Corrossion Behavior of Ni-W-P Coating in Hypersaline Brine

Abstract

To improve the corrosion resistance of N80steel, Ni-W-P coating was prepared by electroless deposition. The corrosion properties for Ni-W-P coating were investigated in hypersaline ground brine. Results of weight loss tests show that the corrosion resistance of the Ni-W-P coating is 10 times of N80steel in hypersaline brine at 90 °C. Electrochemical tests show that the current density of Ni-WP coated sample reduce from 7.94×10 μA/cm to 4.28×10 μA/cm, and the corrosion potential changes from –0.700 V to –0.398 V compared with N80steel. Scanning electron microscopy (SEM) micrographs and X-ray photoelectron spectroscopy (XPS) were used to evaluate the morphology and composition of the corrosion layer of Ni-W-P coating. The results show that severe intergranular corrosion appear in N80steel, whereas no intergranular corrosion occur in NiW-P coating. The chemical composition of the corrosion layer of Ni-W-P coating is NiO,WO3, phosphate, and hypophosphite which led to superior corrosion resistance in hypersaline brine. This study confirms that the Ni-W-P coating can be applied for corrosion protection in hypersaline environment. Keywords-Ni-W-P coating; hypersaline brine; corrosion; corrosion resistance;corrosion layer;