Marine fouling is a major problem since humans engage in Marine activities, one of the thousands of years of struggle and Marine fouling organisms in the process of Marine antifouling technology is also in constant development and perfection, including coating containing organic tin antifouling agent (TBT) of antifouling paint application effect is by far the best and the most widely method. However, organotin compounds have been banned by the International Maritime Organization (IMO) since January 1, 2003 due to their high toxicity to the Marine environment.

SeaNine 211, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) being the biocidal ingredient, is a widely used antifouling agent to deter the undesirable biofouling phenomenon. It is commercially promoted as an environmentally acceptable antifoulant mainly due to its claimed rapid degradation in marine environment.

Rohm and Haas was the first company to obtain EPA registration for Sea-Nine 211 antifouling agent (EPA No. 64684-5) in 1994. At the time, it was the first registration of a new antifouling agent in nearly a decade, and the technology was awarded two major environmental awards: the Presidential Green Chemistry Challenge in 1996; 1997 Chemical Environment Award, known as the green antifouling agent.

Presidential Green Chemistry Challenge Award

Sea-Nine 211 is widely used in Marine antifouling paint, already has more than 20 years of practice method.finally, by antifouling paint with copper class distribution, can effectively prevent the "soft" sediment pollution, the hull comprehensive protection, provide protection for up to 5 years, figure 1 is a sailing ship after 21 months after, when the normal maintenance of entity photos, Apart from a very small amount of microbial contamination observed near the waterline, no Marine life was found attached to any other parts of the ship. Although the hull was designed for a sailing time of 18 months, after a sailing period of 21 months, the hull anti-fouling paint still has excellent anti-fouling performance.

Test Panels Immersed for Seven Months in Seawater 

   Not Coated with DCOI                Coated with DCOI       

Features of Marine antifouling agent SEA-NINE 211

  DCOI works by maintaining a hostile growing environment for marine organisms. When organisms attach to the hull (treated with DCOI), proteins at the point of attachment with the hull react with the DCOI.  This reaction with the DCOI prevents the use of these proteins for other metabolic processes. The organism thus detaches itself and searches for a more hospitable surface on which to grow. 

1, excellent antifouling performance

Marine attached organisms also known as Marine fouling organisms, is the growth in the bottom of the ship and all facilities in the sea surface of animals, plants and microorganisms, these organisms are generally harmful, its harmful effect known as biological fouling (also known as biological fouling bottom).

Algae are one of the main microorganisms responsible for "soft" deposition, and many aquatic and terrestrial algae can cause hull contamination. Mainly green algae, blue-green algae, diatoms, and brown algae. Barnacles are one of the main species of "hard" deposition, and there are many types of organisms in the world. Table 1 shows that Sea-Nine 211 has excellent killing effect on this kind of biological dirt.

2. Good biodegradability in seawater

The following figure compares the half-lives of SEA-NINE and TBT in Marine microecosystems composed of seawater and sediments.

In the Marine environment, SEA-NINE antifouling agents can be rapidly degraded, with a half-life of less than 1 hour. This means that only a very small amount of SEA-NINE will be present in the environment, so the harm to the environment is minimal. In contrast, TBT has a much longer half-life in the Marine environment than SEA-NINE. This is particularly evident in sediments, where TBT has been reported to have a half-life of six months to more than two years.

3, very low biological accumulation

The rapid biodegradation of DCOI is accompanied by rapid partitioning of DCOI to the soil/sediment.  This is in part due to the low solubility of DCOI in water.  The adsorption of DCOI by the soil/sediment further decreases its bioavailability.  In addition to the low bioavailability of DCOI it has a bioconcentration factor of only 13 as compared to 1500 for TBTO.1  Bioconcentration levels of 100 or more are generally considered to be of significance, thus bioconcentration of DCOI is not expected to reach levels in marine organisms that would lead to concern.

    In order to calculate the environmental risk of a substance scientists often consider the ratio of the predicted environmental concentration  (PEC) of a compound and the concentration of a compound in the environment at which predictions indicate there will be no effect on an organism(s) (predicted no-effect concentration, PNEC).  The ratio of the PEC/PNEC is know as

                                                                    RQ=PEC/PNEC

the risk quotient (RQ) and as the risk quotient gets smaller the less the risk there is associated with the substance.  Of course the RQ of a substance should be <1.  The RQ of DCOI ranges from .024 to .36 indicating that environmental concentrations of DCOI should pose little risk of toxicity to marine organisms. Conversely the range of RQ for organotin antifoulants is 15-430 indicating a significant risk to marine life.

4. Very low toxicity to Marine organisms

SEA-NINE metabolites are less than 1/100,000 as toxic as their parent, whereas TBT is about 1/50. Therefore, biodegradation can mitigate the toxicity of SEA-NINE, thus significantly reducing its environmental risk.

5. Environmental risk assessment

Experimental data indicate that the predicted environmental concentration of SEA-NINE is below its minimum chronic toxic concentration (risk quotient less than 1), indicating that its environmental impact is negligible. The risk quotient for TBT is much greater than one, indicating that it may have unacceptable environmental risks.