What are the application areas of different types of stainless steel? How to deal with stainless steel after rust?

Stainless steel is short for stainless steel, resistant to air, steam, water and other weak corrosion media or stainless steel with stainless steel, and the chemical corrosion medium (acid, alkali, salt and other chemical corrosion) corrosion of steel is called acid steel. Due to the difference in the chemical composition of the two, their corrosion resistance is different, ordinary stainless steel is generally not resistant to chemical medium corrosion, and acid-resistant steel is generally stainless. The following is a brief introduction to the performance and application range of the following commonly used stainless steel:

304 stainless steel

304 stainless steel is the most common steel, as a widely used steel, has good corrosion resistance, heat resistance, low temperature strength and mechanical properties; Stamping, bending and other hot processing is good, no heat treatment hardening phenomenon (non-magnetic, then use the temperature -196℃ ~ 800℃).

Scope of application: Household goods (1, 2 types of tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs); Auto parts (windshield wipers, mufflers, molding products); Medical equipment, building materials, chemicals, food industry, agriculture, Marine components

304L stainless steel (L is low carbon)

As a low-carbon 304 steel, in the general state, its corrosion resistance is similar to 304 steel, but after welding or stress relief, its grain boundary corrosion resistance is excellent; In the absence of heat treatment, it can also maintain good corrosion resistance, and the use temperature is -196℃ ~ 800℃.

Scope of application: Used in chemical, coal and petroleum industry with high grain boundary corrosion resistance, heat resistant parts of building materials and parts with difficulty in heat treatment.

316 stainless steel

316 stainless steel due to the addition of molybdenum, so its corrosion resistance, atmospheric corrosion resistance and high temperature strength is particularly good, can be used under harsh conditions; Excellent work hardening (non-magnetic).

Scope of application: seawater equipment, chemical, dye, paper, oxalic acid, fertilizer and other production equipment; Photography, food industry, coastal facilities, ropes, CD rods, bolts, nuts.

316L stainless steel (L is low carbon)

Performance description: As a low-carbon series of 316 steel, in addition to having the same characteristics as 316 steel, its grain boundary corrosion resistance is excellent.

Scope of application: Products with special requirements for resistance to grain boundary corrosion.

Why does stainless steel rust?

Why does stainless steel rust? When the surface of the stainless steel pipe appears brown rust spots (spots), people are surprised: think that "stainless steel is not rusty, rust is not stainless steel, there may be a problem with the steel." In fact, this is a one-sided wrong view of the lack of understanding of stainless steel. Stainless steel will rust under certain conditions.

Stainless steel has the ability to resist atmospheric oxidation - that is, rust, but also has the ability to resist corrosion in the medium containing acid, alkali, salt - that is, corrosion resistance. However, the size of its corrosion resistance is changed with the chemical composition of the steel itself, the protection state, the use conditions and the type of environmental media. Such as 304 steel pipe, in a dry and clean atmosphere, has absolutely excellent corrosion resistance, but it is moved to the seaside area, in the sea fog containing a lot of salt, it will soon rust; The 316 steel pipe performed well. Therefore, not any kind of stainless steel, in any environment can resist corrosion, does not rust.

What kind of stainless steel is not easy to rust?

There are three main factors affecting stainless steel corrosion:

1, the content of alloying elements

Generally speaking, the content of chromium is 10. 5% steel is not easy to rust. The higher the content of chromium nickel, the better the corrosion resistance, such as 304 material nickel content in 8-10%, chromium content reached 18-20%, such stainless steel in general circumstances will not rust.

2, production smelting process

Large stainless steel plants with good smelting technology, advanced equipment and advanced technology can be guaranteed whether in the control of alloying elements, the removal of impurities, and the control of billet cooling temperature, so the product quality is stable and reliable, the internal quality is good, and it is not easy to rust. On the contrary, some small steel mills are backward in equipment and technology, and impurities cannot be removed in the smelting process, and the products produced will inevitably rust.

3. External environment

The climate is dry and ventilated environment is not easy to rust, and the air humidity is large, continuous rainy weather, or the environment area with high pH in the air is easy to rust. 304 stainless steel, if the surrounding environment is too poor will rust.

Stainless steel appears rust spot how to deal with?

1. Chemical methods

Use pickling paste or spray to assist its rust parts to re-passivate to form chromium oxide film to restore its corrosion resistance. After pickling, in order to remove all contaminants and acid residues, it is very important to properly rinse with water. After all treatment, re-polish with polishing equipment, and seal with polishing wax. For local slight rust spots can also be used 1:1 gasoline, oil mixture with a clean cloth to wipe rust spots.

2. Mechanical method

Sand blasting, shot blasting with glass or ceramic particles, annihilation, brushing and polishing. With mechanical methods it is possible to erase contamination caused by previously removed, polished or annihilated materials. All kinds of pollution, especially foreign iron particles, can be a source of corrosion, especially in humid environments. Therefore, the mechanical cleaning surface should preferably be cleaned under dry conditions. The use of mechanical methods can only clean the surface, can not change the corrosion resistance of the material itself. Therefore, it is recommended to re-polish with polishing equipment after mechanical cleaning and seal with polishing wax.