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Marine trial progress report
1980 - IRG/WP 453
In May 1977 and May 1978, tests of new chemical formulations for the protection of timber in the sea were installed in Mt. Maunganui Harbour. Investigation into new preservatives for such usage was urgently required since it had been found that there was progressive leaching of copper from copper-chrome-arsenate treated marine piles which could lead to a reduction in their service life. Hochmann (2) showed that few compounds exhibit the same toxicity to both Limnora and Teredo species. In the past it has been found that organotin compounds are among the more toxic chemicals to marine organisms. Representative chemicals of this type were therefore included in this test together with CCA retentions of 24 and 48 kg/m³ as standards from which performance of new formulations can be judged. Alternative inorganic formulations (acid copper chromate, copper silicate and ammoniacal copper arsenate) have also been included in this test. Since alkyl ammonium compounds (AAC) have been shown to exhibit some toxicity to marine borers, one of these compounds was included in the initial tests. To supplement the single formulation used in this series, copper salt-modified and alternate formulations of AACs were introduced for testing in May 1978. The treated stakes are being examined for resistance to both biological attack and leaching. In this report however, performance of the different treatments is rated by visual assessment and X-ray photographs of biological attack taken at sixmonthly intervals; chemical analyses to determine leaching rates have yet to be undertaken.
A F Preston, C M Chittenden