Abstract: Disclosed herein is a system for surface treating an internal surface of a part. The system comprises a tank within which the part is locatable. The system also comprises a fluid within the tank and capable of submersing the part when the part is located within the tank. The system further comprises a nozzle submersed in the fluid and configured to generate a stream of cavitated fluid directed in a first direction. The system additionally comprises a deflection tool submersed in the fluid and comprising a deflection surface that redirects the stream of cavitated fluid from the first direction to a second direction. The first direction is away from the internal surface of the part and the second direction is toward the internal surface of the part.