Persistence of Organotins 
A test to determine the life of an organotin in a seawater environ- 
ment was performed. A concrete panel made with TBTO-impregnated aggregate, 
cement, and water was prepared by Muraoka in May 1970, and placed in the 
harbor at Port Hueneme (Ref 4). In November 1977, it was removed from 
the harbor and cut with a concrete saw so that representative samples 
of both the interior and the outermost 3 mm were obtained. A portion of 
the sample from the interior was extracted three times with acetone and 
four times with benzene. Duplicates of these samples and a control 
which contained a known amount of TBTO were analyzed for tin by x-ray 
fluorescence spectroscopy. The analytical results were: 
Item Location ibsya, (GY) 
exterior WAV, 1285 
Exposed sample interior 1oS2, 1652 
interior (extracted) OR 2 Gr Ob) 
Control standard bo S5 bo BS) 
The standard was known to contain 14.8% tin, so the results should be 
raised about threefold. It will be seen, however, that the amount of 
tin found at the exterior of the specimen is nearly the same as that 
found at its interior. Furthermore, most of the tin present in the 
specimen was extractable in organic solvents; thus, it had not degraded 
to inorganic tin compounds during the 6-1/2 years the sample was in the 
ocean. It can be concluded that TBTO remains bound in an organic molecule 
for long periods of time in the antifouling concrete exposed in seawater. 
SUMMARY OF RESULTS 
Antifouling Properties 
Two systems employing toxicants as additives to concrete were found 
to have significant antifouling properties. The first of these employed 
porous aggregate impregnated with a mixture of bis-(tri-n-butyltin) 
oxide (TBTO) and creosote. The second employed triphenyltin hydroxide 
(TPTH), cuprous oxide, and methoxychlor, all of which were added to the 
concrete mix as dry powders. 
Both systems in which concrete was coated with toxicants exhibited 
good antifouling abilities. One consisted of a liquid organotin- 
polysiloxane coating brush-applied and allowed to cure by reaction with 
moisture in the air. With the second a sheet of rubber impregnated with 
TBTO was secured to the concrete by an adhesive. 
Toxicant Effects 
Compressive strength tests of concrete which contained antifoulant 
chemicals were also conducted. Results indicated that a sufficiently 
strong antifouling concrete could be prepared. 
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