From Microscale to Road Scale: Bridging the Gaps of Predictive Aluminum Corrosion Using SECM

Abstract

Aluminum (Al) corrosion starts off at the micron or even submicron scale and if it is coating protected, it occurs at the metal-coating interface. These corrosion events are by and large studied using bulk corrosion measurements making the understanding incomplete due to its micrometric scale occurrence. This gap is therefore targeted in current study by using a combination of SECM mapping modes together with a new strategy of employing redox-mediator mixtures. These combinations allow the exploration of both Al surface topographic features as well as corrosion hotspots. Nine differently finished AAxxxx surfaces (namely, AA5083-rolled-Zr, AA6061-rolled-Zr, AA6061-grinded-Zr, AA6111-rolled-Zr, AA6111-grinded-Zr, AA7075-grinded-Zr, AA7075-rolled-Zr, AA7075-rolled-ZnPh with sealer and AA7075-rolled-ZnPh without sealer) are investigated by SECM in their as-received state for corrosion and mapped on a 1 mm² scale with high precision. The most interesting outcome is that typically grinded samples show more cathodic current and a higher number of hotspots. The resultant SECM maps are then quantified to extract corrosion hotspots and correlate them with both bulk corrosion outcomes and the real-life corrosion road tests performed for 2 years. These investigations present a strong corrosion predictive strategy, which makes this study comprehensive and highly applicable to sectors like automobiles and aerospace) employing Al surfaces.