When talking about the corrosion resistance of stainless steel, we must first understand the different types of corrosion and their definitions. Stainless steel is popular in part because of its excellent corrosion resistance, but under certain conditions, stainless steel can still be affected by corrosion. This article will take an in-depth look at various stainless steel alloys and how they behave in the face of different types of corrosion such as stress corrosion cracking, point corrosion, intergranular corrosion, crevice corrosion, total corrosion, and uniform corrosion.

Types and definitions of corrosion

1. Stress Corrosion Cracking, SCC
Stress corrosion cracking is a severe type of corrosion that usually occurs when a metal is under stress while exposed to a specific corrosive environment. This corrosion usually manifests as microcracking or cracking of the metal, which can lead to mechanical failure of parts or structures. Different types of stainless steel show different resistance to stress corrosion cracking.

2. Pitting Corrosion
Point corrosion is a type of localized corrosion characterized by the appearance of small, deep pits or holes in the metal surface. This type of corrosion usually occurs in specific environments, such as salt water or chloride-containing media. Point corrosion is easy to form small holes in the stainless steel surface, which may lead to component failure.

3. Intergranular Corrosion
Intergranular corrosion is a type of corrosion characterized by damage to the grain boundary region of the metal. This type of corrosion may reduce the mechanical properties of stainless steel, especially the tensile strength. For stainless steel, intergranular corrosion can be a serious problem, especially for welded areas.

4. Crevice Corrosion
Crevice corrosion usually occurs in the contact areas of metal surfaces, such as between tightly stacked metal plates or tightly connected parts. This corrosion forms in gaps and can lead to local corrosion and damage to parts.5. Uniform Corrosion
Total corrosion is a relatively uniform form of corrosion that covers most areas of the stainless steel surface. Although this corrosion is not as localized as other types, it may still cause visible corrosion on the surface of stainless steel. Uniform corrosion is usually caused by a general chemical environment.
6. General Corrosion
Uniform corrosion is a generally slow corrosion process that covers most areas of the stainless steel surface. It is manifested as gradual corrosion of the metal surface, but the corrosion rate is relatively low. This corrosion is mainly affected by environmental factors.

Corrosion Resistance of Stainless Steel

The following describes the various stainless steel alloys and their properties under different types of corrosion:

• 304 stainless steel: 304 is one of the most commonly used stainless steels. It shows good corrosion resistance under most corrosion conditions, but it has certain sensitivity to point corrosion and stress corrosion cracking.
• 301 Stainless steel: 301 performs well under mildly corrosive conditions, but point corrosion may occur in highly corrosive environments.
• 304L stainless steel: 304L is a low-carbon version of 304, with good intergranular corrosion resistance, suitable for high temperature welding applications.
• 316 stainless steel: 316 is a kind of stainless steel with excellent corrosion resistance and good resistance to point corrosion and intergranular corrosion. This makes it the preferred choice in many corrosive environments.
• 317 stainless steel: 317 has shown good resistance to various corrosive environments, especially suitable for organic acids, chlorides and sulfide environments.
• 321 Stainless steel: 321 shows good corrosion resistance in high temperature environments, resistant to both point corrosion and intergranular corrosion, suitable for manufacturing high temperature equipment.
• 347 Stainless steel: 347 is similar to 321 and has good tolerance to high temperatures and organic acid environments, reducing the risk of intergranular corrosion and point corrosion.
• 302, 302B, 303, 303Se, 305: These stainless steels are slightly different in some ways, but overall, they have some resistance to corrosion, but generally not as resistant as the stainless steel types mentioned above.
• 330 Stainless Steel: 330 is specially designed for high temperature and high heat cycle conditions. It has good resistance to thermal expansion and thermal shock.
• 384 Stainless steel: 384 shows good tolerance in strong oxidizing environments and is suitable for high temperature applications.
• 308, 309, 310, 314: These stainless steels are high alloy stainless steels, usually used in high temperature and strong corrosive environments, such as high temperature furnaces, chemical plants, etc.

Corrosion Protection of Stainless Steel

The corrosion resistance of stainless steel depends on a number of factors, including alloy composition, environmental conditions and material handling. In order to enhance the corrosion resistance of stainless steel, the following measures can be taken:

• Select the appropriate type of stainless steel: According to the specific use environment, select the appropriate type of stainless steel to ensure the best corrosion resistance.
• Use a coating: For some applications, consider using a coating to provide additional protection.
• Avoid corrosive environment: Where possible, try to avoid placing stainless steel in a corrosive environment, or take measures to reduce the corrosion factor.
• Regular maintenance and cleaning: Keep the stainless steel surface clean and maintain it regularly to extend its service life.

Stainless steel is an excellent material with excellent corrosion resistance. However, it is essential to understand the different types of corrosion and the best corrosion resistance applicable to various types of stainless steel. Only through the right material selection and appropriate protective measures can we ensure that stainless steel maintains its performance and beauty in a variety of harsh environments.

Whether in aerospace, chemical, medical, construction or daily life, stainless steel plays an indispensable role. By understanding the corrosion characteristics and protection methods of stainless steel, we can better cope with corrosion problems and ensure the reliability and durability of stainless steel products.