Rust stains on kitchen knives (and other cutlery) are often the result of fly rust and/or pitting.Knives with harder steel have a higher carbon content and are therefore more sensitive to rust. A knife with harder steel is a very good knife and is therefore chosen for its better cutting properties and because it stays sharp longer. When choosing a knife made of harder steel, the knife's susceptibility to rust must be admitted.
Dishwasher rust:
1: Fly rust: Within a wash, other kitchen accessories are often washed as well. Objects that are less rust-resistant show rust, which can come off. These rust particles end up on other accessories such as the kitchen knives. However, food residues and other materials flying around in the dishwasher can also cause a reaction, which can be rust. However, this can all be removed with a scouring sponge. So, fly rust is not caused by a lower quality steel of the affected (possibly rust-free) object itself; the source of the rust particles is external.
2: Aggressive dishwasher detergents: If you (accidentally) put the accessory in the dishwasher, pit corrosion can occur. Pit corrosion is caused by the combination of temperature, salt from the dishwasher tablet, water (of course) and the aluminum in the dishwasher. You only have to throw one aluminum accessory next to the kitchen knife in the dishwasher and these four factors create a situation where rust has free rein.
3: Moisture spots: When a food tool is left in the dishwasher for too long (for example, after a wash), there is a greater chance of moisture spots forming.
The risk of rust can be reduced if the following rules are observed:
- After using the knives, clean them immediately with handwash and dry them immediately.
- Never put the knives in the dishwasher. The combination of salts, moisture and heat has a negative effect on the rusting process.
- Never leave your knives in a damp environment such as a sink or washing rack.
- Sharpen your knives from time to time. This keeps rust on the cutting edge as low as possible.
Light rust can be removed in various ways. Depending on the nature of the rust and how deep it’s in the steel, you can start by washing the knife thoroughly under the hot tap. You can also use a sponge, but be careful with the sanding side to avoid scratches. If this still does not work, it is also possible to use a light polishing agent, for example a polishing cloth in combination with a polishing agent. Please note that polishes carry a risk. It can change the finish of a blade, causing dull spots.
Definitions:
Stainless steel (ss): Rustproof or stainless steel, also called inox, is an umbrella term for a number of alloys of mainly iron, chromium, nickel and carbon. At least 11 to 12% chromium and a maximum of 1.2% carbon are required to be able to speak of stainless steel. Many types of stainless steel also contain the elements molybdenum, titanium, manganese, nitrogen and silicon.
Pit corrosion: Pit corrosion is a form of corrosion in which pits are formed in the surface. This "disturbance" of the surface can cause rust to form there.
Fly rust: Fly rust (surface rust) consists of small rust particles brought in from the environment. Stainless steel cutlery can also be attacked by rust particles from other objects in the dishwasher. Because of the necessary hardness, knives as a rule have a slightly less noble alloy than spoons and forks. That is why knives can be more susceptible than other cutlery to corrosion by rust particles pumped around in the dishwasher.