Corrosion of coated aluminium alloy 7075-T6 galvanic test assemblies,part II: Impact of fastener through-hole condition

Abstract

The influence of the condition of through-holes on the corrosion of galvanic test assemblies was studied. Holes in coated aluminium alloy 7075-T6 were tested as received, in a worst-case bare condition and with extra protection. Regions away from fastener holes were also tested. Corrosion performance was assessed by electrochemical impedance spectroscopy in immersed conditions. Defects in the coatings at through-holes of as-received panels resulted in degraded corrosion performance, which could be mitigated by the application of additional protection. The presence of a fastener in the hole affected the corrosion performance for all three conditions even without galvanic coupling interactions. Galvanic interactions were studied on panels exposed to ASTM B117 salt fog conditions, where the through-hole condition also had a large effect.