On Fri, 22 Feb 2013 18:29:54 -0800, Oren wrote:

The table is plastic. Easy
The concrete just etched. Porous
No?

Yes. The concrete turned whitish where the phosphoric acid landed
after dripping off the table.

While pool acid is not recommended for hand tools (it pickles them
but apparently makes the result MORE susceptible to rusting), it seems
to work wonderfully for plastic tables.

Tomorrow I will experiment with the following on that rust and on
the lime of my shower stall.

1. Vinegar (aka ketchup)
2. LimeAway (sulfamic acid)
3. Lemon juice (citric acid)
4. Coca cola (weak phosphoric acid)
5. Naval Jelly (strong phosphoric acid)
6. We already know muriatic acid works fantastically on table rust!