Ending the use of antifouling paints on boat hulls?
Lauantai 19.6.2021 klo 14:58 - Mikko Nikinmaa
A significant problem with boat and ship hulls is that barnacles and algae attach to them especially in marine environment and, in addition to aesthetic problem cause both increased fuel consumption and decreased maximal speed. Because of these problems, antifouling paints have been used to prevent the growth of organisms on hulls. The problem with the organisms growing on hulls is that they are both animals and algae. Thus, to be effective, the antifouling paints must kill every type of organism.
Paints containing organic tin compounds, especially tributyltin, were used in hulls until it was found that the compounds cause imposex and loss of fertility in oysters in areas close to boat harbours. In addition to these toxic effects, they can cause various other toxic effect at environmentally occurring concentrations. Because of this, paints with these antifouling compounds are banned throughout the world today. Since tributyltin breaks down in a few weeks in pure, oxygenated water in the presence of sunlight, it was thought that toxicity of organic tin compounds would disappear in a year or maximally two of their ban. However, it has now become clear that their toxicity persists for tens of years. This is due to the fact that the compounds are quite stable in anaerobic sediments for tens of years, and become available to aquatic organisms whenever the sediments are dredged.
The organic tin-containing paints have been replaced with copper-containing paints often with booster biocides such as Irgarol 1051 and Diuron. In the paints copper has usually the valency of one. Cu+ is by far more toxic then Cu2+, and the toxicity caused to the aquatic environment is close to that of the organic tin-containing paints. Furthermore, the toxic copper compounds can persist even longer than the organic tin compounds. Consequently, one should be able to stop using the toxic paints altogether.One possible solution is attaching coating with miniature spikes on boat hulls. Such coating has been developed and has recently received a European Innovation Award. If and when the coating becomes a large-scale solution for antifouling in boat hulls, we may see the end of toxic antifouling paints altogether.