Brabantia kitchen knives can rust when the chromium oxide layer of your knife is damaged. The chromium oxide layer recovers by itself. But when your kitchen knife comes into contact with even the smallest drop of water before the chromium oxide layer is repaired, rust or pit corrosion will occur.
Damage is caused by bumps, dishwashing detergent, cleaning products, juices and acids etc. You can often remove the rust yourself. Just brush away the rust with a soft cleaning cloth and a special stainless steel maintenance product. Or pour a splash of vinegar on a soft sponge, and rub away the rust stains.