Oxalic or Phophoric Acid for Bathtub

Hi,
My bathtub is cast iron and 62 years old. The previous owner was elderly and wasn't able to clean very well. It has quite a bit of calcium, lime, soap scum and rust deposits. From reading this group and various other sources I know I need to clean it with acid I'm just not sure which would be better - phophoric or oxalic acid (aka wood bleach). I know oxalic is poisonous and phosphoric is little easier to deal with but I want the best results possible. Refinishers do an acid cleaning before they refinish a tub. Anyone know what they use? I would appreciate any info you may have regarding acid use for cleaning a tub with these kinds of stains.
Also, after cleaning does it make any sense to use a polishing compound to buff out the tub? I'd like to restore whatever luster or life it has left in it and I don't want to resurface. I was thinking of a buffing compound such as what is used on cars after they are newly painted. I believe this has a componenet similar to a very very fine grit wet/dry sand paper. Aren't tub paints similar to what are or used to be used on cars?
Any thoughts would be greatly appreciated.
Please e-mail direct to snipped-for-privacy@sbcglobal.net
Thanks very much.
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Hi Jen
Muriatic Acid 50% solution or 15 degree baume (store bought is usually 30 degree baume so cut it in half with water) But NOTE: This will also etch the porcelain a little.
Refinishers use Sulphuric Acid to clean ceramics before refinishing. Not something you want to mess with.
TTUL Gary
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I agree--I learned that from my plumber father!!
Sijka

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