PREMATURE FAILURE OF REPAINTED EPOXY ON THE BOTTOM PLATE OF A MAIN FUEL OIL TANK - A CASE STUDY 1 M. Mobin and A.U. Malik Saline Water Desalination Research Institute Saline Water Conversion Corporation P.O. Box 8328, Al- Jubail 31951 Kingdom of Saudi Arabia Email: rdc@swcc.gov.sa ABSTRACT This article describes the premature failure of repainted epoxy coating applied over the inner side of the bottom plate of a fuel oil tank leading to perforation of the bottom. Some cavities and minute pits were already present on the inner surface of the plate when the coating was reapplied but the painters overlooked them. After about 2 months of service following repainting, penetration of the bottom plate of the tank occurred. The coating failure is attributed to chloride contamination of the steel surface prior to the coating application. INTRODUCTION Failures of coatings applied over the surfaces having soluble salt contaminations have occurred extensively. In general, the failures are in the form of blisters, rust, tubercles or loss of adhesion in areas where steel was previously exposed to corrosive condition. The cause of failure is generally attributed to the retention of minute amount of contaminant or corrosion product along grain boundaries of steel surfaces, even though blasted to white metal. The chloride contamination, which is most prevalent in marine environments, is the single most damaging anion because of its property to migrate under coating film. The chloride containing solutions have a high osmotic pressure contributing to moisture penetration, loss of adhesion and blistering. A number of studies concerning with the level of chloride contamination on clean steel surfaces and premature failure of coatings applied over such surfaces have been reported in the literature [1-5]. Various correlations between the level of chloride and 1 This Article published in the Journal “Materials Performance” in February 2005, 2, pp. 28-31.