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Galvanize vs yellow chromate

We are a manufacturer of toxic gas monitors for the semiconductor industry. we have always specified a clear Iridite or yellow chromate finish on our metal components. One of our suppliers is changing their finish from yellow chromate to galvanized. I was wondering if the electrical properties of the galvanize are similar to the yellow chromate? We rely heavily on the grounding of internal components to control radiated RF emissions and susceptability. While working on getting the machine certified for emissions and such, I was surprised at how much change could be achieved by simply tightening a screw. So now I am worried that the change in coating may require retesting. Has anyone had any experience with this? I'm sure I'm just over reacting, but would like to hear any feedback.

Thanx,

Rubens Chiluk
manufacturer of gas monitors - Lincolnshire, Illinois, USA
2004

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My suspicion is that, this being a semiconductor application, your supplier wants to reduce the possibility of the formation of zinc whiskers by switching from an electroplated to a galvanized finish. But galvanized finishes are usually clear chromated, similarly to zinc electroplated finishes, so I don't think it will be a problem. Unfortunately, I can't think of a precedent, so I don't have real experience to fall back on here in case there is some distinction I'm missing.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

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2004

Mr Rubens,

If this is a simple case of replacing a finish, with another , then Alkaline Cyanide Free zinc may provide the right answer.

APART FROM THE VERY UNIFORM COVERAGE AND EXCELLENT DUCTILITY, THE MOST IMPORTANT ASPECT IS THAT aLK zINC EXHIBITS A COLUMNAR MICROSTRUCTURE WHICH MOST READILY ACCEPTS AND FORMS THICK YELLOW CHROMATE PASSIVATED LAYERS THAT LAST MUCH LONGER THAN THOSE FROM OTHER SYSTEMS. Deposit thicknesses of 35 to 55 microns are entirely possible. ALK ZINC , IN MY EXPERIENCE HAS REPLACED HOT DIP GALVANISING :

TWO EXAMPLES

1) ON CEILING FAN DOWN RODS. 1976 AND 2001.. DELHI FARIDABAD.
2) ON FENCE POST FITTINGS. CHANDIGARH. NORTH INDIA. 2001.

REGARDS,

Asif Nurie [deceased]
- New Delhi, India
With deep regret we sadly advise that Asif passed away on Jan 24, 2016

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I can understand Rubens problem. I have the same problem. It is tied in with surface conductivity. A long path for RF currents for EMC creates high radiation. I have the same problem, and need to know more about the various passivating processes and their effect on SURFACE CONDUCTIVITY. This is not to be confused with bulk conductivity which is what concerns safety standards.

What are the passivating compounds formed by chromating, and other passivating finishes, and what is their resistivity. With the tightening of standards for both metal finishing and EMC, this is a potential problem area.

Ian Juniper
Office products - Harlow, Essex, UK
2004