To understand the influences of corrosion test conditions on the corrosion behavior of suspension spring steels, we investigated the corrosion loss, shape of pits and structure of rusts at the conditions of wet-ratio 8%, 33%, 100% for SUP7 steel and UHS2000, the τmax=1300MPa-grade suspension spring steel. It was revealed that the corrosion was the most accelerated on wet-ratio 33%. Corrosion resistance was superior in UHS2000 which contains alloy elements such as Ni, Cr, Mo. Formation of amorphous rust was thought to give a big effect on the corrosion resistance, that is, corrosion resistance increased with increasing the fraction of amorphous rust. The amorphous rust was thought to act as a barrier against corrosive species. The reason that corrosion was accelerated on wet-ratio 33% can be explained that the amount of amorphous rust was minimum on that condition. And the reason that UHS2000 is superior in corrosion resistance can be explained by the fact that ratio of amorphous rust was much higher in UHS2000 than in SUP7.
