The corrosion behaviour and Rutherford backscattering analysis of palladium-implanted titanium

The corrosion behaviour of Pd-implanted Ti in boiling 1 M H2SO4 has been investigated by means of high resolution Rutherford backscattering (RBS) profiles of the Pd concentration as a function of corrosion time, and by electrochemical methods consisting of corrosion potential vs time curves and potentiostatic polarization data. Employing ion-implanted Xe as a surface 'marker', absolute corrosion rates were determined by RBS analysis and compared to corrosion rates determined from the polarization curves. The rate of Ti dissolution is found to be reduced by about three orders of magnitude for Pd-implanted samples. The corrosion potential-time curves and high resolution RBS data both show that soon after immersion, the Pd surface concentration rises to 20 at.% because of preferential dissolution of Ti and that the Pd is retained in the surface for corrosion times of up to 9 h. The steady state corrosion potential of implanted samples is close to that of pure Pd and 800 mV anodic with respect to the corrosion potential of pure Ti. The protection is explained by the fact that the mixed electrode potential is more noble than the critical potential for passivity of Ti, resulting in a markedly reduced dissolution rate. (author)