The reason stainless steel is "stainless" lies at its core in its excellent corrosion resistance. Gaining a deeper understanding of the factors affecting corrosion resistance helps us better leverage the material's performance advantages in practical use.

1. The Passivation Principle of Stainless Steel

The corrosion resistance of stainless steel primarily comes from the dense chromium oxide passivation film formed on its surface. When the chromium content exceeds 10.5%, this protective film, only a few nanometers thick, spontaneously forms on the material surface. This passivation film effectively blocks further attack by oxygen and corrosive media, and even if the surface is scratched, it can self-repair in an oxygen-containing environment.

2. Common Types of Corrosion

Stainless steel may face various forms of corrosion in practical use: pitting corrosion, which is localized corrosion pits generated in specific corrosive media, with chloride ions being the most common cause; intergranular corrosion, mainly occurring in the weld heat-affected zone; stress corrosion cracking, occurring under the combined action of tensile stress and specific media; crevice corrosion, occurring in structural crevices or under deposits. Understanding the causes of these corrosion types is the foundation for taking targeted protective measures.

3. Influence of Alloying Elements on Corrosion Resistance

Chromium is the core element determining the corrosion resistance of stainless steel. Molybdenum significantly enhances pitting and crevice corrosion resistance. Nickel primarily improves resistance to reducing media corrosion while stabilizing the austenitic structure. Nitrogen both increases strength and improves pitting resistance. Different grades adjust alloying element ratios to adapt to different corrosive environments.

4. Usage and Maintenance Recommendations

Even stainless steel requires proper maintenance. It is recommended to regularly clean the surface to remove dust and contaminants; avoid prolonged contact with carbon steel and other dissimilar metals to prevent galvanic corrosion; in highly corrosive environments such as coastal areas, select 316L or higher-grade materials.