Study of corrosion mechanism occurring at cut edges of organically coated galvanised steels

The scanning vibrating electrode technique has been used to investigate the mechanism of corrosion occurring at exposed metallic cut edges of galvanis ed steel materials coated with organic polymeric layers of asymmetrical thi ckness. In the initial stages of corrosion a differential aeration corrosio n mechanism dominates. Anodic activity was focused on the zinc adjacent to the thicker organic coating and cathodic activity on the remainder of the e xposed metallic steel and zinc. Conventional corrosion testing methods have been used to highlight the importance of the differential aeration mechani sm for the initial stages of corrosion in such asymmetrically coated materi als. I&S/1451.