Effect of pre-corrosion on the cavitation erosion performance of two aluminum bronzes in 3.5% NaCl solution

Abstract

The cavitation erosion (CE) behaviors of two aluminum bronzes after pre-corrosion in 3.5% NaCl solution were studied. Results indicated that the CE rate was increased by a factor of 82% for the nickel aluminum bronze (NAB) and 26.73% for the manganese aluminum bronze (MAB) after 30 days’ pre-immersion, compared with the results of the corresponding fresh sample without pre-corrosion. Mechanical impact was dominantly responsible for the CE damage of the pre-corroded samples. Pre-corrosion increased the E/T (the contribution of pure erosion to the CE-corrosion damage) value from 42.66% to 65.20% for the NAB and from 72.46% to 80.13% for the MAB. After pre-immersion, pits appeared at the eutectoid microstructure in the NAB and the network-shaped β phases in the MAB because of selective phase corrosion. This increased the surface roughness and weakened the surface mechanical property. Therefore, large and deep cavities and remarkable material loss were created due to the collapse of eutectoid microstructure in the NAB and the detachment of κ phases and brittle fracture of β phases in the MAB. The grievous CE damage of the MAB samples was highly attributed to the inferior mechanical property. In contrast, pre-corrosion had a much greater influence on the CE behavior of the NAB, because the CE resistance was remarkably deteriorated as a result of the corrosion damage at the eutectoid microstructure.