Archive: To clean or not to clean
As the performance of antifouling systems in use is sometimes disappointing and the number of biocides approved is decreasing, the option to clean the hull is getting more and more into the focus.
Since years it is common practice to clean leisure boat hulls along the US-West coast. Frequently done by scuba-divers, they clean the hull of boats coated with biocidal antifouling paints as well as hulls with hard non-abrasive non-biocidal paints. The USEPA recommends to clean biocidal underwater coatings very softly to avoid the creation of a “plume of removed paint” entering the water body and increasing suddenly the concentration of copper and co-biocides in the water. In contrast, in the State of Washington you will pay a fine of 10,000 US$, if you clean a biocidal paint in water. In most European countries the cleaning of the hull in the water is prohibited and not a common practice. In-water cleaning of leisure boats became popular on so called non-biocidal eroding paints containing high percentages of zinc oxide, when they are fouled due to insufficient film thickness or insufficient activity of the boat(-owner). Cleaning of this type of underwater paint creates a large plume of colored water around the boat.
Under legislation of numerous countries in-water cleaning of hulls is problematic due to the fate of the fouling community removed, regarding its biological and chemical oxygen demand, incorporated pollutants and at least the introduction and survival of non-indigenous species.
Along with the necessity to collect the removed fouling organisms, the problem is unsolved to achieve extended cleaning intervals by using hard, non-toxic coatings which actually have to be cleaned every two weeks in saltwater. Research has to be intensified on this type of coating which can essentially reduce the adhesion of marine fouling organisms thus leading to cleaning intervals of 1 or even 2 months, in contrast to the necessity to clean on pure epoxy every two weeks.