Pitting and galvanic corrosion behavior of stainless steel with weld in wet-dry environment containing CI −

Abstract

Accelerated corrosion test of stainless steel with weld was carried out to investigate the corrosion behavior under the wetdry cyclic condition in the atmosphere containing Cl −. In the surface morphology, corrosion products were analyzed by metallographic observation, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the damage to stainless steel with weld in the atmosphere containing Cl − is due to localized corrosion, especially pitting and galvanic corrosion. Weld acts as the anode, whereas matrix acts as the cathode in the corrosion process. The pitting corrosion, including the nucleation and growth of a stable pit, is promoted by the presence of wet-dry cycles, especially during the drying stage. Pits centralizing in weld are found to be grouped together like colonies, with a number of smaller pits surrounding a larger pit. The composition of the corrosion products is Fe 2O 3, Cr 2O 3, Fe 3O 4, NiCrO 4, etc.