Oxidation stains or rust can cause serious illness if consumed. Rust forms on the surface of iron or steel exposed to water and air for a length of time, including the blades of knives. Kitchen knives left sitting in the sink, or hunting and ornamental knives slipped into sheaths with moisture on their surfaces, have a high chance of rusting. Remove oxidation stains on a knife blade as soon as you notice it to stop rust damage and reduce the risk of accidentally cutting food with a rusty knife.
Coat the knife blade in metal cleaner or a penetrating lubricant such as WD-40. Cover the entire blade of the knife.
Lay the knife on a clean rag. Allow the cleaner or lubricant to soak on the knife's blade for one or two hours.
Wipe off the surface of the knife. Starting at the base of the blade near the hilt, slowly rub a soft cotton cloth or chamois along one face of the knife blade. Repeat until that face is clean, then switch to the other side of the knife blade. Avoid changing the direction of the stroke to reduce the risk of accidentally cutting yourself.
Rinse the blade under water to remove any remnants of the cleaning agent. Pat the knife dry afterward.
Apply more cleaner or lubricant if oxidation stains remain. Allow the cleaning agent to sit for another one or two hours, then repeat the process.