Top 5 Factors of Stainless Steel Corrosion and Most Effective Prevention Methods
BlogDate: 06-12-2023 by: Ngoc Cam
Stainless steel is famous for its resistance to corrosion and rust thanks to its Chromium and Nickel content of over 12% while its carbon content is very low (below 0.1%). However, under harsh environmental conditions, stainless steel can be affected. So what factors can cause corrosion or rust in stainless steel?
1. Why Stainless Steel is Rust Resistant
When exposed to air, chromium in stainless steel reacts with oxygen to form a very thin layer of chromium oxide that cannot be seen with the naked eye. They act as an extremely strong protective layer and are completely unaffected by water and air. Therefore, the stainless steel is almost completely protected against rust or oxidation.
2. Top 5 Factors Causing Stainless Steel Corrosion
2.1. Strong chlorides can cause pitting corrosion on stainless steel
Some types of stainless steel alloys will corrode extremely when exposed to chloride-rich environments. 304 stainless steel is often used to make specialized equipment serving the navy. During long-term use, the metal begins to pit due to exposure to salt-rich seawater or air
To prevent this situation, manufacturers use stainless steel with special chloride resistance, such as type 316. In addition, the stainless steel surface should be coated with a specialized layer to prevent the alloy from coming into contact with chloride environments.
2.2. Galvanic corrosion caused by welding different stainless steel alloys
One of the most common mistakes that leads to corrosion of stainless steel is welding different metal wires or plates together. The reason is that each type of material has different properties, so when connected through a common electrolyte material, an electric current will flow from one material to the other. This makes it easier for the metal to become an "anode" and accelerates the corrosion process. Corrosion speed also depends on other factors such as the type of stainless steel being welded, the type of welding material, temperature, sensitivity, exposed metal surface area,...
The best way to prevent galvanic corrosion from welding is to avoid connecting two different metals or to seal the weld with a specialized coating to prevent the flow of electrons from the cathode to the anode.
2.3. Coating normal iron or steel onto stainless steel
In some applications, billet or iron residue existing on the surface of stainless steel can break down the protective oxide layer of the stainless steel billet, losing its corrosion resistance and becoming rusty.
Factories need to thoroughly clean welding and cutting equipment, tools or steel brushes before moving on to process new materials. This will limit metallic chips from metals sticking to the stainless steel surface.
2.4. Applying extremely high temperatures to stainless steel
Stainless steel alloys have very high melting points, around 1400 - 1500 degrees Celsius. However, if stainless steel is exposed to high temperatures, it can undergo physical and mechanical changes, affecting its corrosion resistance.
For example, steel alloys exposed to high temperatures during the annealing treatment process can appear to scale and flake off, causing bimetallic corrosion. In addition, too high temperatures also lose the protective oxide layer, increasing the risk of corrosion.
Mills control this corrosion factor by testing the appropriate operating temperature for each grade of stainless steel to see if the temperature used exceeds the limit.
2.5. Other environmental factors
There are many cases where factories can produce stainless steel products to custom specifications to meet customer needs. This accidentally leads to stainless steel being corroded due to some unforeseen environmental factors. For example, products that will be used in coastal areas have higher than normal humidity and chlorides, which will accelerate metal corrosion.
Therefore, when choosing stainless steel as a material for applications, manufacturers must take into account environmental factors to ensure products with good corrosion resistance and durability.
Hopefully, this article on factors that cause stainless steel corrosion has helped you learn more ways to better protect your products. If you have any questions or need to import Vietnamese stainless steel at good prices and quality, please contact MRS Steel via Email: vanloc@mrssteel.com.vn or Whatsapp:+84 76 911 2358.
