MIL-C-5541
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United States Military Specification MIL-C-5541 describes chromate conversion coatings for aluminum and its alloys. The current specification, MIL-DTL-5541F, superseded MIL-C-5541E in July 2006. Though designed to be used for US military subcontractors, it has gained world wide use across many fields due to the clear way it has been set out as opposed to the more verbose ISO equivalent.
There are two classes of coating:
- Class 1 A - This is a thick coating for use as a final finish or pre-treatment to paint or powder coating. This is gold, brown or yellow depending on coating weight and alloy.
- Class 3 - This is a thin coating for low contact resistance. The coating weight is lower as is the corrosion resistance. There may be some advantages using this thinner film in bonding applications. This film will appear to be a lighter color of gold.
Note: Depending on which chemfilm product you may use, for example, L25 or 1600 colors will vary from green, gold, and purple colors.
The specification covers pre and post treatment and the proprietary chemicals approved for the conversion coating process.
The British equivalent is Def Stan 03/18.
