Corrosion behavior of 304 stainless steel in high temperature, hydrogenated water

Abstract

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-* h r -l h . X-ray photoelectron spectroscopy, in combination w i t h argon ion milling and target factor analysis, was appIied 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 ~io.zFeo.s)(Feo.ssCro.o5)204 on top of a chromite-based inner layer (Nio.zFeo.p)(Cro.7Fe~.~)~O4. These compositions agree closely with the solvi phases created by immiscibility in the Fe304-FeCr204 binary, implying that immiscibility plays an important role in the phase separation process.KEY WORDS : austenitic stainless steel, aqueous corrosion, hydrothermal reactions, X-ray photoelectron spectroscopy, high temperature water, Auger electron spectroscopy, type 304 stainless steel, corrosion oxide analysis, Argon ion sputter rate, spine1 oxides, target factor analysis.

Immiscibility in the NiFe2O4–NiCr2O4 spinel binary

“…0.2 vs. 0.1). This result is consistent with previous analyses [3,5] which indicate that the outer layer corrosion films on nickel base NiCrFe alloys contain a higher percentage of Cr(III) than those on stainless steels, i.e., n = 0. …”

“…Lattice parameters of the (cubic) spinel phases, determined from a whole pattern fit of XRD peak positions for five high angle reflection planes: [9,3,1], [8,4,4], [10,2,0], [9,5,1] and [10,2,2], are compared in Table I. Also included in Table I are the peak widths (full width at half maximum, FWHM) of the [8,4,4] peak.…”

Using Microscopy to Help with the Understanding of Degradation Mechanisms Observed in Materials of Pressurized Water Reactors

“…In the 1980s, working on stainless steels, Robertson [85] mentioned that the inner layer was Cr-enriched and consisted of a chromite spinel rather than chromine Cr 2 O 3 . These observations were detailed twenty year later by Ziemniak [86] showing that the inner layer was composed of a fcc spinel with a stochiometry close to (Ni 0. almost pure magnetite Fe 3 O 4 and more recently, Terachi [87] showed that they were AB 2 O 4 spinel (A and B = Fe, Cr and Ni). The effects of chromium and minor elements, cold-work, water chemistry and heat treatments rather than the oxidation mechanism itself were also studied [84,85].…”

Microstructural Characterization of SCC Crack Tip and Oxide Film for SUS 316 Stainless Steel in Simulated PWR Primary Water at 320.DEG.C.

“…Another way to clarify the mechanism underlying SCCby characterizing the oxide films formed on austenitic stainless steels has been carried out for many years, [10][11][12][13][14][15][16][17] because the chemical and physical properties of oxide films are thought to play important roles in the cracking process, especially in its initiation stage. [18][19][20] According to the results of those studies, oxide film formed on stainless steel in hightemperature water has a double-layer structure.…”