Factors Contributing to Stainless Steel Pipes Rusting

Why Does Stainless Steel Pipes Rust?

When brown rust spots appear on the surface of stainless steel pipes, people are often surprised. The common belief is that "stainless steel doesn't rust, so if it does, it can't be stainless steel—there must be an issue with the material." This is a misconception stemming from a lack of understanding about stainless steel. Under certain conditions, stainless steel can indeed rust.

Stainless steel has the ability to resist atmospheric oxidation, known as "stainlessness," and also has the ability to resist corrosion in media containing acids, alkalis, and salts, known as "corrosion resistance." However, the extent of its corrosion resistance depends on the chemical composition of the steel, the processing state, the conditions of use, and the type of environmental medium. For example, 304 stainless steel pipes have excellent anti-rust capabilities in a dry and clean atmosphere, but if moved to a coastal area with salty sea mist, they will rust quickly. In contrast, 316 stainless steel pipes perform better in such conditions. Therefore, not all stainless steels are corrosion-resistant and rust-free in every environment.

Common Causes of Stainless Steel Pipes Rust

Stainless steel relies on a very thin, yet tough and stable chromium-rich oxide film on its surface to prevent further oxidation and rusting. If this protective film is damaged, oxygen from the air or liquids can penetrate and cause the iron atoms in the metal to continuously oxidize, leading to rust formation. The common forms of damage to this surface film in daily life include:

Electrochemical Corrosion: Dust containing other metal elements or particles of different metals can accumulate on the stainless steel surface. In humid air, the condensation water between the attachments and stainless steel can form a micro-battery, leading to an electrochemical reaction that damages the protective film.

Organic Substance Corrosion: Organic liquids such as vegetable or noodle soups, and even sputum, can adhere to the stainless steel surface. In the presence of water and oxygen, these organic substances can decompose into acids, which corrode the metal surface over time.

Chemical Substance Corrosion: Substances containing acids, alkalis, or salts (like alkaline water or lime splashes from wall decorations) can stick to the stainless steel surface, causing localized corrosion.

Polluted Air Corrosion: In environments with polluted air containing large amounts of sulfides, carbon oxides, and nitrogen oxides, condensation can form sulfuric, nitric, or acetic acid points, leading to chemical corrosion.

Tips for Preventing Stainless Steel Pipes Rust

To ensure the stainless steel surface remains bright and rust-free, we recommend the following:

Regular Cleaning: Frequently clean and wipe the stainless steel surfaces to remove attachments and eliminate external factors that can cause rust.

Use Appropriate Material in Coastal Areas: In coastal regions, use 316 stainless steel, as it is more resistant to seawater corrosion.

Choose Reputable Manufacturers: Some stainless steel pipes on the market do not meet the national standards for their chemical composition and fail to achieve the 304 material requirements. Users should carefully choose products from reputable manufacturers to avoid rust issues.