Abstract
The stress corrosion cracking (SCC) and hydrogen embrittlement cracking (HEC) characteristics of welded weathering steel and carbon steel were investigated in aerated acid chloride solution. The electrochemical properties of welded steels were investigated by polarisation and galvanic corrosion tests. Neither weathering steel nor carbon steel showed passive behaviour in this acid chloride solution. The results indicated that weathering steel had better corrosion resistance than carbon steel. Galvanic corrosion between the weldment and the base metal was not observed in the case of weathering steel because the base metal was anodic to the weldment. However, the carbon steel was susceptible to galvanic corrosion because the weldment acts as an anode. Slow strain rate tests (SSRT) were conducted at a constant strain rate of 7.87 × 107 s-1 at corrosion potential, and at potentiostatically controlled anodic and cathodic potentials, to investigate the SCC and HEC properties in acid chloride solution. The welded weathering steel and carbon steel were susceptible to both anodic dissolution SCC and hydrogen evolution HEC. However, weathering steel showed less susceptibility of SCC and HEC than carbon steel at anodic potential because of Cr and Cu compounds in the rust layer, which retarded anodic dissolution, and at cathodic potential due to the presence of Cr, Cu, and Ni in alloy elements, which inhibit the reduction of hydrogen ions. SEM fractographs of both steels revealed a quasicleavage fracture in the embrittled region at applied anodic and cathodic potentials.
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