Electroless Ni-P Plating of Carbon Steel via Hot Substrate Method and Comparison of Coating Properties with those for Co
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JMEPEG https://doi.org/10.1007/s11665-020-05286-8
Electroless Ni-P Plating of Carbon Steel via Hot Substrate Method and Comparison of Coating Properties with those for Conventional Method P. Verdi and S.M. Monirvaghefi Submitted: 13 December 2019 / Revised: 1 October 2020 / Accepted: 11 October 2020 In this study, Ni-P electroless coating was deposited on carbon steel by a new method called SLHS (substrate local heating system) which makes a higher rate of deposition possible without the risk of decomposition of electroless baths. The effects of pH and temperature on plating rate, composition, surface morphology, hardness and corrosion of the coating in SLHS condition (Tsub = 190 °C, Tbath = 80 °C) were investigated. In addition, the impact of heat-treatment at 400 °C for 1 h on hardness, morphology and microstructure was also studied. Samples prepared by this method were characterized by Scanning Electron Microscopy/Energy-Dispersive x-ray analysis, Light Microscope and x-ray diffraction. They were then submitted to Vickers microhardness and tribological tests. The deposition rates of electroless nickel (EN) coating were first estimated by weight gain method and then by light and scanning electron microscopy. Electrochemical Impedance Spectroscopy (EIS), Tafel polarization and salt spray tests were then used to evaluate the corrosion properties of the coatings. The study shows that maximum deposition rates for conventional and SLHS samples were approximately 20 lm/h and 32 lm/h, respectively. This increase in the plating rate reduces the phosphorus level by nearly 1.5 wt.% for SLHS sample. The corrosion resistance of SLHS sample is improved in comparison to the conventional one. Keywords
carbon steel, corrosion, electroless, heat treatment, hot substrate, nickel–phosphorus coating
1. Introduction Plating can generally be classified into two categories, namely electrical and chemical. The electroless process is a chemical coating technique in which there is a deposition of a metal, an alloy, or a composite on an activated surface by autocatalytic reduction of metallic ions from a salt solution containing a reducing agent (Ref 1). It is well known that electroless plating is an effective method for increased corrosion resistance and anti-wear properties of materials (Ref 2). Some of the advantages of using electroless coating are uniformity, excellent corrosion resistance, wear and abrasion resistance, solderability, high hardness, self-lubrication, increased hardness after heat-treatment, ability to plate irregular shapes and capability of depositing thin films of metal on nonconducting surfaces (e.g., glass, ceramics, polymers) (Ref 3). While there are many advantages to electroless plating, there
P. Verdi, Materials Engineering Group, Pardis College, Isfahan University of Technology, Isfahan 84156-83111, Iran; and S.M. Monirvaghefi, Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran. Contact e-mail: [email protected].
Journal of Materials Engineering and Performanc
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