You didn't mention the base metal of the battery bracket.  Is it plated steel or aluminum?  What is the color of the chromate?  Clear, yellow, black?  Clear is the thinnest followed by yellow,  olive drab and black.  Is the bracket plated and if so with what metal?  If it's plated it's likely zinc on steel.  Doubtful cadmium would be used unless for some reason it was spec'd.

If I were to hazard a guess it's possible that the cloudy appearance is from the underlying base metal and not the chromate.  If that's the case then your corrosion protection, as measured by a salt fog chamber, should be OK.  Chromates are thin, largely gelatinous coatings containing metal salts, water and both hexavalent and trivalent chrome.  They are created in a chemical reaction where the dissolution of the base metal is integral in forming the coating.  The coating sets and dries pretty quickly and eventually goes away with time.

Roger Mouton
EIMC Advanced Plating Technologies

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg
Sent: Friday, September 02, 2016 7:45 AM
To: [log in to unmask]
Subject: [TN] Chromate coatings

Hi Technetters! Getting ready for the long weekend (at least here in the US)?

I'm looking for some advice on chromate coatings. We produce a phone for mining applications, which uses a battery held in by a bracket. The bracket is chromate coated. 

The most recent batch of brackets sent out to the coating house came back with a cloudy appearance to the coating. Apparently something hiccupped in their process. The process can't be repeated, so we either scrap the parts and make new ones, or use them as is. Problem is, I don't know if the cloudy appearance will affect the corrosion protection properties. Any chromate experts out there that can offer any advice on this?

Thanks,
Blair


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