blue chromate question

[R.B.]

I mixed up my blue chromate solution today... have a few questions about it. I went with the recc. mix of 8oz blue chromate to 1 qt distilled water.

I plated a few small parts in my copy cad (old style solution) and it all looked fairly normal, with the part AND the little hanging wire having a silver color whereever it was submerged when plating. Then I dipped into the blue chromate for 35 seconds and quick cold rinse, then hot blow dry with a heat gun.

I was surprised to see the wire that HAD turned to a silver color after the copy cad dip, had now turned back to copper color. It was as if the blue chromate removed the copy cad plating?? VERY strange. The part that I was plating did not really change much in appearance, maybe a bit darker. I tried it a couple more times, with the same results.

Has anyone else seen this?

thanks,
rb

[seanc]

R.B.

Haven't seen this myself, but if you're using a heat gun, you might be getting it too hot. Chromates do NOT like excessive high temperatures. Caswell Blue is maximum 150º.

I occasionally use a heat gun too, but I "calibrated" it. Using a thermometer, I held the heat gun at different distances from the thermometer, until I found the right distance for 140º. It turned out to be 3-3.5 feet for my gun!

Sean