<p>Under the high-temperature and high acidic environment in the acid regeneration process, the impeller of the turbine showed obvious corrosion failure. The corrosion failure mechanism of the impeller weld interface region was analyzed by optical microscopy, SEM, EDS, and XRD. It is found that turbine impeller was subjected to the synergistic effects of corrosion and erosion, at the same time internal voids were the origin point of corrosion. The effect of welding heat on the base material was analyzed by metallography, and the results were proved by microhardness tests. The thermal effect of the weld coarsens the base material grain and reduces its mechanical strength and corrosion resistance, while the acid mist flow accelerates the corrosion process, creating an erosion-corrosion cycle that leads to corrosion expansion along the weld area. The synergistic effect of properties degradation and external corrosion cycles ultimately led to failure of the TA9 alloy turbine impeller weld. The results of the study provide a reference for the reliability of the acid mist turbine during long-term service</p>