Copper chassis ?

[DaveWell]

interesting exploitation...

https://www.youtube.com/watch?v=5WIKKXdxNH8

[rooster]

Fender tweed chassis on the exterior were chrome plated just like the car bumpers of the day: chrome plating over copper over steel. The interiors were not plated with chrome but something else, something that could be soldered to. Was this interior tin plated? Maybe, but whatever it was it could be soldered to.

[martin manning]

I think it is unlikely that the original tweed chassis were plated with different metals on the inside. The difference in appearance is due to the amount of polishing done before plating, which for economy would have been limited to the exposed face. Most automotive "triple" chrome included a layer of copper followed by a layer of nickel, and finally a layer of chromium, which is interesting from a conductivity point of view.

[R.G.]

The multiple layers of metal in chrome plating is a consequence of the electrochemistry of the metals. I don't recall all the details, but chrome isn't compatible for plating directly onto steel. Copper is, so the copper is plated as a "primer coat" that will stick to the steel. Copper will form a long-lasting bond to steel. But again, not chrome. Nickel will stick to copper AND chrome, so the next layer is nickel, and finally chrome.

The exact details are fuzzy to me, as it's been a couple of decades since I last looked at this.