Corrosion Resistance of Electroless NiP/NiB Duplex Coating
Abstract— In present study, the morphology, structure and corrosion properties of electroless NiP/NiB duplex composite coatings on ferrous powder metal (PM) compacts were investigated. Some of the coated samples were heat treated at 400 °C for 1 hour. The morphology, structure and chemical composition of the coatings were analyzed by SEM, XRD and EDX. The corrosion resistance of PM compact and the coatings in 3.5% NaCl solution was assessed by polarization studies. The corrosion potential (Ecorr) and corrosion current density (icorr) were determined using the Tafel extrapolation method. The NiP/NiB duplex coating results in a significant increase in the corrosion resistance of the PM compacts. However, the applied heat treatment affects corrosion resistance of the coatings negatively.