Microelectrochemistry at heat-tinted zone of stainless steel weldment

摘要

Deterioration mechanism of corrosion resistance at heat-tinted zone of stainless steel weldment was studied. Local electrochemical measurements with micro capillary cell and surface analyses at small regions were conducted to correlate local variation in corrosion behavior and surface structure. Depletion of the Cr content at the substrate surface and formation of an Fe rich oxide layer on the surface were confirmed, although their distances from the welding bead were not identical. It was also revealed that the corrosion behaviors at the area with the Cr depletion and the area with the Fe rich oxide layer were different. The Cr depletion led to lowering of pitting potential due to the activation of substrate steel whereas the Fe rich oxide layer led to preferential rusting in the cyclic corrosion test due to deterioration of the surface protective layer.