In ship's ballast tanks, most of coating failures (and corrosion attacks) were observed on sharp steel edge, welds seams and weld spatters. To achieve a proper coating film on sharp edges, application of a stripe coat using brushes or roller is often used, whereas alternative methods of mechanical grinding are also employed. This, however, requires high labor cost not to mention of the uncertainly of the final results. One of the possible approaches is to employ high solid coating material having less tendency to flow away from edges after application. With this approach, the need for smoothed edge is greatly reduces, and sometimes eliminated, with high solids coatings, thus reducing the cost and time invested in surface preparation. In this study, two coatings with different solid content are selected and evaluated in terms of their edge retention ability. In each coating the coating film thickness profile around the edge and solid content of coating materials were evaluated. The result suggested that the paint with lower surface tension as well as smaller surface tension differential during its curing stage, not the one with higher solid content would yield a better edge retention in the actual application. The current result clearly indicates that to achieve a proper edge coverage in painting applications, a proper selection of paint is, as important as to prepare proper edge roundness.
Keywords: water ballast tank, edge retention, high solids coatings, surface tension, solid content