Plating for Cast Aluminum Parts Chrome or Nickel

I'm wondering what plating materials can be applied to polished cast aluminum parts, and how difficult the process would be, such as unobtainable
chemicals or other problems.
It dawned on me that I've seen chrome plated alternators and other aluminum dress-up parts for cars, but never really paid that much attention to them. I've seen many applications where a flash-thin chrome plating finish peels off, and thicker, apparently poorly done or poorly prepared plating that peels, forming razor-sharp cutting edges (on hand tools, BTW).
I have an old Dumore 1/3 HP universal electric motor (approx. 3.5" dia.) that has a lustrous-silver appearance, and I've been wondering what the plating might be. The plating is old, I suspect 1950s or maybe as old as the 1940s, and doesn't look like new or old chrome generally does, instead, it's slightly dull (like myself) with a greyish and yellowish cast to it. This finish hasn't been cleaned any time in recent years, which looks better, to me anyway.
There is an area where some of the plating has been ground away (probably to remove an engraving) where a sub-layer looks like copper.
The bare base metal looks like oxidized aluminum, and it's non magnetic, so I assume it's cast aluminum, based on the unusual shape (motor end bells with various features such as bearing bosses and small oil ports with reserviors). Unlike most other electrical gear, I didn't disassemble this to see what it's like inside (only beause it didn't appear to have been tampered with).
I don't have any desire to restore the plated part, I just thought it to be a bit unusual for aluminum to be plated on a utility tool-type part, when just polishing the aluminum would have provided a good appearance, at least while the motor was new. It appears to have been polished prior to plating, but plating generally outlasts paint or other coatings.
The plating may have been a "pride in our name" and/or a better quality than our competitors' products appearance-comparison issue, in that bright plating would appear to be a much better grade of finish than wrinkle paint, I suppose.
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WB
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'Sounds like nickel. That was a common final plating until the '50s, when they started putting flash chrome on top of it for everything.

It probably is. Copper was used for leveling, but also to get a better grip. A typical first-class chrome plating job on steel is, first, a very thin flash coating of nickel (it promotes adhesion); copper plating to level the surface; a regular nickel plating on top of that; and chrome plating, often quite thin, on top of the whole works.

Nickel was stylish and implied quality in those days.

You probably suppose right.
-- Ed Huntress
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The chrome plating process is done in three steps, after polishing. 1st, a copper plate. This can be done thin, or heavy and repeatedly to use as a filler to sand out defects on old or pitted parts. 2nd, a nickle plate for the color. Nickle is soft and easy to scratch, but this is was the final finish until sometime in the mid 30's. 3rd, chrome has been described as a "hard clear coat" over the nickle, giving a brighter and more durable finish. This is where the redundant phrase "triple plated" originates. This process can be applied to nearly anything, leather baby shoes, wax forms, etc, if care is taken to avoid high temps in the tank. I find that aluminum tends to peel after a few years outside or on an engine, so prefer to polish it.
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Was Nickle plating until after WW2. The 1940-42 cars were nickel plated on the shiny parts, and not chrome. the 42's all went to the military and were painted over the shiny parts.
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According to the Antique Automobile Club of America judging standards, Oldsmobile started using chrome plating in 1925, the rest followed suit in 1928. I have heard of chrome plating as early as 1848 for jewelry, but it had problems. My 39 and 40 Grahams have a lot of Stainless Steel trim and chromed white metal.
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Thanks again, Ed. Would you know whether nickel is significantly less dangerous, easier or cheaper to apply to small parts on a hobby-level scale?
I kinda suspect that both would involve about the same aspects and safety issues.
The only source of nickel I know of presently, would be rods for electric welding cast iron, but I'm sure there would be sources of the right alloy to use for plating.
I think it's DoN that regularly applies electroplating to some of his small machined parts, so maybe there will be other comments regarding home shop plating.
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Not from personal experience, but it's supposed to be easy. So is copper. Some people here may have experience with the Caswell kits, which are very simple and apparently very satisfactory for many things.

