Remove rust stains from sinks using lemon juice and salt paste applied directly to the stain. Let it sit 30 minutes then scrub with a soft brush. Bar Keepers Friend powder mixed with water creates an effective paste for stubborn rust. For porcelain sinks a pumice stone gently buffs away discoloration. Avoid abrasive cleaners on stainless steel. Commercial rust removers with oxalic acid work quickly. Identify and fix the rust source such as iron-rich water or corroding hardware.