Soluble Salt Criteria of Epoxy Coatings for Ship's Water Ballast Tank

Soluble salts left upon the substrate prior to coating application will cause premature coating failure at the coating/steel interface as well as underfilm corrosion of the steel substrate, especilly when the cencentration of the soluble salts exceeds a critical level. So, in order to prevent this salt-induced premature coating failure IMO's PSPC regulation adopted recently for ship's water ballast tank specifed the allowable NaCl limit to be 50mg/m² or less for primary and secondary surface prepartion. The finalized clause onthe issue, however, can be still subjected to argument mainly due to lack of reasonable technical data defining critical salt contamination criterion for coating system of ship's water ballast tank, which need to be verifed and discussed more. Also, the current technology still lacks full confidence regarding salt level determiantion under th filed condition. Therefore, in this study, coating performacne of epoxy coatings for ship's water ballast tank was evaluated with soluble salt levels, especially NaCl, via adhesion strength and blistering resistance test in immersion and condensation environment as well as reviewed some literature on blistering resistance of epoxy coating systems to propose reasonable soluble salt criterion for ship's water ballast tank