I'm posting this here instead of the 140 board because there's more traffic here and it's a question applicable to 240s as well.

I'm restoring a '71 145 with the old Rallye cluster that came with the special (and now impossible to find) fuel sending unit. The car sat for a very long time with old gas that turned to varnish. The sending unit was literally encased in a thick hard gunk and rust debris. This is what it looked like:





I didn't want to risk picking at it or scrubbing it, for fear of breaking contacts or wire. Replacing is not an option as they are not replaceable, and so I figured I had nothing to lose by trying to clean it. I dissembled the sender and soaked it for several hours in this stuff: http://www.safestrustremover.com/

It's similar to evaporust - non abrasive, non-acidic, non-toxic, etc. It does an amazing job of removing the rust. But it also, however, removes the plating. Now it is totally cleaned up, all gunk and debris is removed and it looks like this:



I'm wondering what, if anything, I can do to protect the metal surfaces from rusting again that will be safe for inside the tank. I can't really get it re-plated due to the electrical components, and any further disassembly is too risky.

Does anyone have any ideas or suggestions on what I might try? Is there a fuel tank coating used to repair/refinish gas tanks that might work? I'll have to apply it by hand/brush.

I hope the sender still works, but I had to try.

Thanks.