The tenants at my daughter's rental property let the bathtub faucet drip for a couple of years, building up a rusty area about 12 inches in diameter beneath the faucet, except directly under the drip where the build-up was washed away. I tried a spray-on iron/rust remover, but it only helped around the edges. I was able to scrape off a little portion using a screwdriver, but am scared that I may damage the tub. Can anyone recommend a super- strength remover? I vaguely remember something about oxalic acid as being useful, but not sure.
TIA,
Bob Hofmann