CONSSO OCT 99/ 2/ NGO

Committee of North Sea Senior Officials

Oslo: 14 – 15 October 1999

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Ship Trials with Non-Toxic Antifouling Paints
on the German Coast

Presented by

World Wide Fund For Nature (WWF)

Background

- Reference is made to ED § 42 v) d)

„Ministers further AGREE to take concerted action within IMO in order ... to promote environmentally safe antifouling technologies.“

and ED Annex 3 § 1.3.2

„RECOGNISING the importance of a proper antifouling coating as an efficient means for limiting fuel oil consumption, i.e. emissions of greenhouse gases, the Ministers WILL PROMOTE research on the environmentally safe antifouling technologies and further AGREE to develop alternatives for protection and/or cleaning and agree to develop guidelines for sound dockyard practices; „

-CONSSO 98 agreed to urge North Sea states...to participate individually and jointly in the development of mechanisms to identify environmentally sound alternative systems (2.34).

-In response to continued argument that there are no effective alternatives to organotin antifoulants, the attached paper provides information on a pilot project from the German coast, demonstrating the engagement of ship owners and paint manufacturers involved in ship trials on the effectiveness of non-toxic antifouling paints. The project is now in its first year and future results will be presented to future meetings of CONSSO when available.

Action requested

-CONSSO is invited to take note of the information attachedand support the outlined efforts towards clean antifouling technologies. North Sea states are invited to, individually or jointly,call on the shipping industry to voluntarily replace organotin antifoulants with less toxic or non-toxic antifouling techniques before 2003, and ultimately aim towards eliminating use of all toxic antifoulants.

Ship trials with non-toxic antifouling paints on the German coast

1 Introduction

In autumn 1997 an initiative of WWF and the Ministries of the Environment in Lower Saxony, Schleswig-Holstein and Hamburg lead to three joint projects with several antifouling paint manufacturers. Against a background of severe contamination of the German coast by organotin compounds, an initiative was started for remediation of the coastal water bodies. The aim was to test non-toxic paints on ships operating along the German coast and to investigate their performance compared with controls of TBT and other conventional antifouling paints.

The initial project, conducted in Schleswig-Holstein, finished in February 1999, the project in Lower Saxony in April 1999, and the project in Hamburg will be finished in July 1999

Based on the final reports currently available, the results of the ship trials in Schleswig-Holstein and Lower Saxony are summarized and evaluated.

2 Project outline

The ships under investigation operated in the German Wadden Sea near to the coast and off-shore up to 100 nautical miles. The vessels stayed permanently in marine, brackish or freshwater or moved between these different waterbodies. Some vessels with flat bottom hulls had regular contact with the sea-bottom, others did not. The mean speed of the ships was recorded and varied between 5 kn, 10 -12 kn and 19 kn.

The following types of ships were used in the Lower Saxony project:

  • Coast Guard vessel, length 35 m, mean speed 12 kn, max. 19 kn, operating in the German Bight, North Sea;
  • Coast Guard vessel, length 17 m, mean speed 10 kn, max 15kn, operating in the Ems estuary;
  • two fishing boats of 15 -18 m length, mean speed 5 kn, operating in the Weser estuary and the North-Frisian Wadden Sea;
  • two passenger ferries of 25 m length, mean speed 10 kn, operating between the East-Frisian islands. The passenger ferries of the shipping lines Norden Frisia and AG Ems were invited to conduct the trials at no cost;
  • research vessel of 24 m length, mean speed 8 kn, operating in the East-Frisian Wadden Sea.

In Schleswig-Holstein two ships were used for the investigation:

  • a passenger ferry of the Wyker Dampfschiff-Reederei of 35 m length, mean speed of 12 kn, operating between the coast and several North-Frisian islands;
  • a passenger ferry of the Adler line with a length of 35 m, mean speed of 10 kn, operating between several North-Frisian islands and the coast. Both ship owners supported the project through the supply of their ships.

The ships were coated in the middle of the hull with 1 - 2m stripes -from water pass to chine on flat bottom hulled vessels or down to 2m for keel hull vessels -with non-toxic formulations and biocide containing antifouling paints as controls.

Paint manufacturers contributed to the project through the submission of free samples of test-paints. The application of the coatings was under the paint manufacturers' surveillance. The following paint companies participated in both projects:

  • CHUGOKU Germany, Hamburg;
  • HempelGermany, Pinneberg;
  • Akzo Nobel, International Farbenwerke Germany, Börnsen;
  • Relius Coatings, Hamburg;
  • SIGMA Coatings, Hamburg;
  • Tenax Marine Paints, Hamburg;
  • Wilckens Farben / Kansai, Glückstadt;
  • Witco, Bergkamen.

