Synergistic effect of crevice corrosion and galvanic coupling on 304SS fasteners degradation in chloride environments

Abstract

Abstract The synergistic effect of crevice corrosion and galvanic coupling on the degradation of 304 stainless steel fasteners exposed to a chloride environment was investigated using electrochemical and surface analysis techniques. Results obtained revealed that the crevice region of the fastener showed lower corrosion resistance due to decreased surface passivation induced by the crevice geometry and low oxygen conditions, while the exposed region with a higher oxygen supply exhibited improved corrosion resistance. Coupling of the exposed and crevice regions of the fastener demonstrated accelerated corrosion attributable to galvanic effect. The driving force for the galvanic effect on the fastener was linked to three (3) key factors: (I) the potential difference established between the different regions on the fastener surface due to uneven oxygen distribution, (II) the difference in the solution environment, and (III) the difference in surface properties (active-passive surface). Morphological studies showed localised corrosion occurring mainly in the crevice.