Fouling has been a well-known problem in the maritime industry for a long time. The most popular way of preventing fouling continues to be the use biocide-based antifouling paints. When it comes into contact with seawater, the paint releases toxic biocides which prevent marine growth. However, with biocides under the microscope, a new way of thinking is required. An initial step was the worldwide prohibition of antifouling coatings containing tributyltin (TBT) in 2008. The new EU biocide regulation was adopted in 2013, will set new standards. According to this regulation all biocide-based products must be approved before entering the European market.
Only those products, whose substances have been authorized, will be approved. Experts assume, that, when finally becoming valid in 2019, the EU regulation will cause an increasing demand for alternative antifouling coatings. RENOLIT is a family-owned business, a manufacturer of high-quality plastic films. The company developed a new product solving the problem of toxic antifouling coatings: the film RENOLIT DOLPHIN S. Based on the principle of fouling release, this film offers an alternative option to conventional paints.
The biocide-free RENOLIT DOLPHIN S is IMO-certified and thereby complies with the IMO AFS International Convention on the Harmful Anti-Fouling Systems on Ship (2001).
One of the film´s unique features is the ability to turn the ship’s hull into an amphiphilic surface. Studies have shown that there are certain types of barnacles which primarily adhere to hydrophobic surfaces and other types which adhere primarily to hydrophilic surfaces. Previous antifouling coatings based on silicone have only hydrophobic properties; Therefore, they would solely prevent the adhesion of the barnacles adhering on hydrophobic surfaces. The RENOLIT DOLPHIN S film combines these two properties and is thereby ‘amphiphilic’. Due to these attributes, marine organisms cannot entirely adhere to the ship’s hull and are simply washed off by the speed of the moving vessel (above 7 knots).
The Institute for Hygiene and Microbiology (formerly LimnoMar) is investigating the long-term effects of the films in direct comparison with other antifouling coatings since more than three years. In July 2015, a PVC plate was prepared with the RENOLIT DOLPHIN S and exposed in the Port of Norderney.
On the whole, 20 inspections have been carried out checking the films for any traces of barnacles, shells, algae or biofouling. The results are summed up in a so-called “Fouling Rating” (FR). On a scale from 1 to 100 (0 = full fouling; 100 = no fouling at all) the effectiveness of the film is rated.
The last inspection was conducted on 14 June 2018. After approximately 36 months by then, the RENOLIT DOLPHIN S shows only a small amount of barnacle seeds (1 percent) with a size of one millimeter. Apart from this, a slight biofilm (5 percent) is apparent. Overall, the film is rated with a FR of 98. A conventional silicon coating being tested in direct comparison, was rated with a FR of 96 after the same period of time. However, it shows barnacle fouling of barnacles (3 percent, size up to 6mm) as well as scratches (1 percent), barnacle imprint (2 percent) and flaking (1 percent) and a slight biofilm (5 percent).
In February 2016, the RENOLIT DOLPHIN S film was applied to the hull of the mooring boat Lütt Deern. In October 2017, it had to be taken out of the water for repair work. It provided the perfect opportunity to examine the special functionality of the film. At this year´s SMM, Benito di Racca, owner of the Lütt Deern and Managing Partner of H.S.H. Schleppgesellschaft mbH, shared his experiences with the film. ‘We use the film since more than two years and we never had problems. When the boat was taken out of the water, there was hardly any deposit build-up on the hull. No fouling, no shells. For me, this means that the film works.’ A further advantage of the film: A part of the film which was damaged in an accident in spring 2017 could easily be fixed with small film patches.
More informate: www.renolit-maritime.com
Reprinted with Permission from the November 2018 edition of Maritime Reporter & Engineering News - www.marinelink.com