At regular and extra dockings the ships were coated with 3 to 7 seven stripes. Three types of coatings were applied in the tests :

  • biocide free, self-polishing coatings
  • biocide free, fouling release coatings, based on silicones. non-abrasive coatings in combination with special cleaning techniques like hydro-jetting, wiping with a sponge or brushing.

In total 12 biocide free formulations were tested and compared to 10 controls. Controls were conventional antifouling paints with either TBT, copper and/or organic biocides.

Two scientific institutions were in charge of the investigations: LimnoMar, Hamburg, and the Coastal Research Station of the Lower Saxony State Agency for Ecology, Norderney.

Inspections of the hulls were performed at the first docking before application of test paints and at roughly two month intervals. Inspections were made between February and November 1998 on ships in dockyards or lying dry at the shoreside at low tide. The main criteria measured at the inspections were:

  • degree of micro-and macrofouling in % area covered, measured in a frame of 75 x 75 cm (STG method);
  • determination of dominant fouling organisms;
  • dry weight of fouling;
  • measurement of the adhesion strength in shear force (ASTM method) of barnacles.

The evaluation criteria for the condition of the paint were:

  • damage of edge or panel
  • blistering, corrosion, peeling, chalking, eroding, checking, alligatoring

3 Results

Fouling release, silicone-based coatings

All tested silicon-based fouling release coatings had a fairly good to good effectiveness. Fouling could develop to a certain degree, but most of the organisms couldn't adhere strongly. As most of the ships under investigation were slow moving vessels, the area covered by micro-or small macrofouling organisms reached up to 80%, but fouling organisms could easily be removed by wiping with a sponge and/or hydroblasting with 1 bar pressure.

The fouling community peeled at intervals of 2 months inducing a variance of fouled area over the test period. On fast moving vessels like those of the Coast Guard, coverage with fouling was generally lower compared to slow moving ships. Mussels attached to minimal degree, roughly 0.5%. Only 10% of barnacles settled and fixed themselves effectively. These grew to a size of 5 -6 mm basal skeleton diameter at which point the exaggerated size created sufficient friction for the barnacles to be mostly removed by currents.

On all silicon-based coatings the adhesion force of barnacles was substantially reduced compared to surfaces such as epoxy-resins. The different silicones tested, showed a great variety in the adhesion force of barnacles. Values ranged from 2 kPa to 67 kPa betweeen the coatings. But variance of adhesion on one coating was remarkable as well.

Macroalgae grew slowly, as would be expected, and the mean length of thalli did not exceed 5 mm. Due to the absence of macrofouling, microalgae like diatoms covered extensive areas, but peeled themselves at intervals. All silicones, not exposed to strong mechanical forces, remained intact during the duration of the trials.

Self-polishing coatings

The self-polishing coating without biocides exhibited a very heterogenic performance from minimal fouled areas up to 100% coverage. On one of these coatings most of the barnacle larval spat could not attach strongly. Roughly one percent or less attached and grew up to larger individuals.

The adhesion force varied between 24 kPa and 142 kPa. The effectiveness of this type of coating correlated positively with the speed of the ship. Above 10 kn an evident increase in performance could be found. If fouling occurred, it consisted mostly of macroalgae which covered with long thalli up to 100% of test areas or small areas of a few percent were fouled with short algae, appearing like a biofilm.

Non-abrasive coatings

The Coast Guard vessel operating in the Ems estuary and the hull coated completely with a non-abrasive epoxy-resin had no macrofouling at all, and was covered with a film of diatoms and extremely minuscule forms of macroalgae. The fouling could easily be removed by hydroblasting with 50 bar. The nonabrasive coating on one sea-going ship failed and could not be sufficiently cleaned after the first four weeks of application.

4 Outlook and future perspectives

Encouraged by the fairly good performance of most of the coatings, three ships with stripes of good effectiveness shall be investigated for a further year. The aim is to test the coatings during bad weather and to obtain more information about the durability of fragile systems like silicones. More information shall be collected regarding costs of pretreatment, application, damage repair, paint removal, and overpainting. The fouling release coatings are known to require special procedures which have to be included in the evaluation of all relevant aspects.

Self-polishing or ablative coatings create no special problems in application or removal, but have to be improved in effectiveness. All coatings tested showed a better performance on faster moving ships compared to the slower ones. They need to be activated by currents, as they are based on a non-stick or weak adherence type of action. New products which act effectively on slow moving vessels will be tested in the future.

The ship of the Coastal Guard operating in the Ems estuary will continue with the anticorrosive paint and more ships operating in a similar manner will be coated with non-abrasive paints in the future

One ship will be coated with test stripes and another one will have the complete hull coated with new or improved products. Most of the shipowners and paint companies have agreed to continue with the trials. Furthermore, additional paint companies are joining the project with new types of coatings.

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