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Aluminum corrosion while touching stainless steel 304




Q. I have aluminum touching stainless steel 304. Should I anodize the aluminum or to do other process in order to prevent corrosion.

Danny Krausz
- Tel Aviv, Israel
1999



March 1, 2009

A. Hi, Danny. Bare aluminum usually has little corrosion resistance, so you must do something. Yes, anodizing is a good corrosion resistant finish, and sufficiently dielectric to help a good deal in the galvanic corrosion issue.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey



Q. I have aluminum touching stainless steel 304. Should I anodize the aluminum or should I do a different process in order to prevent the corrosion. Why does the aluminum corrode?

Brent Galas
automotive - Lincolnshire, Illinois, USA
2004


A. Anodise, or better, Zinc- Cobalt plate the Aluminum.

Khozem Vahaanwala
Khozem Vahaanwala
Saify Ind
supporting advertiser
Bengaluru, Karnataka, India
saify logo
2004


A. Hi, Brent. The aluminum corrodes because the stainless is more "noble", which means that when there are corrosive forces tending toward dissolving the stainless steel, it will "steal" electrons from the aluminum so that aluminum atoms are converted from neutral metal to positively charged aluminum ions which dissolve into solution. Ideally the two metals should not touch, but should have plastic insulation between them (although that can't always be done).

Khozem has a great deal more hands-on experience than I have, so I'm always reluctant to disagree with him. But I will say that anodizing may be better depending on the circumstances. If the zinc-cobalt plated aluminum area is very much larger than the stainless steel area, the galvanic corrosion force from the stainless will be distributed over a large area and perhaps not contribute much to corrosion. However, if the plated aluminum area is small compared to the stainless steel area, a large galvanic force will be distributed over a small plated area, so I think the plating will quickly corrode away. Anodizing on the other hand, if free from damage, is an effective insulator so there will be no galvanic forces. Plus, I think anodizing is much simpler and more reliable than plating aluminum. Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 2, 2013




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