EFFECTS OF SURFACE FINISHING METHODS ON CORROSIONRESISTANCE OF ALUMINIUM ALLOY

摘要

The effects of surface finishing methods on corrosion resistance of aluminium alloy wereinvestigated by polarization curve measurements using potentiometric methods. Specimens wereprepared using surface finishings mechanical polishing, chemical polishing and electropolishing. For themechanical polishing, specimens were ground with automatic grinding machine using silicon carbidepapers. The chemical polishing, specimens were first prepared by mechanical polishing with siliconcarbide papers 600 grit sizes and then immersed in an alkaline solution at 80 ℃ for 20 minutes. Theelectropolishing, the specimens were also prepared by mechanical polishing with silicon carbide papers600 grit sizes and then immersed in the same electrolyte as chemical polishing solution with appliedvoltage 15 volt for 20 minutes. All of the specimens were investigated by surface roughnessmeasurement, optical microscope, scanning electron microscope and potentiodynamic technique in 3.5wt.% NaCl solution. The results show that the surface finishing methods have strong influenced oncorrosion resistance and surface roughness of aluminium alloy. The roughness using mechanicalpolishing depends on the abrasive grit size. The small grit size provides smoothen and brighten on thealuminium surface. Chemical polishing gives valleys on the surface, which enhances chloride absorbtionon the surface and decreases corrosion resistance of the aluminium alloy. The electropolishing process ishighly efficient to remove scratches and forms a thin passive film on the surface, which enhances thecorrosion resistance of aluminium alloys in a better manner than mechanical polishing and chemicalpolishing.