After use, wash table and kitchen knives under running water! If knives are left uncleaned for longer periods of time with saliferous or acidic leftovers on them, stains can develop.
All household knives with plastic handles can be washed in the dishwasher. Also here, rinsing is recommended. In addition, make sure that the dishwasher is opened momentarily after cleaning. The hot water vapor and water condensation can also be responsible for stains and corrosion on the blades (crevice corrosion).
Stains can occur when aggressive or too much detergent is used.
More information can be found in the following documents: