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Mechanism of high‐temperature sulphide corrosion of metals and alloys
Author(s) -
Mrowec St.
Publication year - 1980
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19800310508
Subject(s) - sulfidation , sulfide , sulfur , eutectic system , oxide , hydrogen sulfide , metal , high temperature corrosion , melting point , materials science , corrosion , metallurgy , ternary operation , inorganic chemistry , chemistry , alloy , composite material , computer science , programming language
Sulfidation appears to be considerably more suitable than oxidation for studying the high‐temperature behaviour of metals. Sulfide scales are formed at considerably higher rates and at lower temperatures, in addition it is much easier to work with the radioactive sulfide isotope. The experiments can be conducted in sulfur vapour or in hydrogen/hydrogen sulfide mixtures; differences are due only to different sulfur partial pressures. Sulfide scale is formed on pure metals (e. g. Cu, Ag, Ni) as well as in binary or ternary alloys. (e. g. FeNi, NiCr, CuZn, CoCr, FeCrAl) with consistantly reproducible results. Irrespective of scale thickness and structure the reaction rates are always controlled by outward diffusion with the high defect concentration favouring high reaction rates. Since various metals tend to form low melting metal/metal sulfide eutectics, it is necessary to keep temperatures below the particular melting point. Contrary to inner oxidation there is no inner sulfidation. The protective action of sulfide scale is considerably inferior to that of oxide scale. According to the results of the present compilation no material has become available which combines sufficient scaling resistance with good high‐temperature mechanical properties. Solution of this problem may perhaps be found by adding rare earth metals.