IMO’s PSPC regulation adopted recently for ship’s water ballast tank specified the allowable NaCl limit to be 50 mg/m2 or less for primary and secondary surface preparation which shall be obtained by conductivity measurement in accordance with ISO 8502-6 & ISO 8502-9. However, the specified method provides the level of Total Soluble Salt (TSS) which is quite different from the amount of NaCl or chloride ion. Still, it has been specified to measure amount of NaCl on steel surface in IMO’s PSPC, which might be a source of dispute in world wide implementation of the PSPC for new shipbuilding.

In this study, extracted solutions by Bresle method from blasted or non-blasted blocks/steel plates were ion-analyzed for Cl-, NO3-, SO42-⁠, etc. for comparisons with TSS values. Ion Chromatography (IC) and Inductively Coupled Plasma (ICP) method, which measures specific ion concentration, were employed to measure exact amount of NaCl in the extracted water. The Cl- concentrations as determined by IC/ICP analysis were converted to surface NaCl by using molecular weight ratio.

The results revealed that actual content of NaCl was below 60- of TSS, which suggested that a certain compensation factor such as 0.6, should be incorporated in order to accept TSS as the NaCl in IMO’s PSPC.

Subject
Water, Ions, Contamination, Salts, Sodium chloride, Surface preparation, Sodium chloride solution, Ion concentrations, Surface analysis, Steel, Soluble salts, Elements, Conductivity
Keywords:
total soluble salt(TSS), blistering, NaCl, ion analysis, protective coating, shipbuilding
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2008
Association for Materials Protection and Performance (AMPP)
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