Water uptake of commercial antifouling coatings with binders based on trialkylsilyl acrylates or metal acrylates/ carboxylates

Erik Risberg, Anita Koop, Kari Dahl and Roar Hem, Jotun A/S, Norway

The emission of CO2, NOX and SOX from the shipping industry receives more and more attention as the world fleet is growing and the effects of global heating becomes more pronounced. A sufficiently effective antifouling coating, on the underwater hull, is crucial to minimize drag resistance and thereby emission to air. A clean hull will also be a very economic solution with constantly increasing fuel prices.

Self polishing copolymer (SPC) coatings are a frequently used group of antifouling coatings provided by all major paint suppliers. This technology is based on the reaction of the antifouling coating with seawater, which converts the polymer from an insoluble matrix to a slightly soluble one. A suitable and well defined polishing rate leads to a controlled release of the biocides present in the coating.

There are two main polymer technologies on the market today. These are based on trialkylsilyl acrylates and metal acrylates/ carboxylates. In the present work the water uptake of eight commercial antifouling coatings, based on these two technologies, has been investigated by gravimetrical measurements as well as Karl Fischer titrations. The water uptake and solubility of the binders isolated from five of these coatings were also investigated to further understand the correlation between the binders and the corresponding paints.