Pretreatment-free Ni-P plating on magnesium alloy at low temperatures
(Applied Chemistry Department, University of Mohaghegh Ardabili, Ardabil, Iran)
Abstract: Electrochemically promoted electroless plating (EPEP) was used for the application of pretreatment-free Ni-P coating on AM60B magnesium alloy at low temperatures and the obtained coating was characterized by SEM, AFM, EDS and XRD techniques. Compact, uniform, and medium-phosphorus Ni-P coating with mixed crystalline-amorphous microstructure was obtained by applying a cathodic current density of 4 mA/cm2 at 50 °C. Also, island-like nickel clusters were deposited on the alloy surface under the same plating condition but without applying the cathodic current. In addition, the durability of the magnesium alloy against corrosion was strongly improved after plating via EPEP technique which was revealed by electrochemical examinations in 3.5% NaCl (mass fraction) corrosive electrolyte. The results of the electrochemical examinations were confirmed by microscopic observations. Thickness, microhardness, porosity and adhesive strength of the deposits were also qualified.
Key words: magnesium alloy; corrosion; low-temperature electroless plating; Ni-P coating