2006 Volume 55 Issue 5 Pages 201-204
In order to prevent the damage of coating layer on marine structures by sea urchins, we studied the influence of coating hardness on the damage of anti-rust paint coating by a kind of sea urchins called ‘tawashiuni’ (Echinostrephus molaris). That is, we prepared steel test plates which have different coating hardness respectively, fed sea urchins on the test plates for three months and observed damage conditions of anti-rust coating layers. As a result, it was observed that coating damage reached base steel plate with regard to tar-epoxy-coating and epoxy-coating (Micro Vickers Hardness (MVH) after the tests were about 10 MVH and 18 MVH respectively.) and the rate of coating damage occurrence (ratio of the number of sea urchins which produced coating layer damage to the number of sea urchins observed.) was over 50%. On the other hand, in the case of epoxy-glass-flake paint which is the hardest coating among commercialized anti-corrosion paintings (MVH after the test was approximately 30) the occurrence rate of coating damage was 10% or so, and the damages were almost like scratches and did not reach base steel plate. Therefore it was considered that the coating layer damage, which reach base steel plate by ‘tawashiuni’, could be protected with epoxy-glass-flake paint although it is expensive. Further it was suggested that the coating layer damage by sea urchins hardly occur if MVH is not less than 40.
