Corrosion resistance enhancement of Ni-P-nano SiO2 composite coatings on aluminum

In this study, the influences of different concentrations of SiO2 nano sized particles in the bath on deposition rate, surface morphology and corrosion behavior of Ni-P-SiO2 Composite coatings were investigated. The deposition rate of coating was influenced by incorporation of SiO2 particles. The microstructure was investigated with field emission scanning electron microscopy (FESEM). The amount of SiO2 was examined by Energy Dispersive Analysis of X-Ray (EDX) and amount of SiO2 nanoparticles co-deposited reached a maximum value at 4.5 % wt. Corrosion behavior of coated aluminum was evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques. The results illustrated that the corrosion rate decreases (6.5-0.6 mu A/cm(2)) and the corrosion potential increases (-0.64 to -0.3) with increasing the quantity of the SiO2 nanoparticles in the bath. Moreover, Ni-p-SiO2 nano-composite coating possesses less porosity than that in Ni-P coating, resulting in improving corrosion resistance. (C) 2014 Elsevier B.V. All rights reserved.