Summary for brownish gold finish Discussion
brownish gold finish on glove box latch is discussed as likely a plated or coated zinc part rather than a unique mystery finish. Lew Bisbing asked whether the latch’s brownish-gold appearance was a conversion coat over cadmium or zinc, noting he had not seen it elsewhere on the car. Marc Banks suggested it could resemble an rubbed oil finish, but thought paint was more likely for such an application. In a later reply, the finish was identified as probably a zinc die casting with a yellow/gold chromate conversion coating, likely hexavalent chromate in the original era, with trivalent chromate suggested for modern work. The responder also noted the part’s unusual shininess and said it may have been clearcoated either originally or during a prior restoration. The discussion leaves room for Marc’s paint theory, but the strongest practical guess is a chromated zinc die-cast latch.
April 24, 2013
Q. While restoring an old car I came across a brownish gold finish on the glove box latch. It appears to be a conversion coat over CAD or zinc but I can’t say I’ve ever run across this in the past, or anywhere else on the car. I’ve attached a couple photos in the event someone can identify the finish correctly.
Appreciate the help,
Lew
Lew Bisbing
Plating Hobby – Mesa, Arizona, USA
A. Lew,
I’ve had similar results to that finish using an rubbed oil finish, but considering the application I think it’s more likely to be a paint.
Marc Banks
Blacksmith – Boone, North Carolina, USA
A. Hi Lew. My bet is that the component is a zinc die casting and that it has received a yellow/gold colored chromate conversion coating. In those days it would have been a hexavalent chromate. These days you’ll want to go to a trivalent chromate conversion coating.
I find the shininess of this old part a bit surprising; it may be that either originally or as part of a previous restoration, it may have been sprayed with a clearcoat. Just my guess — not to say that Marc is wrong with his guess about it being paint.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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April 29, 2013
April 29, 2013
Thanks for helping.
Q. I have trivalent yellow, clear, blue and black — even know there is an OD available. Is it possible there may have been a hexavalent brown color years ago?
Don’t believe it’s paint, and considering the application, paint would chip off too easily.
Lew Bisbing
– Mesa, Arizona
May 1, 2013
Q. Mr Mooney, I’ve been thinking about what you said, believing the part may be “zinc cast”. So between the textured surface finish and no brighteners, once cleaned, if the part were dipped into a yellow chromate do you believe the bronze finish can be achieved?
What comes to mind is aviation high strength bolts that get plated less brighteners due to hydrogen embrittlement concerns, they tend to look more gold, but the finish and starting material is much better.
I may try doing this over the weekend.
Lew Bisbing
– Mesa, Arizona, USA
May 5, 2013
Q. I tried a portion on the latch with yellow trivalent chromate, not even close . . . .
I have to believe there must have been a bronze hexavalent chromate used, but have not gotten a solid confirmation from the restoration sites either.
Lew Bisbing
– Mesa, Arizona, USA
A. It almost appears to be cadmium with an olive drab over it. It’s hard to tell as I’ve only seen CAD with olive drab once. We had a plater ask us to olive drab some parts that they had plated.
Jose Bustamante
– Oshkosh, Wisconsin, USA