Effect of Cerium Concentration on the Corrosion Resistance of Electro-Less Ni-P-PTFE Composite Coatings

Abstract

In order to improve the corrosion resistance of electro-less Ni-P-PTFE composite coating, electro-less Ni-P-PTFE composite coatings were prepared on 45# carbon steels specimen with addition of rare element cerium (Ce). Surface morphology of the coatings was observed by scanning electron microscope (SEM). Effect of cerium concentration on PTFE content of the coatings was investigated. The results indicated that properly added cerium into the bath increases the PTFE content of the coatings, decrease the corrosion rate, made the corrosion resistance improved of the coatings. And effect of cerium concentration on corrosion resistance of the composite coatings was evaluated by immersion test with 3.5% NaCl and 5% NaOH solutions respectively. With the rare element cerium concentration exceeding, the corrosion rate gradually increase. At the cerium concentration was 0.01 g.L-1, the corrosion rate of coating in the solutions were lowest, at 0.00186 mg·cm-2·h-1 and 0.00109 mg·cm-2· h-1. But with the cerium concentration go on increasing, the corrosion resistance of the coatings then decreases.