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.