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The Metal Backplates Empty The Metal Backplates

Post  ian1954 Mon Feb 11, 2013 9:55 am

I have been through a few comments on this site re the metal backplates and their finish.

I am still confused and I have quite a few that I would like to clean up and restore.

At first I thought these were a brass or bronze finish but this ended in disaster (only tried on broken plates!). (Fill and level with solder, smooth, electrolytic flash copper coating followed by brass or bronze)

Firstly, what is the base metal of the plate?

It looks like Mazak (Pot metal).

Secondly, having seen some of the earlier plates in pristine condition (shiny silvery) - they look to be Zinc plated. This has been quoted by Mark, recently, as being Zinc Dichromate but as far as I can see - that would produce a yellow brassy finish.

Thirdly, the yellowish finish - that could be zinc dichromate but it could also be zinc plating followed by a dip in "yellow chromate". This makes the zinc plate last longer.

Does anyone know the definitive process?
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The Metal Backplates Empty Re: The Metal Backplates

Post  pkrankow Mon Feb 11, 2013 10:08 am

I know the process changed over the years. Very early versions do not have the coating, later versions do. I would not be surprised if the coating was changed over time as the process costs changed.

I know most of my back plates are a "harder" metal, is not iron or brass, and have a "yellow" or "brown" coating which chips relatively easily. I would assume it is a zinc or aluminum alloy that is well suited to die casting.

Phil

interesting read
http://en.wikipedia.org/wiki/Mazak_%28alloy%29
more interesting read
http://en.wikipedia.org/wiki/Chromate_conversion_coating
Phil
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Post  WingingIt74 Mon Feb 11, 2013 10:56 am

The coating kinda reminds me of the old Rochester carburetors.
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The Metal Backplates Empty Re: The Metal Backplates

Post  Mark Boesen Mon Feb 11, 2013 11:10 am

Hi Ian,
I don’t know about definitive, but here’s what I know/think I know: The first (’56) backplates were a ‘clear’ dichromate soon followed by the ‘yellow’ dichromate, if this was the result of different companies doing the plating during this time I’m not sure.
I had just emailed Mud about this as I’d seen a 'yellow' RR-1 with vent tubes and the later ventless bakeplate (c.1957) in 'clear' but, once they went to the ‘brass’ plating in ’58 there was no other plating.


Last edited by Mark Boesen on Mon Feb 11, 2013 11:20 am; edited 1 time in total
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The Metal Backplates Empty Re: The Metal Backplates

Post  ian1954 Mon Feb 11, 2013 11:20 am

WingingIt74 wrote:The coating kinda reminds me of the old Rochester carburetors.

http://www.caswellplating.com.au/store/store.php/products/yellow-chromate-concentrate---cadmium-look
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The Metal Backplates Empty Re: The Metal Backplates

Post  Mark Boesen Mon Feb 11, 2013 11:26 am

yep, thats where i get my dye for anodizing.
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The Metal Backplates Empty Re: The Metal Backplates

Post  ian1954 Mon Feb 11, 2013 11:31 am

Mark Boesen wrote:yep, thats where i get my dye for anodizing.

Now is the RR1 crankcase adonised and then dyed yellow or is that dipped in yellow chromate?
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Post  Mark Boesen Mon Feb 11, 2013 11:42 am

yep, the crankcase anodized and then dyed yellow.


Last edited by Mark Boesen on Tue Aug 13, 2013 2:49 pm; edited 1 time in total
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The Metal Backplates Empty Re: The Metal Backplates

Post  Mudhen Mon Feb 11, 2013 12:04 pm

.


Last edited by Mudhen on Mon Nov 15, 2021 8:57 am; edited 1 time in total
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The Metal Backplates Empty Re: The Metal Backplates

Post  Motra Mon Feb 11, 2013 1:29 pm

What years were the back plates made that didn't say "made in USA?" Mine is a darker kind of brownish color. I would assume that it's prior to the brass plating and has aged itself to that color.

The Metal Backplates DSCF0031_zps2d08c9fe
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The Metal Backplates Empty Re: The Metal Backplates

Post  Mark Boesen Mon Feb 11, 2013 2:12 pm

'58-'59 to '63-'64, a little Brasso metal polish would clean it up nice, looks like it might of came from a pt-19.
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The Metal Backplates Empty Re: The Metal Backplates

Post  ian1954 Mon Feb 11, 2013 2:39 pm

As usual, I will arm myself with chemicals and give all permutations a go. I have quite a few busted backplates to work on!
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The Metal Backplates Empty Re: The Metal Backplates

Post  looperdude Tue Aug 13, 2013 8:37 am

fine steel wool gets the backplates looking new again, i have 2 that look brand new.
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The Metal Backplates Empty Re: The Metal Backplates

Post  Mark Boesen Tue Aug 13, 2013 2:53 pm

i'd be careful on the early backplates, the coating is not very thick and the steel wool would likely remove some, BRASSO metal polish and a soft toothbrush works.
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The Metal Backplates Empty Re: The Metal Backplates

Post  ian1954 Tue Aug 13, 2013 4:04 pm

After a great deal of research and testing, I can say that the backplates are zinc plated. It is extremely thin - only microns - and is applied after the alloy has been treated with Zincate.

The finished plating is then treat with a passivate to protect the Zinc.

A silver finish with clear passivate and the yellow (which darkens (eventually) to a brassy finish) with yellow passivate.

After treating with zincate the backplates can be plated with nickel or brass - this does not give an original finish. It only comes with time.

This is one that was quite badly pitted and corroded. Here it is after plating and passivating.

The Metal Backplates Clear_10

I would not recommend anything too abrasive (including steel wool) to clean a backplate. When the finish has been penetrated the zinc will corrode badly. Not immediately but over time.

I would not delve further than brasso!
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Post  looperdude Tue Aug 13, 2013 5:24 pm

well then that just sucks, wish i would have known that before putting steel wool on 'em.
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The Metal Backplates Empty Re: The Metal Backplates

Post  pkrankow Tue Aug 13, 2013 7:17 pm

If you are gonna run them they still have YEARS of life in them even without the coating.

Phil
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Post  looperdude Wed Aug 14, 2013 8:14 am

yeah i guess thats all that matters.
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The Metal Backplates Empty Re: The Metal Backplates

Post  roddie Thu Aug 22, 2013 7:51 pm

There's an old saying... "Paint & Chrome... Don't get ya' Home"
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The Metal Backplates Empty Re: The Metal Backplates

Post  ian1954 Fri Aug 23, 2013 8:50 am

There's an old saying... "Paint & Chrome... Don't get ya' Home"
[

Agreed!


The Metal Backplates Ntp310

But where does it end?


The Metal Backplates Nobby_10
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The Metal Backplates Empty Re: The Metal Backplates

Post  roddie Mon Aug 26, 2013 9:28 pm

gotta love those "Brits"... check this out... I just LOVE this!!!!

Turn up your speakers!



Last edited by roddie on Mon Aug 26, 2013 9:30 pm; edited 1 time in total (Reason for editing : comment "turn up your speakers!")
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Post  bullit132 Mon Aug 26, 2013 10:38 pm

thats one cool rig Cool  
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