Corrosion Performance of Welded Joints for E40 Marine Steel

Abstract

Marine steel requires excellent toughness and corrosion resistance in a low-temperature seawater environment. In this study, corrosion tests on E40 steel were performed, including electrochemical testing of the weld metal and heat-affected zone, dynamic corrosion testing in a simulated seawater environment, and the analysis and comparison of results obtained using different methods. The corrosion resistance of E40 was determined by measuring the saturation current density of the anodic dissolution of the steel in a corrosive medium by an electrochemical method. Under laboratory conditions, the corrosion resistance was investigated under simulated seawater. The results showed that regions with uneven microhardness corresponded to the inhomogeneity of the corrosion potential, with measured fluctuations of up to 40 mV. Nanoscale corrosive–aggressive non-metallic inclusions served as a substrate for the deposition of titanium and niobium carbonitrides, thereby weakening the corrosion resistance. The corrosion rate of the base metal was 1.16–1.64 mm/year, which was slightly higher than that of the heat-affected zone. The influence of deposition on the corrosion performance of welded joints under different deoxygenation processes was studied, and the deposition composition was controlled by a deoxygenation process to improve the corrosion resistance of the steel plate.

Keywords

• marine steel
• welded joints
• microstructure
• current density
• corrosion resistance