Electrochemical Corrosion Study of Cold-Rolled AA8015-Alloy Processed by Reversing Cold Rolling Mill at Varying Surface Roughness

Abstract

AA8015-alloy is a general-purpose aluminium alloy having a wide range of applications. Electrochemical corrosion testing of cold-rolled AA8015-alloy processed by reversing cold-rolling mill at different surface roughness in natural seawater were investigated. The AA8015-alloy utilised in this study was cold-rolled in a reversible Achenbach cold-rolling mill in four number of passes to a gauge thickness of 1.2 mm. This industrial cold rolling process was achieved at Tower Aluminium Rolling Mill, Sango-Ota, Nigeria. The different surface roughness’s each with three cold mounted samples, 1.54 μm, 0.83 μm, 0.18 μm and 0.04 μm were achieved on automated polishing machine using 320-grit, 800-grit, 1200-grit and diamond abrasive MD-Mol respectively. Electrochemical corrosion experiments were conducted on the samples in natural seawater using a computer-controlled potentiostat in an open polarisation cell set-up at room-temperature. The corrosion behaviour on surface morphologies of the samples was observed by high-mega-pixel camera and scanning electron microscope. Findings reveal asymmetric polarisation curves, and the polarisation resistance increases as the surface roughness decreases. Consequently, corrosion-rate reduces as the surface get smoother and EDS elemental analysis shows the existence of insoluble sulphate and chloride complexes formed on the surfaces. Conclusively, surface roughness affects the corrosion resistance of cold-rolled AA8015-alloy in natural seawater.