Research for Replacement of Gray Cast Irons for Manufacturing Electrolyzer Gas Collection Bell Cast Components

Corrosion and failure of electrolytic cell cast components of a gas-collecting bell made of gray cast iron is due to oxidation of iron with oxygen, SO 2 gas, and sulfur vapor with formation of magnetite, hematite and pyrrhotite. As a result of iron oxide and sulfide formation scale is formed with a loose structure, which does not protect against interaction with a gaseous medium and does not prevent subsequent corrosion of electrolyzer gas collection bell cast iron components. Reducing the total length of interfacial boundaries within the cast material structure makes it possible to reduce the corrosion damage rate. This is achieved by modifying cast iron with magnesium to obtain spherical graphite inclusions. However, this modification method does not preclude full access of a corrosive gaseous medium to the electrolytic cell gas collection bell cast iron component working surface. A more effective way to protect electrolyzer gas-collecting bell cast component material from corrosion and destruction is alloying, which makes it possible to exclude precipitation of lamellar graphite within the cast iron structure. In addition, alloying elements may form surface oxide compounds that prevent corrosion initiation and development. For example, use of Cr makes it possible to obtain castings with good abrasion resistance due to presence of carbides within the cast iron structure, as well as to increase corrosion resistance due to alloying the metal base, and heat resistance due to an increase in metal base electrochemical potential and creation of a strong neutral oxide film on a casting surface. Comparative analysis of two cast irons showed that corrosion resistance of ChKh3 chromium cast iron is better than that of VCh50 nodular cast iron, and much better than that of lamellar graphite gray cast iron. However, ChKh3 chromium cast iron has poor casting properties, is very sensitive to cooling rate, and is heterogeneous in structure, which complicates casting technology in the manufacture of electrolyzer gas collection bell components.