CORROSION BEHAVIOR OF ELECTROLESS NICKEL-PLATING MODIFIED TIN COATING

Abstract

TiN films were prepared by reactive r.f. magnetron sputtering on low carbon steel substrates. An electroless Ni-P plating was introduced as the interlayer in the modification of the TiN coating. The corrosion behaviour of the TiN coating assembly was evaluated using the salt spray test and the polarization technique. For a thicker Ni-P interlayer (greater than 5 mum), no appreciable corrosion was observed up to hundreds of hours after salt spray testing. The polarization curve indicates a barrier-type passive film in the TiN/Ni3P/Fe coating assembly. The corrosion currents for TiN/Fe, Ni3P/Fe and TiN/Ni3P/Fe are 200, 40-70 and 6-7 muA cm-2 respectively. It appears that the electroless Ni-P interlayer modified TiN coating has better anticorrosion resistance than pure TiN coating on low carbon steel.