Summary for red rust on tin plated parts Discussion
Red rust on tin plated parts is discussed as most likely a coverage problem in the deep bore. In the original question, S Venkatachalam describes an En1A(L) component with a complex internal bore and a Cu undercoat plus tin finish, yet severe red rust appears in the deepest bore area. Khozem Vahaanwala Saify replies that the rusting is probably caused by no plating coverage in the bore and recommends cross-sectioning a sample part to verify how much coating actually reaches the deep areas. The thread also includes a second, related question about Cu-Ni-Tin plating on CRCA steel turning red rust after 48 hours, but no answer is shown for that follow-up. Overall, the practical takeaway is to inspect coating thickness and continuity in the bore before changing the process, because poor penetration or no deposit in recessed areas is the most likely cause.
Q. We are tin plating a component,with outer dimensions of Dia. 25 mm X length 35 mm, and with bore region which start from Dia. 20 mm X 9 mm depth,and then M18Thread X 7 mm depth,then further cone region dia 13 X dia. 10 X 5 mm depth, and altogether the total depth the bore region extends around 24 mm deep.
Plating Spec. Base Metal – En1A(L), Undercoating – Cu (min 5 micron), Tin – Min 6 micron
Our Process : Kerosene Cleaning- Alkaline Cleaning – Electro cleaning
– Acid picking – cyanide copper – Acid Tin – ovan Drying.
We have severe red rust problem in bore region, at deeper area. What could be the causes?
How those causes would cause red rust? What are recommendation to eliminate this red rust?
S Venkatachalam
auto components – Chennai, India
2006
A. The rusting is probably the result of no plating coverage in the bore. I would suggest starting by cross-sectioning a sample piece and seeing what kind of plating coverage you have down there.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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2006
2006
A. Agreed. Acid Tin plating thickness will build up rapidly on the outer surfaces and Acid Tin baths require a lot of care and tweaking in order to plate recesses like these.
You need to also ensure proper fixturing to plate the recesses or may also want to try Alkaline Tin Plating for such parts.
Khozem Vahaanwala
Saify Ind
Bengaluru, Karnataka, India
Rusting of Cu-Ni-Sn plated steel
Q. My situation: we use cu+ni+tin plating for rust prevention for CRCA.
But after 48 hours it’s becoming red rust. Why is this happening?
Muttabattula Kranthi
– Hyderabad. Telangana, INDIA
July 21, 2018
Ed. note: We’re not seeing the rust. Can you tell us where it is and perhaps send a close-up of it?