Why Does Stainless Steel Rust?

Stainless steel is typically specified because of its ability to resist corrosion in a variety of environments. Unfortunately, stainless steel is not fully stain or rust-proof, it is just more resistant to corrosion that's why it's called "stain" "less" steel.

In the first place, why is stainless steel less likely to rust? to understand what makes stainless steel rust it is first important to understand the science that typically prevents it from rusting. 

chromium is the key element which makes it rust resistant. When the surface of normal steel is exposed to oxygen, it usually forms ferric oxide (Fe2O3) which has the well-known red rust color. When stainless steel is exposed to oxygen, chromium oxide is created on the surface of the steel and form a barrier. chromium has a very strong affinity for oxygen, so it prevents iron from trying to combine with oxygen (= rusting) .

The chromium oxide is a very thin layer which doesn’t spall off, and it prevents further oxidation of the stainless steel. So even if stainless steel is scratched and the chromium oxide layer is removed, a new chromium oxide layer will form and protect the rest of the stainless steel beneath it. As long as there is sufficient chromium present, the chromium oxide layer will continue to protect the stainless steel and prevent it from rusting.

What is the cause of stainless steel such as SS304 rust?

  • Caused by contacting other material

If the metal such as iron is left on the surface of the stainless steel, the metal will rust and the stainless steel itself will rust. Corrosion does not occur only between stainless steels, but also occurs when it contacts metal other than stainless steel.

  • Dirt or moisture 

If dirt or moisture remains on the surface of stainless steel, it will not be able to form a barrier on that area, and it will be prone to rust.

  • Salt

Stainless steel has better corrosion resistance to salt than other metals, but if it is left on the surface it will rust. Depending on the material, stainless steel are generally not suitable for storing salty contents. SUS 316 material also has better corrosion resistance to salt and seawater than SUS 304 Material

  • chemicals such as acids and alkalis

Depending on the type of acid or alkali, the compatibility with stainless steel is poor on certain chemical and rust will occur. In addition, the compatibility will also change depending on the concentration and temperature of the chemical.

  • Scratches

Rust may occur due to dirt or moisture that has entered the scratched surface. If stainless steel scratched by a metal object, it may also cause rust.

  • Processed Stainless Steel

Water and dirt may accumulate in the processed parts by bending and welding for example, the surface composition may change and become rusty.

How to prevent Stainless Steel become rusty?

  • Prevent dirt, salt (seawater) and moisture

After cleaning, remove dirt and salt, do not leave it in a wet place after cleaning, wipe it off with a dry cloth.

  • Be careful of scratches and other rusty material

We recommend that you handle it in the way that it does not get dirty or deep scratches that collect water, anduse a soft sponge or cloth when cleaning instead of using a metal or hard scrubber. Also, avoid contact with other metal easily rusts to prevent rusting.


We supply various form of stainless steel product in Malaysia and it is available in our online store,  SS304 Wire Mesh, SS316 Wire Mesh, SS304 & SS316 Ball, SS304 Round Bar, SS304 Float Valve, SS304 Pipe Repair Clamp, SS304 PVC curtain hanger, SS304 wire, SS316 wire, SS304 Shim Plate