The resistance of cast iron to chemical and electrochemical corrosion depends on the exposure conditions, chemical composition and the distribution of alloying elements in the microstructure. The article presents an attempt to describe the formation of a corrosion layer under controlled chemical corrosion conditions for SiMo ductile iron. In the experiment, a (HT-HRD) chamber for heating the samples with a controlled atmosphere was used, at the same time providing the possibility of testing the sample surface using the XRD method. The analysis was both qualitative and quantitative. It allowed us to capture the sequence of the oxide layer growth on the tested samples. The beneficial effect of molybdenum on the corrosion resistance of SiMo cast iron has been proven. For all cases under analysis, the phenomenon of an increase in the share of hematite (Fe2O3) and magnetite (Fe3O4) was observed in the subsequent sample heating cycles. It turned out that the addition of molybdenum helps to create a tight oxide coating that inhibits the further growth of corrosion processes. Increasing the share of molybdenum in the alloy also reduces the thickness of the oxide layer.
Keywords: SiMo cast iron; corrosion; hematite; iron carbide; magnetite.