Adequate pretreatment of steel surface is essemial for performance of protective coating
system. Among many surface pretreatment methods, Sa 2.5 grade of "Near White Grit Blast Cleaning" is the most widely used. The downside of the grit blast cleaning is the complexity of the process, which limits the accessibility. As an alternative, power tooling has been increasingly used for surface treatment of marine vessels and offshore structures. It has been known, however, that the conventional power tooling provides less favorable result than the grit blasting.
In this study, several power tooling methods were evaluated regarding their effectiveness with
a purpose of finding the one capable of yielding the quality close to grit blast cleaning. Total of 4
different surface preparation processes (1 grit blast cleaning and 3 different power tooling) were
selected and each was evaluated in terms of resultant surface profile, subsequent coatings qualities including long term corrosion resistance, and other pros and cons. The results indicated that it was plausible to come up with a certain power tooling, capable of providing an almost equivalent to grit blasting.
Cleanliness of a substrate is essential to achieve proper adhesion. Any coating applied on the
substrate contaminated with rust, dirt, or oil cannot be expected to have appropriate bonding strength. Early coating failure may occur unless these contaminants were properly controlled within a certain range. Beside that, for better of adhesion of a coating, its substrate must have proper roughness as well, which produces an increased effective surface area for the mechanical bonding between a coating and its substrate. This roughness is also known as anchor pattern or surface profile, micro pattern of peaks and valleys on the surface. This anchor pattern can be obtained by a certain power-tooling method which cleans and roughens the surface, although it can be done as well by an abrasive blast cleaning, which is known to provide excellent formation of surface profile [ 1 ]. The downside of abrasive blast cleaning is, however, the complexity and heavy weight of the process equipment, which limits the accessibility to a complicated a huge marine structures. Therefore, as an alternative, the power tooling has been increasingly applied for the surface treatment for some areas of marine vessels and offshore structures such as welding joint line. It has been known, however, that the conventional power tooling method provides less favorable coating quality than the abrasive blasting method. Recently, new and innovative methods of power-tooling methods of surface preparation have been increasingly employed in shipbuilding and offshore industries in Korea. To evaluate the effectiveness of these new power tooling methods, in this study, total of 4 different surface preparation processes were selected and each was evaluated in terms of surface profile, coatings qualities including long term corrosion resistance, and other pros and cons.
