Corrosion behavior of Zirconium R60702 weldment in 75 wt% sulfuric acid

Zirconium R60702 weldment was achieved by tungsten inert gas welding. Hot acid corrosion and electrochemical corrosion tests were performed on the specimens taken from the base metal (BM), the heat-affected zone (HAZ), and the weld zone (WZ) of the weldment in 75wt% sulfuric acid. Metallographic examination and X-ray diffraction (XRD) analysis showed that the impurity generating in the weldment during welding was zirconium dioxide. Cumulative mass loss test demonstrated that the BM exhibited good resistance to hot acid corrosion, the HAZ less, and the WZ least. Scanning electron microscope images illustrated that the corrosion mechanism of the BM was pitting whereas that of the WZ was inter-granular corrosion. In contrast, pitting and inter-granular coexisted in the HAZ. Anodic polarization and electrochemical impedance spectroscopy tests showed similar result to that of the hot acid corrosion test. In the electrochemical corrosion condition, the WZ had worse corrosion resistance than the other two parts. Therefore, the WZ is the key area of corrosion-resistance protection of the Zr R60702 weldment.