Safe level of chloride ions in wash water prior to epoxy coating on steel substrates for oil and gas storage/transmission

Quality of wash water for surface preparation of steel substrates prior to epoxy coatings is an important step in coatings industry. The level of chloride ions in wash water is one of the characteristics for better performance of epoxy coatings. Electrochemical Impedance Spectroscopy (EIS) was employed to study degradation behavior of polyamide epoxy coatings on mild steel. With and without water wash having varying levels of chloride ions. Coating Resistance (Rc), Open Circuit Potential (OCP) and phase shift (8) at higher frequencies were probed for characterization of coating performance upon exposure to accelerated conditions. A threshold level of chloride ions in wash water has been reported. (author)