The facilities

In order to verify the effect of the high content of metallic ions in the slurry on the mechanism of erosion-corrosion of the target alloy, erosion pot tester is employed. Laboratory study is necessary because no experiments can be implemented in the field. The tester simulates the turbulent flow conditions expected at the pump’s propeller by generating a circular flow in a pot equipped with baffles. The test sample is located at the rotating shaft and connected electrically with an electrochemical set-up as shown in figure 2. The 2.2 kW three-phase motor with a maximum rotation speed of 24,000 rpm allows the generation of the desired flow, whereas a conventional three-electrode set-up allows for simultaneous electrochemical measurement at one of the samples.

The total weight loss of a metallic material, in this example low-alloy carbon steel, exposed to turbulent flow of slurry is explained by the mechanism of erosion-corrosion, involving both mechanical damage by the impinging particles and corrosive damage by the electrolyte. The two processes do influence each other, which is often referred to as synergy. Figure 3(a) shows the relative contributions of erosion, corrosion, and synergy of thereof to the total weight loss determined in the laboratory set-up. In order to explain the synergy in presence of metallic ions, a mechanistic model is proposed, in which the cementation of the more noble copper metal on the less noble surface of the steel is continuously interrupted by impinging particles – Figure 3(b).