Stains occur when minerals in your water leave their mark on your tub or sink. Rust is particularly difficult to remove, and the situation is further complicated when your tub is enamel-coated. Abrasive cleaners can help to remove the stain, but they increase the risk of damaging your enamel permanently. Because you do not want to scratch your enamel, time is your best defence against rust stains.
Mix equal parts white vinegar and water in a bowl.
Plug the tub and pour the vinegar and water solution so it covers the rust stains completely. If the stain is on the side of the tub, saturate a towel with the vinegar and water and place it over the stain.
Let the vinegar and water stand for at least 1 hour and check to see if the stain is still present. Depending on the age of the stain, it may take several soakings to remove the rust completely.
Rinse the tub well when the rust stain is completely removed and clean as usual.
Do not use steel wool or abrasive cleaners on enamel tubs because they can permanently scratch the tub. If you do not have white vinegar, you can also use lemon juice.