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"Bright gold plating is fine, but matte finish gold plating fails corrosion testing"
March 24, 2017
Q. I have a client whose product requires a brushed gold electroplating finish on steel that can withstand high temperature (up to 450 deg;F) and some chemical resistance (liquid products used in hair salons) during normal use. The current product is finished in bright gold electroplating on top of nickel and copper, and has worked well for over 20 years. The client wants to change the finishing to brushed finish gold to match their new brand aesthetics.
We have tested many samples out of their factory in China, most of which failed basic salt spray/fog test. As the factory explained to me, they started out with a clean steel finish on wheels, and leaving the polish marks on by either eliminating or reducing the copper & nickel layers before finishing in gold. The looks is very close to what the client wants (it's almost like the matte anodized finish on the gold iPhones) ... but as soon as we put it though corrosion tests it failed. By the time they solved the corrosion resistance the matte finish is almost complete gone, with very bright undertone and some brush marks remaining.
Is there anything we have done wrong? Or is this a fool's errand?
Product development - Irvine, California
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A. Hi Harry. Although gold plating is extremely corrosion resistant, you are probably not applying it nearly heavy enough for corrosion resistance on its own. It's probably porous, and it was probably the nickel plating which was providing most of the corrosion resistance. Thus, while there are several good ways to get a "brushed finish", in trying to achieve it by just skipping the copper and nickel plating, you picked a bad way.
I wouldn't call it a "fool's errand", but it does sound like both you and your plating shop are vainly hoping the guy on the other side of the ocean has some experience in this :-)
You can use a Time-Saver (wide automatic belt sanding) to impart a brushed finish, or you can bead blast the parts. Or possibly you can apply a dull nickel plating, and a dull gold plating. My bet is that time-saving, followed by conventional nickel plating, followed by a duller gold plating will give the look you want without significantly compromising corrosion resistance.
Ted Mooney, P.E. RET
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finishing.com - Pine Beach, New Jersey