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Oven Dry For Chromate

2006

Dear all,

We encountered problem that yellow residue were found from yellow chromated parts. It is believed that the residue is caused by improper drying and curing process.

Is aluminum conversion coating suitable for oven drying?
What is the appropriate temperature for drying (i) Yellow Chromate (ii)Clear Chromate

And what is the curing time required for yellow chromate parts?

Please advise.

Chen Yuet Hiong
Electroplating - Singapore

An oven would work but it is the maximum temperature that is critical. The chromate film is basically a gel layer and excess temperature will dehydrate this film and cause it to powder. Any method of heated drying should not exceed 120-130 °F.

Gene Packman
process supplier - Great Neck, New York
2006

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2006

This is the situation that we are facing:

Part Assembly:
Yellow Chromate part was assembled together with anodised + powder coating part.

Hypothesis:
i) Excess chromate residue on the part was transferred to Portdoor (anodised + powder coating part) under high humidity. High humidity is possible as unit is wrapped in plastic bag under air con environment and shipped via air.

ii) Yellow Chromate part were cleaned with IPA dipped white cotton and yellow stain found on the cotton.

Queries:
1) Is it normal that yellow chromate surface will dis-colourised under high temperature and humility ?

2) Is IPA cleaning a correct method to clean the surface of yellow chromate part?

3) What is the drying temperature and curing hour/temperature for yellow Chromate, under MIL-C-5541 ?

4) Is there any specification on curing requirements for mil-c-5541, yellow?

5) Is there a replacement for chrome-free gold / yellow color aluminium conversion coating?

Chen Yuet Hiong
Electroplating - Singapore