The effects of zinc ions on the performance of epoxy coated mild steel under cathodic protection (CP)

This work aimed to address the issues that arise when cathodic protection is applied to a coated structure. The use of zinc chloride (ZnCl2) as a corrosion inhibitor was suggested; the idea was to bridge the weakly cross linked areas on the coating by depositing a film of zinc compounds in order to seal them from the corrosive environment.It was shown that the addition of 300 ppm ZnCl2 to 0.6 M KCl has an impact on the performance of the coating under the two different levels of potential that were used (−0.78 V and −1.1 V SCE) by maintaining the resistance of the coating above the border line between fair and poor coating for a period of 35 days; this was attributed to the deposition of zinc oxide (ZnO) at the base of the weakly cross linked areas.EDAX examination has confirmed the presence of zinc ions on the metal surface after immersion; this result was supported by the detection of ZnO using XRD technique.

► The effects of 300 ppm ZnCl2 on the performance of epoxy coated mild steel were investigated.
► Zinc compound was formed on the defected areas and seal them from the corrosive solution.
► The deposition of zinc oxide has improved the performance of the coating.
► The extent of corrosion was reduced on the coated specimens.
► The performance of the coating at −0.78 V was better than −1.1 V due to hydrogen evolution reaction at the latter.