A low-carbon steel A-36 and two conventional weathering steels A-588 and COR-420 exposed at four atmospheric test stations located in (i) Tocumen, an urban site near the Pacific Ocean, (ii) Sherman-Open, (iii) Sherman-Coastal, and (iv) Sherman-Breakwater on the Caribbean coast of Panama. Kinetics of the short-term atmospheric corrosion process and the relationship with exposure time and environmental characteristics of each site were investigated. The atmospheric exposure conditions, particularly the time of wetness, deposition of chloride, and the washing effect of contaminants on the metal surface by rain are of upmost importance in determining the corrosion behaviour and composition of rust. The corrosion products were mainly identified using room temperature and low temperature (80 K) Mössbauer spectroscopy, FTIR, and X-ray powder diffraction. In all samples, γ-FeOOH and α-FeOOH were the main constituents. Maghemite (γ-Fe 2 O 3 ), magnetite (Fe 3 O 4 ), and Akaganeite (β-FeOOH) were also identified.

Abstract:The synthesis of Mg doped Li2Fe1-xMgxSiO4 (x = 0, 0.10 and 0.15) via solid-state reaction is reported. The product was characterized by Mössbauer spectroscopy (MS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), magnetic measurements and scanning electron microscopy (SEM). The structures of the reaction products were confirmed to be the monoclinic structure P21/n, but impurities were detected in them. In the undoped sample small amounts of lithium iron oxide or lithiated magnetite was obtained, whereas a magnetic phase was found in samples with more than 10 % (mole fraction) of Mg doping.

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The mild carbon steel (CS) A-36 and weathering steel A-588 were exposed to the outdoor atmosphere at two different locations in tropical Panama. After a 10-year exposure, the results indicate that the chloride deposition rate and the type of steel play an important role in the corrosion behaviour of tested steels. Both types of steel mainly contain lepidocrocite and goethite as corrosion products at the urban site, while the corrosion products of steels exposed to a moderate marine atmosphere consisted of lepidocrocite, goethite and maghemite. The large fractions of maghemite in the corrosion products of steel A-36 suggest that this phase is interrelated to the higher corrosion rate of CS in the moderate atmospheric environment.