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Corrosion of stainless steel tank

We have a stainless steel water bath for patient and we store water for weeks by adding chorine to maintain ph and chlorine level and monitor by test tablets or powder. At present we noticed some traces of rust on the bottom surface of the tank.We want to know what could be the reason--either iron oxide in water or quality of steel.

Francisco Fernandes
- Kuwait

Chlorine dissolved in water will produce some hydrochloric acid. This will interfere with the passivity of the stainless steel allowing it to rust like carbon steel. Drain the tank and remove the rust. To do this you may use a citric acid [on eBay or Amazon] preparation. Rinse it well preferably with deionized water and fill it with deionized water containing 1/2 weight % of hydrogen peroxide 3%) [affil links], leave overnight and drain. Refill as usual. Don't chlorinate it any more but use a peroxide based sanitizer at concentrations recommended for the water end use.

Trevor Tipton
- Singapore

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