Letter 5081

NON CHROMATE CONVERSION COATINGS 

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I am looking for ANY information you may have on non-chromate conversion coatings, specifically for aircraft apllications. I am working with the Cdn. air force on alternatives to alodining. All responses are greatly appreciated.

Ben Whiting
- Ottawa, Ontario, Canada

Greetings Ben,

A group of us discussed this topic in the anodizing forum a while back on basically the faults that non-chrome conversion coatings have over their hexavalent chromium comparisons. They do provide for excellent paint bases, that part still applies, but the corrossion resistence #'s compared to hex chrome conversions are not even close, I want to say on the order of 1/4 of the amount of salt spray compared to the hex chrome ones.

I wish I could remember the article # exactly but I'm sure if you search the archives you'll find something.

Matthew Stiltner
- Toledo, OH

Ben:

This is a very delayed response to your question of 17 May, but I hope it will be useful. We are aware of the problems and wondered if you have considered a hard nickel coating?

We are a Canadian company and also have some work on-going for aerospace applications. The direction is to replace chome with hard nickel - either as a coating, or, for some applicaions, making the parts in pure nickel with a hardened surface. This is quite feasible in our gas process, because the deposition of nickel is one continuous process, during which the gas mixture can be altered to the client's specifications. So you get a hard surface backed up by normal (pure) nickel, as thick as needed.

Our business specializes (since 1987) in CVD of nickel, nikel alloys and other metals. We can grow nickel (as a coating, or as a net shape) inside cavities, inside tubes or cans, and we reproduce very fine surfaces, such as optical or bio-science equipment parts consistently.

I hope this helps. Please let me know if you need more information.

Sincerely

Mick O'Meara
- Toronto, Canada

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