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3 main factors affecting the corrosion of stainless steel

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3 main factors affecting the corrosion of stainless steel

May 24, 2019


1. Content of alloying elements.
Generally speaking, steel with a chromium content of 10.5% is not easy to rust. The higher the content of chromel, the better the corrosion resistance. For example, the content of nickel in 304 material should be 8-10%, and the content of chromium should be 18-20%, so that the stainless steel will not rust under normal circumstances.

2, the smelting process of the production enterprises will also affect the corrosion resistance of stainless steel.
Smelting technology, advanced equipment, advanced technology of large stainless steel factory whether in the alloying element control, removal of impurities, billet cooling temperature control can be guaranteed, so the product quality is stable and reliable, internal quality is good, not easy to rust. Conversely, some small steel equipment backward, backward technology, smelting process, impurities can not be removed, the production of products will inevitably rust.

3. External environment, dry and ventilated environment is not easy to rust.
And air humidity, continuous rainy weather, or the environment in the air with high ph is easy to rust. 304 stainless steel, will rust if the environment is too bad.
How should spot of occurrence rust of stainless steel handle?
1. Chemical methods
After pickling, in order to remove all contaminants and acid residues, it is important to properly rinse with water. After all processing with polishing equipment re – polishing, polishing wax can be closed. To local have slight rustily spot also can use the mixture of the gasoline of 1:1, engine oil to wipe with clean dishcloth rustily spot can.
2. Mechanical method
Sand blasting, shot blasting with glass or ceramic particles, annihilation, scrubbing and polishing. It is mechanically possible to erase contamination from previously removed material, polishing material, or annihilation material. All kinds of pollution, especially foreign iron particles, can be a source of corrosion, especially in humid environments. Therefore, mechanical surface cleaning should preferably be carried out under normal dry conditions. The use of mechanical methods can only clean its 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.
Gauge commonly used stainless steel brand and performance
1, 304 stainless steel. It is one of the austenitic stainless steels with large application amount and wide application range. It is suitable for manufacturing deep-drawing forming parts, acid conveying pipes, containers, structural parts, various instrument bodies, etc. It can also be used for manufacturing non-magnetic and low-temperature equipment and parts.
2. 304L stainless steel. In order to solve the problem that 304 stainless steel has severe intergranular corrosion tendency due to the precipitation of Cr23C6 in some conditions, the sensitized ultra-low carbon austenitic stainless steel has significantly better intergranular corrosion resistance than 304 stainless steel. In addition to slightly low strength, other performance with 321 stainless steel, mainly used for welding and can not be solid solution treatment of corrosion resistant equipment and components, can be used for manufacturing various types of instrument body.
3. 304H stainless steel. 304 stainless steel internal branch, carbon mass fraction in 0.04% – 0.10%, high temperature performance is better than 304 stainless steel.
4. 316 stainless steel. Molybdenum is added to 10Cr18Ni12 steel to make it have good resistance to reducing medium and point corrosion. In seawater and other media, corrosion resistance is better than 304 stainless steel, mainly used for corrosion resistance materials.
5. 316L stainless steel. Ultra-low carbon steel, with good resistance to intercrystalline corrosion, is suitable for manufacturing thick section size welding parts and equipment, such as petrochemical equipment corrosion resistant materials.
6. 316H stainless steel. Internal branch of 316 stainless steel, carbon mass fraction in 0.04% – 0.10%, high temperature performance is better than 316 stainless steel.
7, 317 stainless steel. The pitting and creep resistance of 316L stainless steel is better than that of 316L stainless steel.
8, 321 stainless steel. Austenitic stainless steels stabilized with titanium can be replaced by ultra-low carbon austenitic stainless steels. It is generally not recommended except for special occasions such as high temperature or hydrogen corrosion resistance.
9, 347 stainless steel. Niobium stabilization of austenitic stainless steel, add niobium improve the intergranular corrosion resistance, acid, alkali, salt and other corrosive medium in the corrosion resistant 321 stainless steel, welding performance is good, can make corrosion resistant materials and can be used for heat resistant steel, mainly used in thermal power, petrochemical fields, such as the production of container, piping, heat exchanger, axial, industrial furnace furnace and furnace tube in the thermometer, etc.
10. 904L stainless steel. Super austenitic stainless steel, completely is Finland otto kun’s (OUTOKUMPU) company invented a kind of super austenitic stainless steel, nickel its mass fraction is 24% a 26%, carbon mass fraction is less than 0.02%, excellent corrosion resistance, in the oxidizing acid such as sulfuric acid, acetic acid, formic acid, phosphoric acid have good corrosion resistance, also has good resistance crevice corrosion and stress corrosion resistance. Used in various concentration of sulfuric acid under 70 ℃, under ordinary conditions of any concentration, temperature resistance of acetic acid and formic acid and acetic acid in mixed acid corrosion resistance is very good also. The original standard, asmesb-625, classifies it as a nickel-based alloy, while the new standard classifies it as stainless steel. China only has approximately brand 015Cr19Ni26Mo5Cu2 steel. A few European instrument manufacturers use 904L stainless steel as the key material. For example, the measuring tube of E+ H mass flow meter is made of 904L stainless steel, and the case of rolex watch is also made of 904L stainless steel.
11. 440C stainless steel. Martensitic stainless steel, in the quenchable stainless steel, stainless steel hardness is the highest, HRC57. It is mainly used for making spool, seat, sleeve and stem of nozzle, bearing and valve.
12, 17-4ph stainless steel. Martensitic precipitation hardening stainless steel, hardness of HRC44, high strength, hardness and corrosion resistance, cannot be used for temperature higher than 300 ℃. Good corrosion resistance to atmosphere and dilute acid or salt, its corrosion resistance and 304 stainless steel and 430 stainless steel, used in the manufacture of offshore platforms, turbine blades, valve spool, valve seat, sleeve, stem and so on.

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