Topic: Zinc plating

The guys I work with tell me: Zinc plate and Yellow Chromate and Trivalent Zinc Yellow are the same thing.  Is this correct and if not, what is the difference?  nancys


Re: Zinc plating

I'm not sure what you mean.  There are 2 common types of chromate conversion coatings for zinc plating: hexavalent and trivalent.  Hex-based coatings were typically iridescent and/or yellow, due to the color or hex chrome in solution.  Trivalent-based coatings are clear/blue, again due to the color of the trivalent chrome in solution. Sometimes it is possible to add a yellow dye to the trivalent process, which gives a yellow color.  In general, the hex-based chromates provide more corrosion resistance at a cheaper price, but many locales have placed limitations on the use of hex chrome.  The trivalent alternatives often work as well as the hex versions, but tend to cost a bit more.  A few years back, when the high-performance trivalents were not at readily available, many spec sheets called for a yellow chromate, without reference to trivalent or hexavalent.  Now, the word "yellow" is being phased out in preference to actual performance specs and/or "trivalent" or "hexavalent".

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer


Sanford, NC


Re: Zinc plating

I am facing problem in electroplating steel wires dia 0.50 mm.I am using:

Boric Acid

Zinc sulphate

sodium sulphate

amonia sulphate.

Ph 2.5 Degree 30 Bath is 19.5 feet 1100 liter.

But quality is not satisfactory. 20 wires pass through the bath the same time.

I request to experts what can i do.