Corrosion behaviour of vacuum induction-melted Ni-based alloy in sulphuric acid

A vacuum induction-melted (VIM) Ni-based alloy was immersed in 60% H2SO4 solution to investigate its corrosion behaviour and resistance. The results indicate that the microstructure contains a γ-Ni solid solution + Ni3Si particles, dendrite Ni3Si, Ni3B, Cr7C3, and CrB. The corrosion started at the zones of the γ-Ni solid solution + Ni3Si particles and dendrite Ni3Si. These zones transformed to oxide films and protected the alloy from significant attack. However, the pitting corrosion created paths for acid solution and/or SO 4 2 - to further attack. Therefore, the corrosion rate decreased and then stabilised at a high value as the immersion time increased.