Discussing chloride ion stress corrosion and preventive measures

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Stainless steel suffers from stress corrosion in a corrosive medium environment containing oxygen and chloride ions. Stress corrosion failure accounts for about 45% of cases. Common protective measures: Proper material selection – Materials resistant to stress corrosion include high-purity austenitic chromium-nickel steel, high-silicon austenitic chromium-nickel steel, high-chromium ferritic steel, and ferritic-austenitic duplex steel. Among them, ferrite-austenite duplex steel has the best resistance to stress corrosion. Control stress: During assembly, minimize stress concentration and ensure that the areas in contact with the medium have minimal residual stress, in order to prevent scratches and dents; strictly follow the welding procedure specifications. Strictly adhere to operating procedures: strictly control process parameters such as raw material composition, flow rate, medium temperature, pressure, and pH value. Add a corrosion inhibitor within the limits permitted by the process conditions. When using chromium-nickel stainless steel in chlorides containing dissolved oxygen, the mass fraction of oxygen should be reduced to below 1.0×10^-6. Practice has shown that in water with a chloride ion mass fraction of 500.0 ×10^-6, adding a mixture of nitrate with a mass fraction of 150.0 ×10^-6 and sodium sulfite with a mass fraction of 0.5 ×10^-6 yields good results.