CORROSION PROTECTION OF TIN-COATED LOW-CARBON STEEL WITH ELECTROLESS NI-P AS AN INTERLAYER

The corrosion protection of TiN-coated low carbon steel using electroless Ni-P as an interlayer was investigated by anodic polarization and a.c. impedance tests in a 3.5% NaCl solution. Both cathodic arc plasma and hollow cathode discharge methods were used to coat TiN in order to reveal the flexibility of this hybrid-coating process. Experimental results showed that the corrosion potential (E(corr)) and polarization resistance (R(p)) increased but the corrosion current (I(corr)) decreased as the Ni-P interlayer was introduced. The impedance of hybrid-coated specimens increased as a function of Ni-P layer thickness. The Ni-P layer with a lamellar structure acted as a serial connected resistor and changed TiN from a parallel connected resistor into a serial one. The corrosion resistance of TiN-coated low carbon steel was improved by introducing the Ni-P interlayer.