Cleaning steel shell

Would anyone have any advice on how to clean the bottom of this shell, I am trying to identify the shell but I can not read the markings due to the rust. All I have been able to tell so far is that it is a 105mm APFSDS round.

the case is stamped M148A1B1 and as I recall waw only used with one type of 105mm APFSDS.
Jason will probably be able to tell us more.

KROIL will remove the rust without damaging the steel.

Thank you very much for the advice about the KROIL, out of curiosity would it be a good idea to try to redo the faded markings or is that a cardinal sin?

If your looking to resell or trade it, it’s best to leave it the way it is. By the way, KROIL is the best penetrating oil made. 2nd best: Knock-Er-Loose by CRC. We tried them all at Coca-Cola and that what we found.

It’s a long time ago when I did chemistry…however, I recall that you can convert iron oxide (rust) back to more stable iron (ferric) phosphate with phosphoric acid:

Fe₂O₃ + 2H₃PO₄ yields 2FePO₄ + 3H₂O

Have used phosphoric acid, many years ago, as a; ‘Rust Killer.’ It ‘was’ available as a commercial product.
Read current Health and Safety regulations carefully before use.

  • Teratogenicity / Embryotoxicity: Not known to harm the unborn child.
  • Reproductive Toxicity: Not known to be a reproductive hazard.
  • Mutagenicity: Not known to be a mutagen.

Hope this might be helpful.


I will have to read into it when I get home, chemistry was always my favorite in school. I loved balancing equations.

And KROIL is not toxic.
Second best, as far as I am concerned, is BALLISTOL, also not toxic, but not quite as good on rust as KROIL.
Personally, I would hesitste to use anything either toxic or acidic on anything collectable and/or valuable…

Phosphoric Acid in not only corrosive, it’s conductive. Many times the automated guided vehicles which carried cases of Coca-Cola would get into traffic accidents. Soda pop was spilled into the printed circuit card cage and then the dried pop would form it’s own circuit traces between chips. This made the AGV’s really go nuts. The solution was to rinse off the PCB’s with hot water, dry with compressed air and then restart the AGV. Problem solved.

Short video showing the use of a commercial phosphoric acid based iron oxide (rust) conversion…iron oxide to; ‘more stable,’ ferric phosphate.