Metal finishing Q&As since 1989

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Chem film Class 3 the beginnings

I work at a small company and we were looking in to doing some class 3 chem filming of our own. we have been unsuccessful with find what type of materials/supplies we would be needing for doing this on our own. We are planning on filming aluminum and that is all, but like I said we would like to know what we need, and maybe some help with the process. If you could help that would be great but I understand your time constraints. thanks have have a great day.

Brian Mcarthur
- Grand Rapids, Michigan, US
2007

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Chem filming, also called chromate conversion coating, is usually done per MIL-DTL-5541 [on DLA]F -- so start by getting a copy of that standard, Brian. Next a book on finishing of aluminum such as Robert Probert's inexpensive "Aluminum How-To" or "The Surface Treatment and Finishing of Aluminum and its Alloys". From your reading you will realize that the chem-filming step per se is only one step in a process that also includes cleaning, etching, and desmutting. The chemicals used for chem filming are virtually always proprietary (in fact you can't do mil-spec chem filming except with chemicals that are on the QPL-81706 [on DLA] qualified products list), so usually you can get assistance from the process supplier.

These days there is tremendous pressure against putting hexavalent chromate on the parts, so I would suggest that you plan on chrome-free conversion coating (if you do not require Mil-DTL-5541 compliance, and TCP chromating if you do. Good luck with it.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

adv.