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Zinc plating for auto part restoration

Posted by garyd

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Zinc plating for auto part restoration #1
garyd Gary Dabrowski Naugatuck, western Connecticut, USA 1974 MG MGB 1975 MG MGB	Posted: June 20, 2012 03:15PM Registered: 3 years ago Posts: 613

Time to “remanufacture” or replace my brake and clutch master cylinders as a part of a complete pedal box restoration. One option is to purchase remanufactured master cylinders, the other is to re-plate the originals after honing the bores in preparation to receive the rebuild kits. As I prefer to lean more towards period correct solutions and to re-use the major original parts where appropriate, I would tend to rebuild and re-plate.

The question here is this. Does anyone have any experience with platers that can apply the correct zinc finish on these parts and has auto part restoration experience? Can anyone make a recommendation? Along the same lines, what is the correct technical description for the plating? There as quite a few zinc chromate processes out there.

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Re: Zinc plating for auto part restoration #2
Dave Braun Minnesota, USA 1952 MG TD "Tommy" 1970 MG MGB "Maggie" 1974 Triumph Spitfire 1500 "Sammy"	Posted: June 20, 2012 04:33PM Registered: 1 year ago Posts: 2,005

Gary,

Eastwood has some good finishes that spray on and replicate the zinc plating look. If you go that route, I would consider silicone fluid as it won't harm that finish.

The term is electroplating, and it isn't uncommon, especially for zinc. I do some at home on smaller objects and use a chromate finish to replicate the blue or yellow cad plating that industry uses. Look for a thread Adrian Paige had on the subject in November or December. Basically a anode of the desired material is placed in a solution with a positive connection to a power supply, and the part becomes the cathode with a negative supply.

In my experince zinc chromate refers to the paint used with a heavy zinc concentration to preserve aluminum prior to finish coating. Aircraft from the 70s on are commonly light to dark green inside due to the zinc chromate paint.

That said, I leave the cylinders natural. I don't want to get any plating inside them. At the most spray them with a clear enamel is what I would do.

Warmly,
dave

Edited 1 time(s). Last edit at 06/20/2012 04:34PM by Dave Braun.

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Re: Zinc plating for auto part restoration #3
garyd Gary Dabrowski Naugatuck, western Connecticut, USA 1974 MG MGB 1975 MG MGB	Posted: June 21, 2012 08:27AM Registered: 3 years ago Posts: 613

Thanks Dave;

Would be nice to know for sure if the factory applied a plated zinc or cadmium protective finish to the brake and clutch master cylinders or if they were simply coated with a preservative that eventually wore off leaving the iron to create a "patina". If the latter, I agree that it would certainly be easy to restore/refinish the parts surface given the Eastwood products now available.

This rolling restoration is not intended to be 100 percent perfect as I shall make updates to systems for safety and functional reasons especially where such changes are not readily apparent. In this case, having an appropriate plated finish applied is not a problem as I have the resources to do it.

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Re: Zinc plating for auto part restoration #4
Dave Braun Minnesota, USA 1952 MG TD "Tommy" 1970 MG MGB "Maggie" 1974 Triumph Spitfire 1500 "Sammy"	Posted: June 21, 2012 10:33AM Registered: 1 year ago Posts: 2,005

Gary, then I'm going to go out on a limb and say the cylinder castings were cad plated before machining. That would be the route I would finish them to, if I wanted to go original. If you coat the inside of the cylinders with light grease, the bores should not take the plating, but that may contaminate the plating solution.

Here, cad plating for hobbiests is almost NLA. The yellow cad chromate from Caswell works good on freshly zinc plated items.

warmly,
dave

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Re: Zinc plating for auto part restoration #5
pinkyponk Adrian Page Nova Scotia Canada, Canada 1971 MG MGB GT 1973 MG MGB MkIII	Posted: June 21, 2012 10:42AM Registered: 2 years ago Posts: 2,745

Like this? I did this in chemicals from Caswell Plating. I lightly re-honed the cylinder after I plated it just to be sure it was OK. The gold/colours are from the yellow chromate dip process done after plating.

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Re: Zinc plating for auto part restoration #6
pinkyponk Adrian Page Nova Scotia Canada, Canada 1971 MG MGB GT 1973 MG MGB MkIII	Posted: June 21, 2012 10:45AM Registered: 2 years ago Posts: 2,745

Here is the link Dave referred to. http://www.mgexperience.net/phorum/read.php?1,1958070,1958070#msg-1958070

It will give you some idea of what's involved. I can't imagine not being able to do this now. It's a very useful process to anyone restoring a car.

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Re: Zinc plating for auto part restoration #7
garyd Gary Dabrowski Naugatuck, western Connecticut, USA 1974 MG MGB 1975 MG MGB	Posted: June 21, 2012 12:24PM Registered: 3 years ago Posts: 613

Looks real nice Adrian;

I'll dig up my copy of Clausager and see if I an find any photo evidence of plating on these things.

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Re: Zinc plating for auto part restoration #8
bcodegard38 Ben Odegard Livermore, CA, USA 1972 MG MGB	Posted: June 21, 2012 12:35PM Registered: 2 years ago Posts: 280

With very few if any exceptions, Cd is no longer used as a plating to prevent rust on steel fasteners. At moderate temperatures and low stresses, Cd can embrittle some steel alloys. The aircraft industry used Cd plated on low alloy, high strength bolts to attach jet engines to the wing structures. Scary to think about it. One engine did fall off over Chicago area several years ago. This failure was attributed to Cd plating. Cd is also toxic for the poor guys doing the plating. Zn is the favored plating for corrosion resistance. Of course for looks you can't beat Cr or Ni. That yellowish tone on the MC looks like nickel plating. Good Luck

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Re: Zinc plating for auto part restoration #9
garyd Gary Dabrowski Naugatuck, western Connecticut, USA 1974 MG MGB 1975 MG MGB	Posted: June 22, 2012 08:58AM Registered: 3 years ago Posts: 613

Good points Ben;

There are a few interesting houses on the web that do restoration zinc plating for car parts. http://www.yellowzincplating.com/ look like a good bet.

Looks like zinc plating followed by a yellow dichromate passivate is the way to go.

Now if we only knew wether the factory actually did this or if they used some other process.

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