Test method of cavitation erosion for marine coatings with low hardness

Abstract

Rudders of large container ships are easily affected by cavitation, which is well known to be induced by significant axial flows behind a propeller and discontinuities in the rudder. Among several methods to prevent or reduce the cavitation erosion occurred in the rudder, painting is gaining a lot of attention because it can be employed easily and cheaply. To conduct erosion tests properly, the simulation of heavily erosive cavitation is necessary. This can be generated using an inclined propeller dynamometer in the medium-size cavitation tunnel of MOERI (Maritime & Ocean Engineering Research Institute). The inclined shaft of the propeller creates strong cavitation, which occurs around the root of the propeller blade. This cavitation creates impacts through the collapsing process that are very severe, and are useful for realistic and efficient cavitation erosion tests. In the present study, the newly developed cavitation erosion test method is successfully employed to evaluate marine coatings that is mainly composed of epoxy elastomer or silicone polymer material. Silicone polymer-type paint B was found to have three times larger endurance than epoxy elastomer-type paint A.