Tin content in ship hull coatings increased by 10 times
Oil industry magazine Bunkerspot reveals that the use of tin in hull coatings has increased by 10 times, despite the presence of an international ban:
“The use of organotin tributyltin (TBT) as an active biocide was banned about 10 years ago but industry professionals and environmentalists are now highlighting the increasing levels of TBT used as a catalyst in curing hull coatings.
Dr Rik Bruer, a former researcher at the Netherlands research institute TNO and now MD of Finsulate, a manufacturer of non-toxic antifouling wrap, commented on the re-emergence of TBT in marine hull coatings: ‘I have seen for myself that something strange happened with the formulation of these foul release coatings. Until 2002 I worked at TNO and at that time the chemistry of the silicone foul release coatings seemed to be in order. There was some organotin in there, but this is known to be a catalyst for curing these coatings.’
He continued: ‘About a year ago, I studied the Materials Safety Data Sheets of recent versions of these foul release coatings and it turns out that the amount of ‘catalyst’ added is more than ten times higher compared to 2005. ‘For me there is no debate that there is a purpose beside the catalyst activity and that the risk of spreading tin compounds against to kill marine life is eminent.’
The use of organotins in marine hull coatings was outlawed in 2008 with the ban on TBT but they can still be used as a catalyst if the organotin content does not exceed the allowable limit of 250mg/1kg of paint. Dibutyltin and dioctyltin are said to be the organotins most under scrutiny.
According to Professor Daniel Rittschof of Duke University in North Carolina, USA, ‘The effects of dibutyltin and probably dioctyltin are similar to TBT. Organotins at very low levels alter enzymes that process steroids, which is why molluscs change sex.’