Analysis of localized corrosion mechanism of 2024 aluminum alloy at a simulated marine splash zone

The localized corrosion of 2024 aluminum alloy exposed to simulated marine splash zone is investigated by using electrochemical methods, surface and pit morphology analyses. The results indicate that 2024 aluminum alloy suffers severe pitting corrosion in the splash zone and undergoes severe pitting corrosion and intergranular corrosion in the full immersion zone. The inclusions act as cathodes and the surrounding matrix acts as anode which is dissolved. The capacitance arcs measured in the splash zone increases first and then decreases, due to the formation and erosion-induced falling off of the corrosion product. Compared with pits in the full immersion zone, the pits in the splash zone are not easy to propagate in depth, possibly because the pH value within the pits are higher than that in the full immersion zone, due to high oxygen content and water scouring in the splash zone. The lower sides of pits in the splash zone show a step-like change in depth compared with the upper sides, due to the laminar spalling caused by the joint action of water flow shear force and corrosion.