Abstract
Cavitation corrosion in natural sea water has been induced on a copper–manganese–aluminium alloy used for marine propellers by means of a 20 kHz ultrasonic vibrator. The stirring effect of the ultrasonic probe on the free corrosion potential was investigated. A synergistic effect of cavitation and corrosion was found and attributed to microcracking and grain boundary corrosion which weakens the material and allows σ grains to become detached. The material was found to contain an active, brittle phase which is sensitive to both cavitation and corrosion. Corrosion current densities during applied polarisation scans were enhanced under the influence of cavitation because of the destruction of passivating films. Evidence was found for a work hardened layer.
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