What measures are required when using austenitic stainless steel in hydrogen sulfide-containing media?
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When carbon steel or low-alloy steel is used in wet hydrogen sulfide environments, post-weld heat treatment is required to prevent intergranular corrosion. As for austenitic stainless steel used in hydrogen sulfide-containing environments, it also has a tendency to suffer from stress corrosion cracking, and post-weld heat treatment is generally not applied to austenitic stainless steel. So what measures should be taken to prevent stress corrosion cracking?
Carbon steel and low-alloy steel suffer from stress corrosion in hydrogen sulfide-corrosive environments. Austenitic stainless steels suffer from stress corrosion in hydrogen sulfide-corrosive environments; careful material selection is necessary, and the use of high-nickel stainless steels can reduce their susceptibility to stress corrosion.
Austenitic stainless steels can undergo stabilization heat treatment or solution treatment to prevent intergranular corrosion
Generally, in environments where H2S levels are greater than 50×10-6, high-quality grades such as 20R and 16MnR should be used to resist stress corrosion. The equipment must undergo post-weld heat treatment, with a hardness level not exceeding HB200; the microstructure should consist of ferrite plus pearlite； In environments where H2S is greater than 500×10-6 and cyanides are greater than 20×10-6, a 20R or 16MnR+0Cr13Al composite shell with 0Cr13 used for the internal components is recommended. In H2S+H2O environments, 18-8 steel is generally not used, nor can 18-8 welding electrodes be used to weld carbon steel or low-alloy steel. If austenitic stainless steel is used, cold working is not possible, and the hardness value must not exceed HRC 20.5; otherwise, stress corrosion is likely to occur.
In a hydrogen sulfide environment, stainless steel primarily suffers from stress corrosion. To address intergranular corrosion or stress corrosion in stainless steel, methods such as selecting appropriate materials, applying surface treatments (passivation), carrying out heat treatment (solution treatment), adding corrosion inhibitors to the medium, or employing external protection methods (cathodic protection or anodic protection) can be used.
Does hydrogen sulfide cause intergranular corrosion in austenitic stainless steel?
The key also depends on the operating temperature and the environmental medium.