All metals react with oxygen in the atmosphere, forming an oxide film on the outside. Unfortunately, the iron oxide formed on the plain carbon steel continues to oxidize, causing the rust to expand and eventually form holes. Paint or oxidation-resistant metals such as zinc, nickel and chromium can be electroplated to coat the outside of carbon steel, but, as is known, this protection is only a thin film. If the protective layer is damaged, the steel underneath will begin to rust.
The corrosion resistance of stainless steel depends on chromium, but because chromium is one of the components of steel, the protection methods are not the same.
When the amount of chromium added reaches 10.5%, the atmospheric corrosion resistance of the steel increases significantly, but when the chromium content is higher, although the corrosion resistance can still be improved, it is not obvious. The reason is that when the steel is alloyed with chromium, the type of outer oxide is changed to be similar to the outer oxide formed on pure chromium metal. This carefully adhered chromium-rich oxide protects the outside from further oxidation. This oxide layer is extremely thin, through which you can see the natural luster of the outside of the steel, so that the stainless steel has the outside. Moreover, if the surface is damaged, the exposed steel outside will repair itself with the atmospheric response, forming this "passivation film" and continuing to protect and affect
Stainless steel is one of the most common materials used in a variety of industrial and household applications. One of the main reasons for its popularity is its remarkable corrosion resistance. Corrosion is a chemical process that occurs when a metal reacts with the surrounding environment, leading to its deterioration and often a loss of function. However, stainless steel is designed to resist corrosion, making it a preferred material for many applications. In this blog post, we will discuss why stainless steel is corrosion-resistant.
1. Chromium Content
Stainless steel contains at least 10.5% chromium, which is a key element that makes it corrosion-resistant. Chromium reacts with oxygen in the air to form a passive layer of chromium oxide on the surface of the steel. This layer is only a few atoms thick but is dense and stable, preventing further oxidation and corrosion.
2. Other Alloying Elements
Besides chromium, stainless steel can contain other alloying elements such as nickel, molybdenum, and titanium. These elements enhance the corrosion resistance and improve the mechanical properties of the material. For example, nickel is used to increase the resistance to acids, while molybdenum enhances the resistance to pitting and crevice corrosion.
3. Non-Reactive Surface
Stainless steel has a non-reactive surface, which means that it does not react with most chemicals. This is because the surface is protected by the chromium oxide layer, which prevents chemical reactions with the metal underneath. As a result, stainless steel is commonly used in the food and medical industries, where hygiene and cleanliness are critical.
4. Easy to Clean
Stainless steel is easy to clean, which helps prevent corrosion. Because it has a smooth, non-porous surface, it does not trap dirt, grime, or bacteria. In addition, stainless steel can withstand harsh cleaning agents without corroding, making it a preferred material in industries where sanitation is essential.
5. Self-Healing Properties
Stainless steel has self-healing properties, which means that if the protective oxide layer is damaged, it can repair itself. When the steel is exposed to oxygen again, the chromium reacts with it to form a new oxide layer, restoring the corrosion resistance. This process is known as passivation and makes stainless steel an excellent choice for outdoor structures.
Conclusion
Stainless steel's corrosion resistance is due to a combination of factors, including its chromium content, other alloying elements, non-reactive surface, ease of cleaning, and self-healing properties. By preventing or slowing down corrosion, stainless steel is an ideal material for a wide variety of applications, from medical instruments and food processing equipment to high-rise buildings and bridges.
