Comparisons of corrosion rates of Ni-P based composite coatings in HCl and NaCl solutions

The composite coatings of electroless Ni-P, Ni-P-PTFE, Ni-Cu-P and Ni-Cu-P-PTFE were prepared and their corrosion rates in HCl and NaCl solutions have been measured. The thickness and the compositions of the coatings were measured using a digital micrometer and an energy dispersive X-ray microanalysis (EDX), respectively. Surface morphology of the coatings was analysed by a scanning electron microscope (SEM). The incorporation of PTFE particles into Ni-P or Ni-Cu-P matrixes by gradually increasing the PTFE content from the substrate to the top surface improved the corrosion-resistant properties of the coatings significantly. The incorporation of copper into Ni-P or Ni-P-PTFE matrixes also improved the corrosion-resistant properties of the coatings. (c) 2004 Elsevier Ltd. All rights reserved.