The effects of different ionic migration on the performance of intact unpigmented epoxy coated mild steel under cathodic protection

The effects of the migration of sodium, calcium, and potassium ions through epoxy coated mild steel was investigated using electrochemical impedance spectroscopy (EIS), energy dispersive X-ray spectroscopy (EDAX), and visual inspection. It has been demonstrated that the application of cathodic protection (CP) has affected the protective properties of the coating in all immersion conditions. It has also demonstrated that CP application influenced water penetration, and the mobility of Na+, Ca2+, and K+ cations through the coating. The migration of these cations was shown to increase in the order Ca2+ < Na+ < K+. The deterioration of the coating was found to increase in the same order. A correlation was found between the mobility of the hydrated cations through the coating and the performance of the coating.

► The migration of Na+, Ca+2, and K+ through epoxy coated mild steel has been tested using EIS and EDAX.
► The migration of cations plays a significant role in the behaviour of the coated specimens.
► Coated specimens that tested in KCl were shown to have the least protective properties.