The relationships between impact energy of the particle and fracture volume which is the broken area multiplied by the film thickness are shown in Fig. 10 at an impact velocity of 70 ms−1. It can be recognized that the fracture volume linearly increased with the impact energy in logarithmic scale. The fracture volume in the more corrosive environment was larger than those in the other environments. On the other hand, the increase in fracture volume in wet air to the impact energy was significantly high. The linear curves depended upon the corrosive environments.