Types of Stainless Steel - What Keeps Them from Rusting?
What makes stainless steel unique when compared to regular steel? Both are steel materials that have applications in various industries. However, the primary difference between stainless and regular steel is the chromium content in each steel. Depending on the types of stainless steel, all of them have at least 10% chromium content, which covers the surface area to prevent rust or corrosion. In contrast, regular steel doesn’t have any chromium, making it susceptible to corrosion.
Both regular steel and stainless steel have iron as their primary material, and iron can get rusted from time to time because of the oxidation process on the metal surface. However, the oxidation process can’t erode the iron content inside the stainless-steel material because of the chromium surface layer.
Can Types of Stainless Steel Develop Rust?
Most stainless-steel materials will not develop rust or corrosion because of the chromium surface layer they have. The chromium surface layer will prevent any oxidation on the surface of the stainless-steel materials, which is why they can’t get rusted. However, sometimes, stainless steel can still develop rust when it gets exposed to certain things. Here are some factors that can cause stainless steel to develop rust:
Prolonged exposure to certain chemicals.
Stainless steel might not rust immediately when exposed to certain chemicals. However, prolonged exposure to certain chemicals can cause stainless steel to get corroded from time to time. These chemicals include sulphuric acids and hydrochloric acids.
Scratched or damaged surface.
The chromium surface layer of stainless steel can prevent it from getting corroded. So, when the chromium surface gets scratched or damaged, corrosion can still seep into the stainless-steel material and cause rusting from time to time.
Prolonged exposure to heat and moisture.
Other factors which can cause stainless steel to rust are heat and moisture. Of course, you need to expose the stainless-steel material to heat and moisture for a prolonged period. Exposing the stainless-steel material to a high temperature and putting it in a moisture-filled area will put the stainless steel in a gradual corrosion process.
Lack of chromium content.
The lower the chromium content in a stainless-steel material, the weaker its corrosion resistance will be. The lack of chromium content can cause the stainless-steel material to rust, as there’s only a thin layer of chromium on the stainless-steel surface, which is not enough to protect it from oxidation.
Things You Can Do to Keep Stainless Steel from Rusting
The bigger the chromium content of the stainless steel, the higher its corrosion resistance level. As you might already know, corrosion can still happen even in stainless-steel materials. However, the rusting process in stainless steel is much slower than in steel or iron, and of course, you can always prevent corrosion by doing certain things. Here are the things you can do to keep stainless steel from rusting:
Use stainless-steel material with higher chromium content.
To minimize the potential of rusting, you can use stainless-steel material with higher chromium content. This can give the stainless-steel surface even better protection against corrosion and rust.
Don’t expose it to certain chemicals, high temperatures, and moisture.
Certain chemicals, high temperatures, and high moisture levels can speed up the rusting process of stainless steel. So, avoid exposing the stainless-steel material to these conditions.
Perform regular maintenance on types of stainless steel.
Stainless steel also needs regular maintenance to ensure the surface is always corrosion-free. You can clean the stainless-steel material using soap and warm water and then follow the process by applying a rust-resistant coating.
Keep the surface free from iron or steel materials during fabrication.
During fabrication such as CNC turning and sheet metalwork process, contact with iron or steel materials on the stainless-steel surface can cause it to corrode much faster because the iron or steel materials will contaminate the stainless-steel surface. Be sure to avoid contacting any iron or steel during the stainless-steel fabrication process to create the best corrosion-resistant surface for the stainless steel.
Various Types of Stainless Steel
There are various types of stainless steel used for various industrial applications. Each type of stainless steel has its characteristics, with different hardness levels, chromium content, carbon content, and the level of corrosion resistance. Here are various types of stainless steel:
Austenitic stainless steel.
This type of stainless steel, which most industries use nowadays, features stronger protection against corrosion and rust. The austenitic stainless steel has a minimum of 16% chromium content and incorporates a maximum of 0,15% carbon.
Martensitic stainless steel.
Martensitic stainless steel has a lower chromium level on its surface than austenitic stainless steel. Thus it is much less corrosion-resistant than the austenitic type. The amount of chromium in martensitic stainless steel is around 11.5% - 13%, with around 0.1% of manganese and 0.15% of carbon.
Ferritic stainless steel.
Ferritic stainless steel is also the type of stainless steel that has less corrosion resistance when compared to austenitic stainless steel. However, it is still better than martensitic stainless steel. It contains around 10.5% to 30% chromium and less than 0.20% carbon.
Duplex stainless steel.
Duplex stainless steel is a type of stainless steel that combines austenitic and ferritic stainless steel. It has a mixture of 50% austenitic and 50% ferritic stainless steel.
Precipitation-hardened stainless steel.
This type of stainless steel has a higher hardness and anti-corrosion level than austenitic stainless steel. To produce the precipitation-hardened stainless steel, you need to perform the precipitation process to create the hardened stainless-steel surface.
Conclusion
Despite its corrosion-resistant characteristics, stainless steel can still get corroded when exposed to certain things for a prolonged period, such as chemicals, heat, moisture, and more. However, by keeping the stainless steel in its best condition, you can always prevent any corrosion from happening on the stainless-steel surface.
Various types of stainless steel are also used in various industrial applications, with different levels of corrosion resistance, hardness, and other characteristics. It’s always best for you to choose stainless-steel materials that can provide you with the best corrosion-resistant properties to avoid any unwanted corrosion later.
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