In order to clarify the mechanism of cathodic protection against cavitation erosion, cavitation erosion tests are carried out by using an electrostrictive vibratory apparatus. The cavitation aspects and the eroded surface are observed by means of high-speed and SEM photographies. The changes of relative gas content rate and nuclei size distribution are also measured under various cathodic currents. It is found that cavitation erosion is considerably suppressed by cathodic currents or tiny hydrogen bubbles, resulting in the remarkable decrease of mass loss. Such a suppression mechanism will be discussed from the viewpoint of hydrogen bubble clustering.
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