In the case of general heat treatment and welding, there will be no carbide precipitation, which eliminates the risk of intergranular corrosion after general heat treatment and welding. Due to the high content of chromium, nickel and molybdenum and the addition of copper, 904L can be passivated even in reducing environments such as sulfuric acid and formic acid. The high nickel content makes it have a lower corrosion rate in the active state. In pure sulfuric acid in the concentration range of 0~98%, the operating temperature of 904L can be as high as 40 degrees Celsius. In pure phosphoric acid in the concentration range of 0-85%, its corrosion resistance is very good. In the industrial phosphoric acid produced by the wet process, impurities have a strong influence on the corrosion resistance. Among all kinds of phosphoric acid, 904L has better corrosion resistance than ordinary stainless steel. Among the strong oxidizing nitric acid, 904L has lower corrosion resistance than high-alloyed steel without molybdenum. In hydrochloric acid, the use of 904L is limited to a lower concentration of 1-2%. In this concentration range. The corrosion resistance of 904L is better than that of conventional stainless steel. 904L steel has high resistance to pitting corrosion. Its crevice corrosion resistance in chloride solution is also very good. The high nickel content of 904L reduces the corrosion rate at the pits and crevices. Ordinary austenitic stainless steel may be sensitive to stress corrosion in a chloride-rich environment when the temperature is higher than 60 degrees Celsius. By increasing the nickel content of stainless steel, this sensitization can be reduced. Due to the high nickel content, 904L has high resistance to stress corrosion cracking in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments.