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I have an original Commodore PET from 1977, that I have recently electrically restored, but there are some rust spots on the case.

rust spots on Commodore PET

It seems that I should at least do something to inhibit further rusting, and maybe even repaint it. If I repaint, I'm guessing it should be automotive paint, but don't have much clue beyond that. I'd like to match both color and texture, and I'm not sure how to deal with the black logo sticker. It doesn't appear to be simple to remove without destruction.

I'm seeking competent advice on how to:

  1. remove the rust (my inclination is rubbing compound and then sandpaper)
  2. find the appropriate matching paint
  3. preserve the front sticker while addressing the rust under it
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    I've seen all sorts of techniques for removing rust. Some are pretty weird like using cheap cola and tinfoil.
    – cup
    Aug 9 at 13:51
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Preface, I assume you already checked related questions like:

before posting, right?


It seems that I should at least do something to inhibit further rusting, and maybe even repaint it.

Commercially available rust converters are the best way to reduce existing spots and prevent further rust.

Besides, a worthwhile paint job isn't just adding paint 'paint', but several steps of filler, smoothing and painting, all in line with the original paint finish. The extreme poor quality of Commodore's original painting gives even a specialist a hard time to just fix it up. The only (somewhat) promising way is to completely strip all existing paint (and rust) using chemical paint remover and repaint it in a similar manner as the first time.

Do not use sand blasting, not even dry ice based, as it will change the surface structure and require filler and a completely different painting technique compared to the original one, resulting in a different appearance. Same goes for sand paper treatment.

I've seen many 'restored' PETs that came out worse than before. At best they are visibly different. I'd strongly advise against repainting. Not just because it's a complex task if done right, but it destroys the history of that machine. Every scratch and every rust spot tells a story about the machine's history. So if your intent is to preserve a classic computer and its historical significance, then a museum quality treatment is way more appropriate. For a PET case this means:

  • Cleaning it up
  • Applying rust converter
  • Add a hard wax cover

and enjoy/present it as the piece of history it is.

Of course, if your goal is some soulless shiny bling bling, then go with:

  • Chemical paint remover
  • Rust converter
  • Smooth sanding with very fine sand paper (block applied)
  • Professional painting by a car paint shop
  • Or, as an even more durable (and shiny) alternative: Powder Coating.

Have the painting/coating done by a professional shop (they may as well do the previous steps) to get a worthwhile result.

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    "if your goal is soulless shiney bling bling" :D
    – Edward
    Aug 9 at 14:29
  • Thanks for the links. Yes, I've read those and also tried to find out what professional restorers do: computerhistory.org/blog/… I also looked for restoration advice from the Deutches Museum in Munich which has a nice computer collection, but didn't find anything there. A canonical "How does a museum restore a computer?" might be helpful.
    – Edward
    Aug 9 at 15:12
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    The principle is similar to restoring a historic building: in extreme cases, partial replacement may be appropriate, but in that case, the repair should be localised and obviously non-original. Aug 9 at 20:32
  • @TobySpeight: As an example of obviously non-original in a building: xenomorphs in a cathedral elnortedecastilla.es/palencia/201502/21/…
    – ninjalj
    Aug 9 at 23:32
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Don't even think of using sandpaper. Even very high grain will mar the surface and the surrounding paint.

Repainting is such an enormous job to do right, that you shouldn't even attempt it, if you have to ask how and if. Especially not on something as precious and irreplaceable as this.

Use vinegar and a gentle brush to remove the rust. Wash throughly to remove all traces of vinegar afterwards. If there is some especially hard spots, don't just brush like crazy on that place. The surrounding finish will get damaged. Use the corner of an old credit card or something of similar hardness to scrape the tough spot.

If you feel the need to cover the de-rusted spots use paint that is easily removed. I'd use paint that doesn't necessarily match to proudly display the history and restoration of the machine. Take a leaf from this: https://en.wikipedia.org/wiki/Kintsugi

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