Probably. Several people here have discussed it in the past.
-- Ed Huntress
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DIY metal plating kits are sold here:
http://www.caswellplating.com /
Some is a lot easier than others, but you can even do real chrome at home.
--

Roger Shoaf

About the time I had mastered getting the toothpaste back in the tube, then
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Thanks Roger, I was having a difficult time remembering what the company name was.
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On Fri, 6 Mar 2009 23:36:15 -0500, "Wild_Bill"

Don, not DoN. I plate with zinc, tin, copper and nickle using materials from Caswell. There are two nickle processes, electrolytic and electroless. Once you get your parts absolutely clean, electroless nickle plating is about as hard as boiling an egg.
Plating onto zinc, "white metal" or aluminum requires special steps. It can be done but I don't do it. Caswell does offer materials to do this, as in plating die-cast white-metal auto trim parts with chrome or nickel.
Caswell also offers chrome, but I don't mess with that either. Chromic acid is nasty stuff that produces toxic fumes, while the chemicals I use are quite benign.
www.caswellplating.com
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wrote:

How difficult is the zinc plating, Don?
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On Sat, 7 Mar 2009 13:26:53 -0500, "Ed Huntress"

It's very easy and un-fussy. I think it's almost easier than painting for small objects and projects. The work must be clean and if you want bright zinc then you need to add a few ml of brightener if the bath hasn't been used for a while. My zinc juice is in a covered 5-gallon bucket and it has been in use for several years. Figure about 30 mA per square inch of workpiece. Zinc throws quite well so orientation in the bucket isn't at all critical.
I often chromate the zinc because it's easy (just a dip) and it significantly enhances resistance to mild acids like fingerprints and acid rain.
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wrote:

Well, that sounds like it's worth looking into. Somebody once gave me the impression that it was tricky and much more difficult than nickel.
-- Ed Huntress
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Thanks, Don.. I realized my error when I noticed your remarks about their products as I was looking at the Caswell site today.
That is an easy website to find information on, almost as if they tried to make it easy for potential customers to find the correct products.
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Yep, we got the Don mistaken-identity-error (CRS) squared away DoN. Thanks again for the additional info. I could see the practical usefulness of tin and nickel, for a lot of items. I'm not too impressed by chrome, even if it was simple and easy.
As far as attractiveness of flashy or cool-looking appearances, colors in anodizing tend to be more impressive to me.
At the other end of the spectrum, I find black oxides, patinas and oxidation more attractive on lots of items. I think the rich, dark colors of dull-looking brass (dark brown) and copper (almost black) more attractive than highly polished and coated with a protective clear finish.
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    There is (or at least used to be) an "electroless nickel plating" solution offered for plating vias through printed circuit boards. (There was also an "electroless gold" for the same purpose.)
    O.K. A quick Google search for "electroless nickel" came up with a WikiPedia page which includes the following text:
=====================================================================It is also used extensively in the manufacture of hard disk drives, as a magnetically neutral base coating on aluminium platters (disks) prior to finishing with an magnetic read/write iron oxide coating. ====================================================================which suggests that it is a workable way for plating aluminum. The WikiPedia article is at:
    http://en.wikipedia.org/wiki/Electroless_nickel_plating
    The Google search found a lot of other hits, many of which are vendors of the solution for the purpose.

    Not I. Perhaps Don Foreman?
    Enjoy,         DoN.
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Most of the parts that I make that get plated are done in electroless nickel, as that's what was original for Lotus. I don't know who does the work, but can find out who our California source is if you want it.
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I sent machined aluminum microwave radio enclosures out for nickel plating because it was cheap and maintained conductivity between the cover and chassis better than the bare metal over time. These were prototype aircraft radios that may see condensation when descending into humid air. IIRC the lot charge was about $80 fifteen years ago.
I think nickel and copper plate well without cyanide, copper from the sulphate and nickel from the acetate, but I haven't tried it.
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Thanks for the additional info, Jim. It's mainly a curiousity to me at present, but plating small parts with nickel to inhibit corrosion and/or improve conductivity could be a very useful procedure if it's not too complicated.
I'll be having a closer look at Caswell's products and kits.
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On Fri, 06 Mar 2009 22:49:51 -0500, Wild_Bill wrote:

My understanding, from one of the mechanical engineers at one of my clients, is that copper is sort of the universal primer of metal plating -- it'll stick to most anything, and most anything will stick to it.
I'd never heard of a flash of nickel under the copper to plate steel, though.
(Note that one of the things this place buys is electro-formed shields -- the manufacturer makes an aluminum mandrel, puts a _thick_ copper plating on it, then chucks the whole thing into a solution that dissolves the mandrel but leaves the copper behind. It's a great way to make strong, light, thin-wall really complex pieces.)
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