Comparative analysis of corrosion resistance of SUS316L stainless steel and SUS304 stainless steel
SUS316L stainless steel relative to SUS304 stainless steel has a feature, that is, contains molybdenum element, from this point of view, we can basically conclude that the corrosion resistance of SUS316L stainless steel is better than the corrosion resistance of SUS304 stainless steel. SUS316L stainless steel has good corrosion resistance in the pulp and paper production process. And SUS316L stainless steel is also resistant to the erosion of the ocean and aggressive industrial atmosphere. Heat resistance in the intermittent use below 1600 degrees and in the continuous use below 1700 degrees, SUS316L stainless steel has good oxidation resistance.
Between this we should note that in the range of 800-1575 degrees, it is best not to continuously act on SUS316L stainless steel, but in the continuous use of SUS316L stainless steel outside this temperature range, the stainless steel has good heat resistance. The resistance to carbide precipitation of SUS316L stainless steel is better than that of SUS316 stainless steel, available in the above temperature range.
SUS316L stainless steel is the low C series of 316 stainless steel, in addition to having the same characteristics as 316 stainless steel, its resistance to grain boundary corrosion is excellent.
After talking about the corrosion resistance of SUS316L stainless steel, we will talk about another protagonist of this article, in fact, in principle, SUS304 stainless steel has excellent corrosion resistance and good intergranular corrosion resistance. SUS304 stainless steel has strong corrosion resistance to oxidizing acids, such as nitric acid with a concentration of ≤65% below the boiling temperature. It also has good corrosion resistance to alkaline solutions and most organic and inorganic acids. Therefore, it is good to say that it is a high alloy steel that can resist corrosion in air or chemical corrosive media.
Here we also talk about the anti-rust properties of SUS304 stainless steel, stainless steel is a beautiful surface and good corrosion resistance, do not have to go through plating and other surface treatment, and play the inherent surface properties of stainless steel, used in many aspects of steel. The mechanism of stainless steel rust prevention is that alloying elements form a dense oxide film, isolating oxygen contact and preventing continued oxidation. From this point of view, it is easy to realize that stainless steel is not "stainless". Why do some SUS304 stainless steel still have rust phenomenon? There are three reasons:
(1) The presence of chloride ions in the use environment. Chloride ions are widely present, such as salt, sweat, sea water, sea breeze, soil and so on. Stainless steel in the presence of chloride ions in the environment, corrosion quickly, even more than ordinary mild steel, so there are requirements for the use of stainless steel environment, and often need to wipe, dust out, keep clean and dry.
(2) No solid solution treatment. The alloying elements do not dissolve into the matrix, resulting in low alloying content and poor corrosion resistance of the basic structure.
(3) This material, which does not contain titanium and niobium, has a natural tendency to intergranular corrosion. The intergranular corrosion can be reduced by adding titanium and niobium and then stabilizing them.
