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Blue Chromate Plating
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I am a young Mechanical Engineer at a heavy manufacturing plant, I am fairly new to the game and I am very inexperienced in materials finishes. I have a customer spec calling out a blue chromate finish for a part. Can anybody give me a brief description of this and if possible some references where I can goto to learn more. I am planning on hitting up the library to reference the ASM collection, is that a good enough resource or is there a better resource out there?
Kevin Engelstad- West Fargo, North Dakota, USA
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You have encountered an example of lingo or trade venacular, Kevin, and it can indeed be hard to get your bearings in such cases. As a young engineer involved in surface finishing, please give strong consideration to attending a local AESF meeting (www.nasf.org) if possible. You do not need to be a member, you will be welcomed, and you will rub shoulders with "old hands" who will be delighted to answer your every question in whatever detail you need. If you can get to "Sur/Fin" this year, you can attend the industry's largest exhibition and conference.
To answer your question without further misleading you can be tricky, but I'll try. Many components are zinc plated for corrosion resistance. But the zinc in turn can quickly "white rust". To deter this, zinc plated components are almost always chromate conversion coated, and that chromate can have several colors -- black, iridescent yellow, and blue being examples. The blue is a slightly blue toned bright metallic finish, it is certainly not blue in the sense of blue paint. Traditionally these chromate coatings have involved hexavalent chromium. These days they are usually trivalent to comply with RoHS requirements.
So what does "blue chromate plating" mean? Almost surely it means zinc plating followed by a blue-toned chromate conversion coating, hopefully trivalent chrome. Our "must have" booklist is more targeted towards these processes than simply starting at ASM. Good luck.
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 Ted Mooney, P.E. RET finishing.com Brick, New Jersey |
December 20, 2011
Q. Thanks for your article about the Blue Chromate. I am struggling with a cost associated with blue chromate and I am considering taking the product and converting it to Stainless. My customer is concerned about the conductivity of stainless with respect to that of Blue Chromate.
Ron
Engineer - Armagh, Pennsylvania, USA