Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by __________.

Correct Answer: Option A — cavitation

Cavitation occurs when local pressure drops below the fluid's vapor pressure, causing vapor bubbles to form. As these bubbles move into higher-pressure zones, they collapse violently against the impeller surface. This implosion removes metal, resulting in the characteristic pitted appearance often found on the suction side of impellers.