This work was aimed at explaining the corrosion mechanism of commercial Cr-Mn steels at 1073, 1173 and 1273 K in the atmospheres containing oxygen and sulfur. Three steels were selected for the investigations, two singlephase austenitic steels (Cr17Mn17 and Cr13Mn19SiCa) and a two-phase austenitic-ferritic steel Cr15Mn19. On all studied steels triplex scales were formed. The inner very thin, fine-grained part of the scale contained manganese, chromium and iron sulfides and oxides, the intermediate layer was built mainly of the MnCr 2 O 4 spinel while MnO was the predominant constituent of the outer scale layer. According to the gravimetric measurements, after an initial incubation period, the oxidation of steel follows a parabolic rate law. Thermodynamic and kinetic aspects of the formation of oxide-sulfide and oxide layers were discussed. Oxidation was accompanied by depletion of the subscale region of the metallic core in manganese, which is the austenite former. Consequently austenite transformed into ferrite.
The aim of this work was to study the deterioration of various kinds of sandstone due to acid rain and SO 2 gas. The samples were taken from three quarries in Poland and one sample was from a tomb about 100 years old. To elucidate the mechanism of stone deterioration, simple experiments were performed. The sandstone samples were immersed for several weeks in SO 2 aqueous solution of pH ≈ 4. Similar experiments were performed using SO 2 aqueous solution of pH ≈ 1.5. The concentrations of Ca, Mg and Fe leached from the sandstone samples were measured with TXRF. An additional experiment was carried out with the use of radioactive 35 SO 2 . The samples were exposed to both 35 SO 2 aqueous solution and to 35 SO 2 gas. The autoradiograms obtained from the sample cross-sections indicated that sulfur penetrated to the interior parts of sandstone samples, especially from SO 2 gas.
As a result of the oxidation of chromium (Cr)-manganese (Mn) steels, a multilayer scale is formed. The intermediate layer of this scale is composed of MnCr 2 O 4 spinel, and the outer layer is composed of MnO. The aim of the current study is to examine self-diffusion processes in MnCr 2 O 4 spinel by a tracer method. In experiments, the radioisotopes 54 Mn, 51 Cr, and 59 Fe were used. The serial sectioning method was applied for the simultaneous evaluation of diffusion rates of Cr, Mn, and iron (Fe) in MnCr 2 O 4 spinel at 1173 K under a pressure of 10 5 Pa in SO 2 containing 10 Pa O 2 . This spinel was obtained by a modified sol-gel method from metal nitrates (R. Gajerski and Z. Zurek, personal communication, 14.04.2004). It was found that the dominant mechanism of Mn transport in the studied samples is a volume diffusion, while Cr and Fe are transported mainly through the high-diffusivity paths.
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