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How to detect whether it's Zinc or Cad or Chrome
(-----) March 29, 2011
Q. Good Day,
We buy, make and sell fasteners of all types and sizes. What I am looking for is a spot check kit that will allow me to check and verify that we do in fact have zinc plating, or cadmium plating, or chrome plating. I know that in most instances the blue hue or yellow hue will give an indication of zinc or cad, but I'd like a litmus test.
At one time Systems Scientific Laboratories had a spot check kit where when drops of the prescribed chemicals from the kit were put on a litmus type paper, then the fastener (or whatever) put on the chemical spot, the resulting color that appeared on the paper told the story. I cannot locate Systems Scientific and have been told they no longer are in business.
Thanks for your time.
Fastener maker/distributor - Cleveland, Ohio, US of A
April 25, 2011
A. I used to have platers who purchased used Cadmium ball anodes to save money. Many times there were zinc ball anodes comingled. I took an eyedropper with Conc. Hydrochloric Acid and placed a drop or two on the anode in question. I allowed it to drip down onto a white porcelain plate, and added a drop or two of 10% Sodium Sulfide under a fume hood. If the liquid turned yellow, we had Cadmium (Yellow Cadmium Sulfide.) If it turned white, we had Zinc. (White Zinc Sulfide). A good rinse and the ball anode could be used.
Alternatively, a good X-Ray thickness tester can be used to determine the metal.
NOTE: Used Anode Balls should be washed thoroughly, just in case there might be dried cyanide residue on the surface. Use good chemical handling techniques with this work.
Ed Budman [dec]
With deep sadness we advise that our friend Ed passed away Nov. 24, 2018
April 27, 2011
A. Hi Mitch,
We have had a similar problem at my company. In the end, so that we didn't have to play with any chemicals we bought a hand held X-Ray Fluorescence machine. It is an excellent tool for detecting the coating present and now the inspectors swear by the technique.
Just one way to solve your problem.
Aerospace - Yeovil, Somerset, UK