Why doesn't stainless steel rust？

The anti rust essence of stainless steel is the formation of a self-healing passivation film with high chromium content, supplemented by elements such as nickel and molybdenum to enhance comprehensive performance. However, its "non rusting" characteristics need to meet the requirements of composition and environment

What are the main factors affecting stainless steel corrosion?

The content of alloying elements. The smelting process of production enterprises can also affect the corrosion resistance of stainless steel. The external environment, with a dry and well ventilated climate, is less prone to rusting.

 

Corrosion-Prone Scenarios for Different Types of Stainless Steel

Stainless Steel Type	Corrosion-Prone Scenarios	Reasons
304 Stainless Steel	- Seawater, chloride (Cl⁻)-containing solutions - Uncleaned welded joints - Strong acidic/alkaline environments	- Lack of molybdenum (Mo), limited Cl⁻ resistance; - Sensitization leads to chromium carbide (Cr₂₃C₆) precipitation, causing intergranular corrosion.
430 Stainless Steel	- Humid atmosphere - Weak acidic solutions (e.g., dilute acetic acid)	- Ferritic structure with lower chromium content (16–18%); - No nickel to assist passivation, resulting in less stable passive film.
410 Stainless Steel	- Saltwater - Acidic sweat (e.g., knives in long-term contact with skin)	- Martensitic structure with only 11–13% chromium; - Poor corrosion resistance due to lower alloy content.
200 Series Stainless Steel	- Long-term humid environments - Low-quality decorative parts (e.g., low-nickel stainless steel with high manganese content)	- Manganese substitutes for nickel, reducing passive film stability; - Reacts with sulfur and chlorine in humid conditions to form rust.

 

How to deal with rust spots on stainless steel?

chemical method
Use acid pickling paste or spray to assist in the re passivation of corroded areas, forming a chromium oxide film to restore their corrosion resistance
Mechanical methods
Sandblasting cleaning, using glass or ceramic particles for shot blasting, annihilation, brushing, and polishing

 

What would cause stainless steel to rust?

Although stainless steel is known for its extremely corrosion-resistant properties, it is prone to rusting in certain situations. Although rusted metal is usually the result of exposure to water, stainless steel can also rust due to exposure to harmful chemicals, salt water, grease, or prolonged exposure to high temperatures

 

How do you keep stainless steel from rusting?

Stainless steel is less prone to rusting in environments with less corrosive media and mild environmental conditions. Its corrosion resistance mainly depends on the compatibility between the alloy composition of the material itself (such as chromium, nickel, molybdenum content) and the environment