While working with some rust converter (MSDS, ~20% phosphoric acid by weight), a sequence of events that would make Rube Goldberg proud led to me spilling about 500mL of it all over the place. Yes I was wearing gloves and an acid gas respirator.

I'm not really well versed in chemical cleanup procedures and I needed to act fast so I kind of winged it by:

  1. Wiping the majority with a bath towel.
  2. There happened to be a box of baking soda right there so I dumped a bunch of it on the remaining spill.
  3. It fizzed for a bit then I wiped that up.
  4. I shop-vac'd the rest of the baking soda.

My question is just: Did I handle that OK? And, if not, how should I be prepared if that happens again? (I've been working with the chemical a lot lately.)

The reason I ask is, when I took off my respirator, it still smells like rust converter.

Also, it just happened so I won't be able to see any effects for a few hours but I'm hoping I don't start seeing rust spots on the metals it contacted, or dried crystals, or tear up any of the finish on the wood it contacted. But I'm hoping I got it.

Also, there are cats here and I don't really want residue to be left laying around.

So I'm wondering if that was a decent reaction, or if it was dangerous (I dunno what phosphoric acid + baking soda produces, although the space was well ventilated); and if it was effective, or if there is a better way.

Context is home shop, primarily woodworking; not a lab. So I don't have those nice metal lab tables or anything; lots of cracks, crevices, porous surfaces (concrete and wood), and stuff. And while I normally work with this stuff on a tray for small splash containment, this was a rather... violent spill (heh).

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    $\begingroup$ Don't panic. Phosphoric acid is one of the components of Coca-Cola, so it is not poisonous by itself. Avoiding contact to high concentrations should keep you save. $\endgroup$ Commented Jan 9, 2021 at 15:21
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    $\begingroup$ You did well. I'd add a solution of baking soda, just to chase the last traces of acid in all those cracks and crevices. On a side note, phosphoric acid by itself does not smell. $\endgroup$ Commented Jan 9, 2021 at 15:45
  • $\begingroup$ @ivan Ah must be something else. I think it's the smell after it reacts with iron because it's definitely common to rust remover and converter products. It's sort of like metallic fruit. I find it nauseating. $\endgroup$
    – Jason C
    Commented Jan 9, 2021 at 18:05

1 Answer 1


The product you were using is very likely a "rust converter". Used to convert rust to a stable products before painting . I have used it several times , usually I just rinse the surface , let it dry and paint . It is also used for industrial maintenance coating of poorly prepared surfaces ( those not sand blasted). That is ;it is commonly used and when I worked with coatings I never heard of a problem. Baking soda will neutralize it . I once inspected super phos storage tanks : it starts as 107 % phosphoric acid used to blend liquid fertilizers. When I stepped out of the tank and walked across the limestone gravel ,each step of the rubber boots left some jelly-like acid which foamed on the gravel. The people that worked at the facility thought nothing of it; from that I conclude neutralized phos acid it not a problem . Sorry this is all anecdotal ,but I have never needed to research the situation.

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    $\begingroup$ "It is also used for industrial maintenance coating of poorly prepared surfaces ( those not sand blasted). " ... my dentist uses it, too, thankfully not sandblasting my teeth. $\endgroup$ Commented Jan 9, 2021 at 18:29

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