Effect of grain orientation on the corrosion behavior of polycrystalline Alloy 690

Highlights: • The dissolution rate increases when the grain surface diverges to {1 1 1}. • The surface morphology changes when the grain surface diverges to {1 1 1}. • The grain surface further away from {1 1 1} has less easy dissolving area. - Abstract: The grain orientation dependent dissolution behavior of polycrystalline Alloy 690 in a solution of 0.1 M H2SO4 and 0.1 M NaCl was studied. Two complementary techniques of Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to reveal the grain orientation dependent dissolution rate and the surface morphology. The results show that Alloy 690 dissolves preferentially along the direction which has lower surface free energy. The grain surface with its normal vector further away from 〈1 1 1〉 has less easy dissolving area existing on its surface, which causes its much slower dissolution rate