Abstract
Ni-Cu-P/nano-Al2O3composite coatings are prepared on mild steel from an alkaline electroless plating bath containing different concentrations of Al2O3nanoparticles. The protective effect of codeposited nanoparticles on the corrosion behaviour of the coatings is studied in 0.5 M H2SO4solution. The electrochemical methods, that is, electrochemical noise (ECN), electrochemical impedance spectroscopy (EIS), and polarization measurements, are used to characterize the corrosion properties of the coatings. The results show that the inclusion of nanosized particles leads to significant improvement of corrosion resistance of the coatings. The highest corrosion resistance is obtained at 20 ppm of nanoparticles concentration in the plating bath. The ECN measurements results are in good agreement with results obtained from two other electrochemical methods after trend removal. The SEM images prove that nano-Al2O3particles were embedded in the Ni-Cu-P matrix and are dispersed uniformly on the coating surface.
Highlights
Electroless nickel plating is an autocatalytic process which has found broad applications in industry due to attractive properties of resulting metal coatings, such as excellent corrosion protection properties, wear resistance, deposit uniformity, and solder ability [1,2,3,4,5]
The corrosion behaviour of coatings was studied by electrochemical impedance spectroscopy (EIS) technique in 0.5 M H2SO4
A conventional three-electrode cell was used for EIS studies which consists of an electroless plated sample as the working electrode, a saturated calomel electrode (SCE) as reference electrode, and a platinum rod as counter electrode [27]
Summary
Electroless nickel plating is an autocatalytic process which has found broad applications in industry due to attractive properties of resulting metal coatings, such as excellent corrosion protection properties, wear resistance, deposit uniformity, and solder ability [1,2,3,4,5]. Electroless Ni-P coatings can serve many roles, the search to improve coatings properties, such as hardness, antiwear, and corrosion protective performance, has led to getting incorporation of many solid particles in the matrix of the electroless Ni-P alloy coatings. In the presence of a little amount of copper, smoothness, brightness, ductility, and corrosion resistance of the electroless Ni-P deposit increase enormously [13, 14] Nanosized particles such as Al2O3 [15,16,17], WC [18], and TiO2 [19] are used to improve some surface properties of Ni-P electroless coatings such as wear resistance and hardness. The protective effect of nano-Al2O3 particles content on the corrosion behaviour of alloy coatings was studied using electrochemical methods including EN, EIS, and polarization measurements in the 0.5 M H2SO4
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