Are TBT alternatives as good?

IMO has approved a draft Assembly resolution including a deadline of 2008 for the complete prohibition of organotins acting as biocides in antifouling.

Tributyltin (TBT) is one of the most effective organotin compounds used extensively in antifouling paint in recent years, but it has subsequently been proved that this compound, which leaches out of the paint slowly, remains in the water, harming the environment.

A draft resolution is to be submitted to the 21st IMO Assembly in November next year. It urges the Marine Environment Protection Committee (MEPC) to work towards a global legally-binding instrument ensure a global prohibition on the application of organotin compounds which act as biocides in antifouling systems on ships by January 1 2003, and a complete prohibition of these biocides in antifouling on ships by January 1, 2008.

The IMO`s plans to ban TBT in antifouling is worrying owners` organisations, such at the International Chamber of Shipping, because they believe that there has been unsufficient research carried out into the effects on the environment of the copper-based replacement paints.

Owners know from speaking to paint manufacturers that the copper-based replacements are not as effective as TBT, says Mr Joyce. Most vessels have a drydocking interval of five years, and although interim surveys are required every two – three years, these can be carried out in-water. If the maximum overcoating intervals quoted for the replacement paints are three years, this means ships need to be drydocked more often, involving extra costs, he says.