Corrosion Behaviour of Nodular Cast Iron Used for Rotor Manufacturing in Different Wastewaters

Submersible drainage sump pumps work in a highly corrosive environment, forming films with reaction products on the surface. Pump rotors are high-demand parts, so they made of quality materials good wear and corrosion resistance properties such as nodular graphite cast iron. This paper analyses behaviour iron used manufacture three types wastewaters, variable pH. Nodular samples were immersed wastewater for 30, 60, 90 days tested by linear polarisation electrochemical impedance spectroscopy (EIS). Also, layers formed surface material analysed SEM EDS. The results showed that cast-iron acidic pH intense corrosion, oxide layer its is unstable. final structure product tri-layer cations anions absorbed from media: double-electric directly connected to metal surface, an internal consisting ferrous compounds ferric control diffusion oxygen, outer layer, compact crust compounds. change has major influence rate iron, which increases 356.4 µm/year DWW-1 (6.5 pH) 1440 DWW-2 (3 1743 DWWW-3 (11 respectively. As can be seen, experimental study covers problem pump rotor various wastewaters this aspect particularly important use predict possible deviations operation equipment within treatment plants.