316L corrosion resistance
As a molybdenum-containing stainless steel, 316L stainless steel has better corrosion resistance than 304 stainless steel, and the production equipment for pulp and papermaking has excellent corrosion resistance. And 316 stainless steel is also resistant to corrosion from the ocean and corrosive industrial atmosphere. It has high heat resistance. In intermittent use below 1600 degrees and continuous use below 1700 degrees, 316L stainless steel has good oxidation resistance. Within the range of 800-1575 degrees, it is best not to continuously operate 316L stainless steel products. However, when 316 stainless steel is continuously used outside this temperature range, it has good heat resistance.
The resistance to carbide precipitation of 316L stainless steel is better than that of 316 stainless steel, and it can be used in the above temperature range. 316L is a low-C series of 316 steel. In addition to having the same characteristics as 316 steel, 316L has excellent resistance to grain boundary corrosion. It is a product that has special requirements for resisting grain boundary corrosion among the uses of 316 steel.
304 corrosion resistance
304 stainless steel is a high alloy steel that can resist corrosion in air or chemically corrosive media. 304 stainless steel has excellent corrosion resistance and intergranular corrosion resistance. For oxidizing acids, the experimental results are: 304 stainless steel has strong corrosion resistance in nitric acid below the boiling temperature with a concentration of ≤65%. It also has good corrosion resistance to alkali solutions and most organic and inorganic acids.
There are several main reasons why 304 stainless steel rusts. First, there are chloride ions in the use environment; second, the stainless steel has not undergone solid solution treatment. , the alloy elements are not dissolved into the matrix, resulting in a low alloy content in the basic structure and poor corrosion resistance; thirdly, this material that does not contain titanium and niobium has a natural tendency for intergranular corrosion. Adding titanium and niobium, coupled with stabilization treatment, can reduce intergranular corrosion.
In addition, the main difference in chemical composition between 316L and 304 stainless steel is that 316L stainless steel contains molybdenum. Adding the alloying element molybdenum to austenitic stainless steel can enhance the thermal strength and creep strength of stainless steel. Improve its ability to resist pitting corrosion and intergranular corrosion.
Molybdenum can passivate the surface of stainless steel in reducing and strongly oxidizing salt solutions, and can improve corrosion resistance and prevent pitting corrosion of steel in chloride solutions. Adding Mo can improve the resistance to reducing acids and pitting corrosion, and reducing the carbon content can improve the resistance to intergranular corrosion and improve welding performance.
Adding molybdenum element can better prevent pitting corrosion. 304 is a low carbon stainless steel and 316L is an ultra-low carbon stainless steel. The lower carbon content can reduce the occurrence of intergranular corrosion, but both 304 and 316L are more sensitive to Cl particles. The ability of 304 to resist cl- is weaker than that of 306L, so in environments with relatively high CL- content, usually It uses 316L.