Why is stainless steel not easy to rust?

"Rust" refers to the discoloration or corrosion caused by the chemical interaction between the surface of steel and the oxygen, moisture, acid, alkali, salt and other substances in the atmosphere, and the substance "rust" produced on the surface

Stainless steel means steel that is not easy to rust, and "stainless" here is relatively speaking. There is no metal in the world that does not rust. Even gold will rust in aqua regia. Why is stainless steel not easy to rust? This is actually related to the metallic element chromium. Chromium can quickly form a dense passivation film on the surface of the steel. The passivation film can greatly enhance the corrosion resistance of the steel. People have done such an experiment: two pieces of stainless steel and ordinary carbon steel with a mass of 20 grams were boiled in dilute nitric acid for a whole day and night. As a result, ordinary carbon steel was strongly corroded, but stainless steel was basically not corroded.

Because stainless steel is not easy to rust, many corrosion-resistant equipment in chemical plants are made of stainless steel. For example, in a synthetic ammonia plant, more than twenty kinds of stainless steel with different properties are needed.

In family life, the main reason to prevent stainless steel from rust is not to damage the passive film on the surface of the stainless steel. Stainless steel items should be cleaned as soon as possible after use, and try not to contact acid and alkali items.