CORROSION BEHAVIOR OF ELECTROLESS NICKEL-PLATING MODIFIED TIN COATING

TiN films were prepared by reactive r.f. magnetron sputtering on low c arbon steel substrates. An electroless Ni-P plating was introduced as the interlayer in the modification of the TiN coating. The corrosion b ehaviour of the TiN coating assembly was evaluated using the salt spra y test and the polarization technique. For a thicker Ni-P interlayer ( greater than 5 mum), no appreciable corrosion was observed up to hundr eds of hours after salt spray testing. The polarization curve indicate s 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 i nterlayer modified TiN coating has better anticorrosion resistance tha n pure TiN coating on low carbon steel.