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Specifying MIL-DTL-5541 chemical conversion coating 1

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Tunalover

Tunalover

Mechanical
Mar 28, 2002
1,179
The latest version of Subject standard defines two types of chemical: Type 1 and Type 2. These types determine if the chemical contains hexavalent chromium. The older version of the spec specified only classes of treatments: Class 1A and Class 3, for example, determine the thickness of the surface treatment. What if one does not specify the Type of treatment and instead calls out only the Class of treatment? What Type of treatment is received by default? Or is the specification incomplete in that there is no default defined?


Tunalover
 
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From MIL-DTL-5541F CHEMICAL CONVERSION COATINGS ON ALUMINUM AND ALUMINUM ALLOYS

3. REQUIREMENTS
3.1 Materials. If no material type is specified type I shall be used. Unless otherwise specified in the contract or order, substitutions of either type I for type II, or type II for type I coatings are not permitted.
 
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Aren't there prohibitions against hexavalent chromium in the Type 1, though?

TTFN

FAQ731-376
 
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IRstuff RoHS and similar legislation don't like the type 1 with the hexavalent chromium. I don't believe there's any specific legislation in the US that directly affects it but for exporting to europe, China etc. it can be an issue.

Be aware, that the last I looked into it, some colors weren't available in Type 2, most obviously the classic gold color.

Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​
 
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Our last few contracts all had prohibitions against hexavalent chromium, among others.

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FAQ731-376
 
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Just had a quick look and it doesn't look like there's a federal/USA wide RoHS directive (yet).

However some states have something similar (or at least ours by the looks of it).

Also, it wouldn't surprise me if DoD etc. aren't pre-empting it.

For example I know in the UK the MOD didn't like Cadmium plating on new stuff, or even on new production runs of existing kit, even though at the time there wasn't a legal ban.

Posting guidelines faq731-376 (probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​
 
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