904L has good activation-passivation transformation ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, phosphoric acid, and very good corrosion resistance in neutral chloride-containing media Good resistance to pitting corrosion, as well as good resistance to crevice corrosion and stress corrosion. It is suitable for sulfuric acid of various concentrations below 70°C, and it has good corrosion resistance in the mixed acid of formic acid and acetic acid in any concentration and temperature under normal pressure.

Like ordinary stainless steel, 90 4 L can be welded by various welding methods. The most commonly used welding method is manual arc welding or inert gas shielded welding. The electrode or wire metal is based on the composition of the base material and has higher purity, and the content of molybdenum is higher than that of the base material. Generally, preheating is not necessary before welding, but in cold outdoor operations, in order to avoid condensation of water vapor, the joints or adjacent areas can be uniformly heated. Note that the local temperature should not exceed 100°C to avoid carbon accumulation and intergranular corrosion. It is advisable to use small heat input, continuous and fast welding speed when welding. Generally, heat treatment is not required after welding. If heat treatment is required, it must be heated to 110 0~ 1150 ℃ and then quickly cooled.