Etching of manganese aluminum bronze by ultrasound in seawater

Abstract

Manganese Aluminum Bronze (MAB), UNS designation C95700, is an alloy widely used for large marine propellers and other components in hydropower units. MAB has a complex microstructure due to precipitation of intermetallic phases as consequence of the cast process or thermal treatments. When investigating the marine corrosion behavior of MAB alloys, it was found that a metallographic etching attack occurred under the effect of ultrasound, similar to that observed with chemical reagents used for high-alloy bronzes. The main aim of this work is to compare the effects of etching on polished metallographic samples by ultrasound in seawater with that obtained with conventional chemical agents. It can be concluded that the effect of ultrasound is able to reveal, with great precision, the microstructure of MAB alloys, without the use of aggressive chemical agents, while the time under the influence of ultrasonic energy allows for fine-tuning the etching effect.