corrosion I found. Thank you for clearing this concept!! 🙏🙏

[@RevathiPurushothaman]

It's my pleasure. You are most welcome.

[@svanitha3272]

Good explanation and lectures are very apt for the online workshop

[@RevathiPurushothaman]

Thanks for your compliment. This motivates us to do more.

[@ramakrishnan6913]

Some more details if added may be this topic for more clarity

[@unknownfacts3215]

Very nice explained

[@RevathiPurushothaman]

Thank you.

[@kollibalakrishna314]

Thank you very much for the nice presentation

[@RevathiPurushothaman]

It's my pleasure.

[@myteacher4976]

Gud....

[@RevathiPurushothaman]

Thanks

[@andippankavitha2509]

Nice presentation 👍

[@RevathiPurushothaman]

Thanks a lot

[@sameerabanu5848]

Mam you are very good teacher

[@RevathiPurushothaman]

Thanks for your compliment.

[@waleedeng8287]

thank you so much
do you have hand book about that ?

[@RevathiPurushothaman]

Its my pleasure.

[@bhargavanaidu8470]

Thank you professor

[@RevathiPurushothaman]

Most welcome

[@ramakrishnan6913]

hydrogen embrittlement is loss of ductility of material due to absorption of hydrogen. Next
you said there are stress in intergrannular cracks .

[@suthanprasad]

Very informative mam

[@RevathiPurushothaman]

Thank you very much for your sincere response.

[@unknownfacts3215]

Thank you very much mam

[@RevathiPurushothaman]

Most welcome.

[@pankajkumarpandey6658]

Excellent

[@RevathiPurushothaman]

Thank you so much.

[@pankajkumarpandey6658]

@@RevathiPurushothaman dear madam Revathi. I really enjoyed your lecture. Why it is stress corrosion, this I came to know after long long time and this I wanted to know. You have cleared very nicely. Please upload more lectures.

[@RevathiPurushothaman]

Sure. Thank you so much for your support.

[@RevathiPurushothaman]

Sure. Thank you so much for your support.

[@iyyappans36]

Good presentation mam

[@RevathiPurushothaman]

Glad you liked it. Thank you.

[@ramakrishnan6913]

if compressive stress acts , will not there be stress corrosion.

[@stressfreepro6529]

all the best :)

[@RevathiPurushothaman]

Thank you.

[@gkpatilpatil6588]

Good morning to all, Gangadhar Kishanrao Patil, ACS College Shankarnagar Tq Biloli Dist Nanded Maharashtra

[@mustapham6890]

I have a question if I may ask Professor,
Transgranular and Intergranular are types of Scc or they are considered the way the stress propagates? And if they are not considered as types of Scc what are the types of Scc?
Thanking you in advance :)

[@aravindkumar6631]

Corrosion types are seperated based on their appearance it has nothing to do with mode of fracture

[@sushmithaprabakaran]

@@aravindkumar6631 some of the damage mechanism have particular mode like branching crack , finger print crack, non branching crack , transgranular and intergranular

[@21afridi]

Sorry to say. Kindly correct "environment" pronunciation.

[@RevathiPurushothaman]

Sorry, Thanks for your correction. I will see to it that it is not repeated in future.

[@21afridi]

@@RevathiPurushothaman thanks i do not want to be Grammer nazi but it irritates during listing and drivert attention. Your lectures are very good. Hope to see more.

[@yashkoshy9654]

Didi thoda zor se bola karo yaar

[@RevathiPurushothaman]

I have rectified this issue in future videos.

[@ganeshmhaske8181]

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