Anticorrosive Protection Effect of Zinc Coating on Ductile Cast Iron Pipes

Bitumen painted and zinc coated (130 g/m2) ductile cast iron pipe samples with damages were immersed in 5 g/L NaCl solution,the evolution of the electrochemical potential of the samples was measured periodically using electrochemical “two-electrodes” technique,and the time to first red rusting and the morphology evolution of the damaged area were recorded.The results indicate that the protective potential of iron is -0.780 V above which red rusting will appear.Compared to bitumen painting,zinc coating can provide cast iron pipes with effective cathodic and self-healing protection,thus delaying remarkably the time to first red rusting.