Corrosion resistance of AZ91 magnesium alloy with pulse electrodeposited Ni-SiC nanocomposite coating

Abstract

Magnesium and its alloys are the lightest of the structural metals, which makes them one of the most promising materials to minimize vehicle weight, but poor surface properties restrict the application of these alloys. In this paper, Ni-SiC nanocomposite coatings were applied on AZ91 magnesium alloy from Watts bath with SiC content 0 g.L-1 (pure Ni), 10 g.L-1 (Ni-10SiC) and 15 g.L-1 (Ni-15SiC) by application of pulse electrodeposition technique. The morphology and phase analysis were carried out by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) analysis, respectively. Micro-hardness of specimens was measured and the results revealed a significant enhancement: from 74 Vickers for bare AZ91 magnesium alloy to 523 Vickers for coated specimen in the bath containing 15 g.L-1 SiC. The Corrosion behavior of the samples was studied by potentiodaynamic polarization, and the obtained data showed the superior corrosion resistance for the coated AZ91 magnesium alloy, i.e. the corrosion current density decreased from 2.69 mA.cm-2, for the uncoated sample, to 0.00046 mA.cm-2, for coated specimen in the bath containing 15 g.L-1 SiC and the corrosion potential increased from -2.069 V to -0.33 V for the same conditions.