Resurected this thread so I can update. I couldn't get the lime of with soft chemicals (I'm not going into how I stank up the garage with 5 litres of vinegar
) so I went with an angle grinder and sanded the surface. One might say I ruined the original color, but considering I found enough rust underneath for two my cars and believe there was not much to ruin.
Then I took some hydrochloric acid and gave it a gentle wash. This is what came out
I'll put an anti-corrosive layer on it and spray it with a model paint. Now, which color did the Kriegsmarine use
