Studies on How Grooming Can Improve the Performance of Fouling Control Coatings
Foy, Lauren Elizabeth
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Biofouling is the accumulation of unwanted organisms on a submerged surface. This can be a major issue to most marine activities. The most common approach to biofouling prevention on ship hulls is the application of fouling control coatings (FCC), which can be categorized as biocidal and biocide-free. Grooming has been proposed as a proactive method to maintain these coatings and extend their working lives. In 2010, Tribou first defined grooming as the systematic, gentle, and mechanical disruption and removal of fouling on a ship hull. For biocidal coatings, grooming maintains the active biocide contained in the coating, preventing organism attachment. For biocide-free coatings, grooming applies a force that is great enough to remove organisms from the surface. This thesis investigated the interactions between fouling control coatings and different grooming brush designs. Two separate studies were undertaken to 1) study three different copper-based antifouling coatings, and 2) study biocide-free formulations (one commercial fouling release coating, and three biocide-free coatings). Each biocide-free coating type was groomed with three different brush designs to test varying forces imparted by each brush design. The purpose of the first study was to apply grooming on copper-based FCC at a copper output level sufficient to prevent fouling. In addition, the first study aims to reduce the environmental loading of copper into the water column with a lower copper content paint and reduced paint film thickness lost. The first study concluded that weekly grooming with a hybrid brush can maintain all three copper content formulations free of fouling. In addition, the highest-copper content by weight paint, BRA640 (37.1% copper by weight), released the most dissolved copper into the ambient water column. The paint with the moderate copper-by-weight percentage, 6400 (32.9% copper by weight), proved to release the least amount of dissolved copper into the water column while maintaining both paint thickness and a clean surface. The second study groomed the coatings with three different brush designs (bristle brush, hybrid brush, and stud brush) to determine which brush applied a force great enough to prevent fouling on the surface of biocide-free coatings. It was concluded that biweekly grooming with a hybrid brush significantly reduced fouling on the three experimental biocide free coatings and one commercial fouling release coating. Biweekly grooming with the stud brush, reducing fouling coverage, however damaged the surface of the coatings due to entrapment by hard fouling. It was found that biweekly grooming with the bristle brush removed biofilm, but failed to remove macrofouling.