CORROSION RESISTANCE OF CHROMIUM-NICKEL STEELS IN PYROPHOSPHORIC ACID.

The equipment for producing pyrophosphoric acid is made, essentially, of corrosion-resistant grades 08Kh18N10T, 10Kh17N13M2T, and 06KhN28MDT steel. The feasibility of replacing 08Kh18N10T and 10Kh17N13M2T by the more available grades 08Kh22N6T aand 08Kh21N6M2T has also not been studied. Only within the stable-passive range are these steels corrosion resistant and may be recommended as a structural material for chemical apparatus. The stable-passive range widens upon an addition of molybdenum, more chromium, and copper to chromium-nickel steel. Nickel apparently does not have an appreciable effect here and, therefore, low-nickel grades of steel containing more chromium than grades 08Kh18N10T and 10Kh17N13M2T have wider range of passivity. Grades 08Kh22N6T and 08Kh21N6M2T may be regarded as fully equivalent in corrosion resistance in phosphoric acid, and thus as substitutes for grades 08Kh18N10T and 10Kh17N12M2T, respectively.