In seawater pipeline, the welding joint is a non-uniform structure composed of welding seam, base metal and heat affected zone. It has inhomogeneity in chemical composition, organizational structure, residual stress, etc. As local defects and high turbulence accelerate corrosion, the welding joint is often the weakest link in pipeline corrosion. Herein, the electrochemical corrosion behavior of B10 alloy welded joint in flowing seawater is studied from macroscopic and submicroscopic viewpoints using AC impedance, linear polarization, array electrode and morphological characterization. The results reveal that the corrosion rate of weld metal (WM), base metal (BM) and heat-affected zone (HAZ) decreased with the increase of time. Combined with SEM and EDS analysis, it can be seen that the increase in time led to the decomposition and accumulation of corrosion products, which gradually enhanced the corrosion resistance of welded joints. At the submicroscopic scale, WM acts as a cathode to mitigate corrosion during the later stages of high flow rate.

To prolong the service time of ship and seawater piping systems, titanium alloys have a series of excellent properties, such as their low density, high strength, and seawater corrosion resistance, and they have become the main material used in ocean engineering. A welded joint is a nonuniform structure that is composed of a weld seam (WM), base metal (BM), and heat-affected zone (HAZ). When an alloy is used, it is easier to form galvanic corrosion, stress corrosion, and pitting corrosion in a weld joint than when a single metal is used. Therefore, corrosion failure often occurs at a welded joint. In this article, classical electrochemical testing (EIS and Tafel) and surface morphology analysis (SEM and EDS) were used to study a welded joint, and microarray electrode (WBE) testing was added for the first time to study a welded joint. The corrosion behavior of each zone of a TA2 titanium alloy welded joint in flowing seawater and the overall corrosion tendency after coupling of three zones were studied at the macro- and submicroscales. Macroscopic results show that the HAZ and BM of a titanium alloy welded joint have better corrosion resistance in seawater. The microarray electrode shows that the WM is the main anode that accelerates corrosion, and at high flow rate, the electrode will change into the cathode. In conclusion, the data in this article provide a theoretical basis for the corrosion failure mechanism of TA2 welded joints.