Injectable Sodium Bentonite Inhibitors for Corrosion under Insulation

Abstract

Corrosion under insulation (CUI) presents a significant threat to the safe and economical operation of insulated metallic structures. This paper explores the use of sodium bentonite to inhibit CUI via direct injection at the insulation-structure interface. Immersion tests were used to evaluate the inhibitor efficiency of sodium bentonite associated with carbon steel in both seawater and insulation leachate solutions over a range of temperatures typically encountered in oil and gas gathering lines. A novel design is proposed for an apparatus capable of injecting liquid-phase corrosion inhibitors along the insulation-structure interface where CUI occurs. Mass loss results indicate that for carbon steel at temperatures between 60°C and 82.2°C, sodium bentonite produces an average corrosion inhibitor efficiency of 50.9% in synthetic seawater and 52.9% in insulation leachate solution. Isopropyl alcohol was identified as a suitable carrier liquid for sodium bentonite CUI inhibitors intended for injection on steel structures insulated with closed-cell polymeric foams.