Corrosion Resistance of Selected Cast Iron Grades Under Deposit Mining Conditions

Abstract

AbstractThe paper analyzes two types of alloyed cast iron used for pump impellers operated in mine working conditions. The research on corrosion resistance of two cast iron grades resistant to abrasive wear was presented. Tests were performed for chromium cast iron (HCCI) grade EN-GJN HV600 (XCr18) (acc. to EN 12513) and high-silicon cast iron HSCI Grade 1 (acc. to ASTM A 518/ A 518M - 99). Deposit mining is characterized by variable working conditions. Both types of cast iron are resistant to abrasive wear and are suitable for loaded elements (e.g. pump impellers). The paper presents a metallographic analysis of selected cast iron grades based on light microscopy. The chemical composition of the tested cast irons was determined with the Leco GDS 500 spectrometer; C and S content was determined with the CS125 Leco Carbon–Sulfur Determinator. The Si content for HSCI Grade 1 was determined by gravimetric method. Corrosion tests were performed under laboratory conditions. In-service tests of cast impellers were performed under real conditions (working mines applications). Corrosion resistance tests were measured with VoltaLab® Potentiostat (PGP 201). Performed tests resulted in the determination of the usefulness of materials used for dewatering pump impellers in mine working conditions. The results of laboratory tests were verified under the operating conditions of cast impellers. In the conditions of transporting a liquid-solid mixture at the moment of appearance of impurities (e.g. chlorine impurities) in the liquid, the impellers from cast iron HCCI revealed a tendency to pitting corrosion, which explains the exploitation results collected in the mining. After laboratory tests for sample from HCCI, the low value of breakdown potential Eb and repassivation Ecp was concluded which says about the absence of pitting corrosion resistance.