Microstructural study and electrochemical behavior of low alloy steel weldment

Submerged arc welding (SAW) was applied to SA516 (Grade 70) pressure vessel and boiler steel. The microstructural and electrochemical corrosion study of base metal (BM), weld zone (WZ) and heat affected zone (HAZ) was carried out to understand the effect of welding cycle by optical microscopy, X-ray diffraction (XRD), potentiodynamic polarization and linear polarization resistance (LPR) method to correlate corrosion kinetic parameters with microstructural changes in tap water and 0.5% (w/v) NaCl solution under plain and aeration conditions at room temperature. From microstructural study, the morphology of ferrite in WZ and HAZ showed different electrochemical behavior and corrosion rate than that of BM.