Comparison of corrosion resistance between 304 and 316L stainless steel

[guidebook] : As a molybdenum-containing stainless steel, 316L stainless steel has better corrosion resistance than 304 stainless steel, and has excellent corrosion resistance in the manufacture of pulp and paper production equipment. And 316 stainless steel is also resistant to marine and aggressive industrial atmospheres. Heat resistance is very high, in the intermittent use of 1600 degrees below and in the continuous use of

316L corrosion resistance

As a molybdenum-containing stainless steel, 316L stainless steel has better corrosion resistance than 304 stainless steel, and has excellent corrosion resistance in the manufacture of pulp and paper production equipment. And 316 stainless steel is also resistant to marine and aggressive industrial atmospheres. Heat resistance is very high, in the intermittent use of 1600 degrees below and in the continuous use of 1700 degrees below, 316L stainless steel has good oxidation resistance. In the range of 800-1575 degrees, it is best not to work continuously 316L stainless steel products, but in the continuous use of 316 stainless steel outside this temperature range, it has good heat resistance.

316L stainless steel carbide precipitation resistance is better than 316 stainless steel, available in the above temperature range. 316L as a 316 steel low C series, in addition to the same characteristics with the 316 steel, its resistance to grain boundary corrosion. It is a product with special requirements for grain boundary corrosion resistance in the use of 316 steel.

304 corrosion resistance

304 stainless steel is able to resist corrosion in air or chemical corrosive media can resist corrosion of a high-alloy steel, 304 stainless steel stainless steel corrosion resistance and resistance to intergranular corrosion properties are excellent. For oxidizing acids, the experimental results are: the concentration ≤ 65% of the boiling temperature below the nitric acid, 304 stainless steel has a strong corrosion resistance. For alkali solutions and most organic and inorganic acids also have good corrosion resistance.

304 stainless steel rust reasons are mainly several, one is the presence of chloride ions in the use of the environment; Second, the stainless steel is not solid solution treatment, the alloying elements are not dissolved into the matrix, resulting in the basic organization of the alloy content is low, the corrosion resistance is poor; The third is that this does not contain titanium and niobium materials have an inherent tendency to corrosion of the intergranular corrosion. Add titanium and niobium, coupled with stabilization treatment, can reduce intergranular corrosion.

In addition 316L and 304 stainless steel in the chemical composition of the most important difference is 316L stainless steel containing molybdenum. In the austenitic stainless steel alloying element molybdenum, can enhance the thermal strength and creep strength of stainless steel. Improve its resistance to pitting and intergranular corrosion.

Molybdenum in reducing and strong oxidizing salt solutions can make the stainless steel surface passivation, can improve corrosion resistance to prevent pitting corrosion of steel in chloride solutions. Adding Mo can improve the resistance to reducing acid and pitting resistance, reduce the carbon content can improve the resistance to intergranular corrosion and improve welding performance.

The addition of molybdenum can better prevent pitting, 304 belongs to low carbon stainless steel and 316L belongs to ultra-low carbon stainless steel. The lower carbon content can reduce the occurrence of intergranular corrosion, but no matter 304 or 316L is more sensitive to Cl particles, 304's ability to resist cl- is weaker than 306L, so in the CL-content of the environment is relatively high, it is usually used 316L.