What materials should be used for the mechanical seal rings in highly corrosive media

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With the development of production, highly corrosive media are becoming increasingly common, placing higher demands on materials. Such as hydrofluoric acid, sulfuric acid and hydrochloric acid at various concentrations and temperatures, etc. Production cannot proceed without resolving the material issues. Here, two corrosion-resistant alloys are introduced: the nickel-molybdenum alloy 0Ni65Mo28Fe5V and the nickel-chromium-molybdenum alloy 00Cr16Ni60Mo17W4, which correspond respectively to the foreign Hastelloy B (Has·B) and Hastelloy C (Has·C). The former exhibits excellent corrosion resistance to hydrochloric acid, sulfuric acid, and phosphoric acid; it maintains high strength and dimensional stability at high temperatures, as well as good machinability. On the other hand, Hastelloy C is one of the most corrosion-resistant alloys in strongly corrosive oxidizing (or reducing) media. It remains highly resistant to hydrogen fluoride gas at various concentrations below 600°C, as well as to hydrogen fluoride gas at high temperatures. It also shows good corrosion resistance in nitric acid at various concentrations (except at its boiling point). It can be cast, forged, and welded, although it is difficult to machine. The biggest drawback of the above two corrosion-resistant alloys is their high cost. Their chemical composition and related properties are shown in Tables 10 and 11.