The end of TBT

The use of TBT (tributyltin) antifouling banned for use on leisure craft, but not commercially since the eighties, because of its harmful affects on marine life, finally looks like coming to the end of its days. Panama has at last signed the international treaty banning TBT on all its vessels worldwide,and as this brings the total merchant shipping tonnage having ratified the treaty to more than 50% of the world tonnage, it becomes automatic and enforceable by all states from July 2008. It has taken some twenty years for Britain to be in a position to enforce the no TBT rule, on say, tankers using the Solent.

It always seemed completely illogical that the most effective antifouling ever devised,could not be used on yachts whose combined bottoms were hardly equal to one of the many leviathans using our waters, while they were able to continue to use it with impunity.

 

Antifouling less effective in 2007?

Well I thought so. In the previous three seasons the boat has come out virtually clean,but this year I might just as well not have put any antifouling on at all. Launching at the end of April the bottom had a mat of well established stringy weed on the bow and around the stern particularly bad on the transom hung rudder, by the beginning of July. We scrubbed this off as best we could while afloat but by the beginning of August it was back with a vengeance. So out on the slip to clean off between tides and to apply a further coat of antifouling. Within a month the weed had noticeably returned and given another month’s growth to October, it looked to be anything up to 20cmlong.

So for the inquest involving a long discussion with the technical expert for the manufacturer,who assured me that I made the first mistake by only applying one coat at the beginning of the season, as two coats more than double the protection, in that if there is a thin spot the weed has a chance to get a foothold from where it will joyfully multiply. I have to say that it is my usual practice to give the bottom two coats, but this year having thoroughly removed the build up of old paint, I thought a second coat mid season would do the trick. He then told me that our cruising area, the Thames Estuary was particularly bad for fouling in 2007 and if I had been based, say, in the West Country there would not have been a problem. I may be doing him an injustice, but I have the feeling that had I been complaining about a boat kept in that part of the world it would have been the Thames Estuary where it was said to be most effective! Then we came to the crux of the matter; he told me that the paint manufacturers had faced unprecedented and mind-blowing increases in the cost of copper. They had the choice between doubling the price of the antifouling, which they did not consider the market would stand, or adding a new much more expensive product to their range. They chose to do the latter, so what I had assumed to be the same paint as I had used successfully before, was a very much weaker beast. He maintained that it was the amount of copper in the mix which was the important factor, and gave me a really good piece of advice, which I am happy to pass on. When you try to compare products the best test is to weigh the cans, the heaviest has the most copper and is the one to go for.

I put the matter to the test: the 5lt can of weak stuff which I certainly would not use again, weighs in at 6kg, while another can of commercial jollop which I stopped using as it was not self-eroding is some 2kg heavier. Next time you buy antifouling take some scales along; they may well help youmake abetter informed decision.

Finally when my boat was hauled out at the end of October, I wondered if I had been completely fair to the manufacturer, as while the fouling around the bow, stern and waterline was unacceptable, there was little elsewhere,and not a barnacle in sight. With a single exception the other boats which came out at the same time had considerably more fouling