Replacement of traditional seawater-soluble pigments by starch and hydrolytic enzymes in polishing antifouling coatings

Abstract

The use of starch and hydrolytic enzymes as replacement for traditional polishing pigments (e.g., Cu 2 O and ZnO) in antifouling coatings has been investigated. The enzymes facilitate a slow conversion of water-insoluble starch into water-soluble glucose, and dissolution of glucose causes the development of a leached (porous) layer in the wetted, outermost part of the coating. Subsequent water-binder interaction at the pore walls gives rise to polishing, in a manner similar to that of conventional antifouling coatings. Different starch types have been evaluated and classified as potential coating ingredients, and the impact of the addition of starch on the functional properties of the coating is described. Starches from rice, corn, and tapioca have been tested, and due to a smaller amount of water-soluble content and lesser tendency to agglomerate, corn starch is preferred. Leaching occurs in all the starch-enzyme coatings tested; however, polishing is only detected for two out of four binder systems investigated. Suitable polishing rates of 7-10 lm/month, based on the enzymatic starch-degradation, have been measured. Controls containing only starch (no enzyme) did not polish.

Copper release rate needed to inhibit fouling on the west coast of Sweden and control of copper release using zinc oxide

“…As a consequence, the release rate of copper increases (Hellio and Yebra 2009). Furthermore, particle size distribution also affects the rate of polishing, for example the polishing rate in TBT-based coatings has been shown to increase by decreasing particle sizes (Olsen et al 2010). The particle size of copper and zinc that was used in this study was on average 0.20 µm for the ZnO and 1.77 µm for the Cu2O.…”