Abstract
This paper describes the effects of heat treatment and of SiC particle incorporation on the electrochemical behavior and physical structure of Niο£ΏP (17βat% P) composite coatings. The deposits were obtained by electrodeposition with various contents of SiC particles in the plating bath and heat treated at 420βΒ°C. The physical structure was investigated by inductively coupled plasma atomic emission spectrometry (ICPβAES), Xβray diffraction (XRD), and scanning electron microscopy (SEM β image analysis). The electrochemical behavior of the resultant composite coatings was determined by chronopotentiometry, electrochemical impedance spectroscopy, and potentiodynamic measurements in 0.6βM NaCl solution at pH 6. Heat treatment showed a positive effect on the electrochemical behavior of Niο£ΏP coatings, shifting the open circuit potential toward less active potentials. The incorporation of SiC particles inhibited pit nucleation on the Niο£ΏP composite coating, with or without postβheat treatment. However, heat treatment in the Niο£ΏPο£ΏSiC seemed to induce cracks in the metallic matrix, initiating at the SiC particles, possibly caused by the contraction in the metallic matrix. The cracked structure promoted localized corrosion, while coatings without heat treatment resulted in a general and uniform corrosion.