Open AccessCorrosion Behavior of 304 Stainless Steel in High Temperature, Hydrogenated Water
Author(s) -
S.E. Ziemniak,
M. Hanson
Publication year - 2001
Language(s) - English
Resource type - Reports
DOI - 10.2172/821681
Subject(s) - materials science , corrosion , austenite , spinel , oxide , metallurgy , chromite , ferrite (magnet) , analytical chemistry (journal) , gravimetric analysis , x ray photoelectron spectroscopy , chromia , reaction rate constant , pitting corrosion , argon , kinetics , chemical engineering , microstructure , chemistry , composite material , physics , organic chemistry , quantum mechanics , engineering , chromatography
The corrosion behavior of an austenitic stainless steel (UNS S30400) has been characterized in a 10,000 hour test conducted in hydrogenated, ammoniated water at 260 C. The corrosion kinetics were observed to follow a parabolic rate dependency, the parabolic rate constant being determined by chemical descaling to be 1.16 mg dm{sup -2} hr{sup -1/2}. X-ray photoelectron spectroscopy, in combination with argon ion milling and target factor analysis, was applied to provide an independent estimate of the rate constant that agreed with the gravimetric result. Based on the distribution of the three oxidized alloying constituents (Fe, Cr, Ni) with respect to depth and elemental state, it was found that: (a) corrosion occurs in a non-selective manner, and (b) the corrosion film consists of two spinel oxide layers--a ferrite-based outer layer (Ni{sub 0.2}Fe{sub 0.8})(Fe{sub 0.95}Cr{sub 0.05}){sub 2}O{sub 4} on top of a chromite-based inner layer (Ni{sub 0.2}Fe{sub 0.8})(Cr{sub 0.7}Fe{sub 0.3}){sub 2}O{sub 4}. These compositions agree closely with the solvi phases created by immiscibility in the Fe{sub 3}O{sub 4}-FeCr{sub 2}O{sub 4} binary, implying that immiscibility plays an important role in the phase separation process