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Hardcoat Anodize 7075 Aluminum on Ampco 45 1
- Thread starter fuzion
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Are you concerned with galvanic corrosion?
What is the application/exposure?
Generally, copper is one of the worst accelerators of corrosion of aluminum. Even rainwater running off Cu roofing corrodes Al. But, Aluminum Nickel Bronze, Alloy C630 is the 'least bad' of the Cu alloys. However, 7075 is about the 2nd most corrosion-prone of the common wrought Al alloys (after 2024). The hard anodizing of the 7075 will delay the inevitable, but I wouldn't recommend the given combo for a longterm outdoor application.
What is the application/exposure?
Generally, copper is one of the worst accelerators of corrosion of aluminum. Even rainwater running off Cu roofing corrodes Al. But, Aluminum Nickel Bronze, Alloy C630 is the 'least bad' of the Cu alloys. However, 7075 is about the 2nd most corrosion-prone of the common wrought Al alloys (after 2024). The hard anodizing of the 7075 will delay the inevitable, but I wouldn't recommend the given combo for a longterm outdoor application.
Adding to "kenvlach's" post is that a major use for Ampco 45 is valve guides in Aluminum heads for high performance engines. Just saw one where the Ampco 45 guide sees the cooling water in the engine. This water has a very good inhibitor and I saw no corrosion.
Don't think about salt water.
If you could comeback with what media the combination will see I think you will get a more specific answer.
Don't think about salt water.
If you could comeback with what media the combination will see I think you will get a more specific answer.
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Even tough Aluminum can be used as a bearing the are some parameters that have to be met.
It has to be lubricated and the PV keep a low as possible.
Aluminum at high speeds is goverened by the oil film.
I’ll try to find my information on aluminum bearings and get back. I don’t remember ever remember encountering an aluminum bearing with the bearing surface anodized.
Hardcoat anodizing can be very abrasive so watch you joint carefully.
It has to be lubricated and the PV keep a low as possible.
Aluminum at high speeds is goverened by the oil film.
I’ll try to find my information on aluminum bearings and get back. I don’t remember ever remember encountering an aluminum bearing with the bearing surface anodized.
Hardcoat anodizing can be very abrasive so watch you joint carefully.
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I would test this long and hard before committing to production.
“Teflon®-impregnated hard anodize” is basically a myth. The pores are too small even for the submicron particles used, and there is a surface charge problem. Ergo, MIL-A-63576A ALUMINUM OXIDE COATING, LUBRICATIVE, FOR ALUMINUM AND ALUMINUM ALLOYS was canceled without replacement in 1998.
For those anodizers who claim to co-deposit Teflon® during the anodizing process, this is basically not true, either. See
A. D. Dinsmore et al., Nature, vol. 383, p. 239 (1996), or
J. M. Runge and A. Pomis, Plating & Surface Finishing, p. 60-64 (June 2003).
The latter paper describes experimental work in which an unspecified ‘electroactive polymer’ was co-deposited with hard anodize. This process has not yet been commercialized to my knowledge.
Alternatives: liquid or dry-film lubricants such as baked-on Teflon® can be used on unsealed hard anodize. Or, electroless nickel containing co-deposits such as Teflon® particles can be plated on aluminum.
“Teflon®-impregnated hard anodize” is basically a myth. The pores are too small even for the submicron particles used, and there is a surface charge problem. Ergo, MIL-A-63576A ALUMINUM OXIDE COATING, LUBRICATIVE, FOR ALUMINUM AND ALUMINUM ALLOYS was canceled without replacement in 1998.
For those anodizers who claim to co-deposit Teflon® during the anodizing process, this is basically not true, either. See
A. D. Dinsmore et al., Nature, vol. 383, p. 239 (1996), or
J. M. Runge and A. Pomis, Plating & Surface Finishing, p. 60-64 (June 2003).
The latter paper describes experimental work in which an unspecified ‘electroactive polymer’ was co-deposited with hard anodize. This process has not yet been commercialized to my knowledge.
Alternatives: liquid or dry-film lubricants such as baked-on Teflon® can be used on unsealed hard anodize. Or, electroless nickel containing co-deposits such as Teflon® particles can be plated on aluminum.
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