Plating brass over chrome

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curtis cutter
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Plating brass over chrome

Post by curtis cutter »

A friend and I are restoring a 1971 Mack fire engine and are in need of a "gold" bulldog for the front. Chrome units abound but gold color not so much.

Brass or "Gold" bulldogs were used on engines that were 100% Mack Truck constructed as opposed to chrome that was used on multiple manufacturer vehicles. Can a chrome one be plated over with brass?

Gregg
Gregg
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Rich_Carlstedt
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Re: Plating brass over chrome

Post by Rich_Carlstedt »

I think you want to take it to a plater and have him "strip" the Chrome and then do your brass coat.
It may be possible to plate brass directly, but I believe you will find that surface contamination on the Chrome will cause a poor coat.
The platers always want to strip for that reason

Rich
curtis cutter
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Re: Plating brass over chrome

Post by curtis cutter »

Rich_Carlstedt wrote: Sun Oct 21, 2018 9:59 pm I think you want to take it to a plater and have him "strip" the Chrome and then do your brass coat.
It may be possible to plate brass directly, but I believe you will find that surface contamination on the Chrome will cause a poor coat.
The platers always want to strip for that reason

Rich
Thanks Rich.
Gregg
Just let go of it, it will eventually unplug itself.
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10KPete
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Re: Plating brass over chrome

Post by 10KPete »

If I recall correctly, there wants to be a copper strike layer on before the brass...

Pete
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wlw-19958
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Re: Plating brass over chrome

Post by wlw-19958 »

Hi There,

I can't directly answer your question but I do know that Colt
would nickel plate gun parts before doing a gold plate. It
would make the gold shinier with less actual gold being plated
and thus, saving costs.

By all means, check with the plater before you do anything.

Good Luck!
-Blue Chips-
Webb
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Harold_V
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Re: Plating brass over chrome

Post by Harold_V »

Strange as it may appear, gold readily migrates towards base metals, but that is prevented by nickel plating. For that reason, it is common in industry to nickel plate electrical components that are gold finished. I'm not suggesting that that is the reason Colt plated first with nickel, but it certainly is a possibility.

H
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wlw-19958
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Re: Plating brass over chrome

Post by wlw-19958 »

Hi There,
Harold_V wrote: Mon Oct 22, 2018 3:04 am Strange as it may appear, gold readily migrates towards base metals, but that is prevented by nickel plating. For that reason, it is common in industry to nickel plate electrical components that are gold finished. I'm not suggesting that that is the reason Colt plated first with nickel, but it certainly is a possibility.
That's interesting. What exactly does it mean
"migrates towards base metals?" I don't fully
understand.

Good Luck!
-Blue Chips-
Webb
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Harold_V
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Re: Plating brass over chrome

Post by Harold_V »

The phenomenon is discussed in Hoke's book on refining. When gold is applied, or even placed in contact with silver, if is found to migrate. It literally diffuses in to the other element, eventually disappearing (as far as sight is concerned). It's still there, but has been absorbed. Gold plated copper based alloy pieces eventually appear to have lost all gold without the nickel barrier being applied. Keep in mind, the plated layer is only millionths of an inch in thickness. We're not talking about a lot of gold. That may or may not occur with gold on steel, but gold, unlike silver, will alloy with iron. I expect it would be a problem.

H
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10KPete
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Re: Plating brass over chrome

Post by 10KPete »

I'll come from a few years in the printed wiring board and 'puter electrical contact field. As he said, gold will dissolve in copper, slowly but surely.

So. the spec for board edge connections was 20 uin. min. of nickle on the copper, then the gold. Usually there was a thickness given for the gold but that was driven by the application. The toughest application, from a mechanical standpoint, were switch contacts or connector contacts and for those the gold was spec.ed at 5 % cobalt hardened gold.

Pete
Just tryin'
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