Leaching of CCA from Bombax ceiba catamarans in operation for 15 years
V Kuppusamy, M Balaji, M V Rao, K S Rao
Core samples of wood at random were collected from all the timber pieces of each of the three catamarans made of CCA treated logs of Bombax ceiba put to continuous service for the last 15 years at the Lawson's Bay fishing village, Visakhapatnam. The samples were dried to constant weight, powdered, digested and analyzed for the residual salts of the preservative. The residual content of CCA was found to be 6.90, 6.24 and 7.43 kg/m3 in CAT I, II and III, respectively. The values for individual components of arsenic, copper and chrome were 0.24 to 0.34 kg/m3, 3.34 to 4.37 kg/m3 and 2.66 to 3.03 kg/m3, respectively. Making use of the initial absorptions of the preservative determined at the time of treatment and the residual contents estimated now, the leaching rates of CCA and it's components were calculated. While the annual leaching rate of CCA was observed to be 1.22 kg/m3 (CAT I), 0.81 kg/m3 (CAT II) and 0.83 kg/m3 (CAT III), at
elemental level, it was found to be 0.05, 0.04 and 0.05 kg/m3 in the case of arsenic, 0.15, 0.10 and 0.09 kg/m3 in the case of copper and 0.20, 0.12 and 0.14 kg/m3 in the case of chromium for CAT I, II and III, respectively. The results thus indicate that while about 2/3rd the initial amount of CCA had been leached out of the catamarans during the last 15 years, still 1/3rd the amount is present in the logs. Thus, the preservative left out in the catamarans appears to be sufficient to offer protection to the craft for a good number of years to come.