Corrosion Behavior of Welded Joint of Low Alloy Steel in CO₂-O₂-H₂S-SO₂ Wet Gas Environment

Low alloy steel E36 was welded by different welding technology with different component welding wires. The corrosion behavior of the welded joints of low alloy steels in CO₂-O₂-H₂S-SO₂ moisture environment was studied through corrosion experiment and electrochemical testing. A concept of R-value which means thinning synergy to welded joint was proposed. The experimental results show that the microstructure of the welded joint welded with H08MnA welding wire was composed of polygonal ferrite, acicular ferrite and bainite. And in CO₂-O₂-H₂S-SO₂ moisture environment, the welded joint had a corrosion rate of 0.478 0 mm/a, a corrosion thinning amount of 0.128 3 mm, a corrosion step depth of 46.146 μm(among 30~50 μm), and a step angle of 14.1°(<15°). The electrochemical test results were consistent with the corrosion test results, and met the requirements of IMO standards and China Classification Society's requirements for the corrosion resistance of welded joints on cargo tank decks. The thinning synergy to welded joint enhanced the scientific evaluation of the corrosion behavior of low alloy steels in CO₂-O₂-H₂S-SO₂ moisture corrosion environment.