Plating for Cast Aluminum Parts Chrome or Nickel

'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

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.

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.

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.

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

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.

DIY metal plating kits are sold here:

Some is a lot easier than others, but you can even do real chrome at home.

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.)

"It is in most cases still essential to deposit a thin initial layer of copper from a cyanide colution onto both steel and zinc alloy diecastings for reasons already discussed, prior to their being acid copper plated. Alternatively, a thin initial nickel layer deposited from any standard bath is also quite satisfactory on ferrous substrates. In both cases, the thin initial layer is often called a 'strike plate'. (_Nickel and Chromium Plating_)

Punctuation is per the original -- in other words, this is a British book. In American parlance, this initial layer is called a "strike layer." If you Google [nickel "strike layer"] you'll see that nickel is used for the strike on many other metals as well, often under a copper leveling layer, which is then topped with nickel, and then chromium. But cyanide-based copper can also used for strike layers. The leveling layer is sometimes electroless, but more commonly it's copper plated from an acid bath, rather than a cyanide bath.

Top-quality chrome plating, therefore, actually is a four-layer process, even if the first two layers are different methods of plating copper. My limited understanding is that nickel is used for the flash more often than copper in high-volume operations. It's done that way where durability is important and they don't want to use excessively thick layers of plating.

-- Ed Huntress

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.

How difficult is the zinc plating, Don?

-- Ed Huntress

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.

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:

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.

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.

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.

Acid copper doesn't stick to steel but it does to a nickel flash.

Caswell offers an alkaline copper (no cyanide) that works well as a flash or strike layer.

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

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.