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Material degradation caused by wet hydrogen sulfide (Wet H2S) is one of the major issues in refineries. Carbon steel is the main construction material used in refineries and is subjected not only to thickness loss but the hydrogen is the major concern. H2S leads to high atomic hydrogen penetration in steel which causes degradation in the form of blistering and/or cracking (HIC/SOHIC) and stress cracking in the area of welds and heat affected zones. Mechanism is unusually dangerous due to high difficulty of threat assessment, which is mostly based on ultrasonic measurements or calculations based on the API standards. This research is based on evaluation of the real threat of wet H2S degradation based on examination of construction materials after 41 years of exploitation in refinery. The comparison of the theoretical calculation based on API standards and experience of the degradation of the real objects was characterized. Laboratory measurements include mechanical tests involving the elongation in the function of tensile stress and deformation, with analysis of material hardness and gas chromatography analysis. The results are complemented by studies of the chemical composition of the streams and analytical studies of the hydrogen content in the material obtained by the gas chromatography method. The tests showed compliance of the standard analysis of the corrosion risk with the laboratory tests performed on the real samples. Research leads to indication of the destructive methods which can be used on the materials obtained during scheduled material replacements or installation modernizations. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the applicability of Fe2O3/CeO2 nanoparticles for purification of aqueous media from manganese ions, by its absorption on the surface of nanoparticles, with further removal from the aqueous medium by magnetic separation. According to the data obtained, the structures under study are a mixture of two phases: the rhombohedral phase Fe2O3, which is characteristic of the hematite structure, and the hexagonal phase CeO2 with a phase ratio of 1:2. During corrosion tests, it was found that acid solutions with pH = 1 and 0.1% HCl, which varies from 0.0004 to 0.0007 nm/day, have the highest degradation rate and a decrease in the degree of ordering of the crystal structure of nanoparticles. Moreover, in the case of corrosion tests in PBS solutions, the degradation rate was 0.0002 nm/day. According to the data obtained, it was found that the absorption of manganese ions on the surface of nanoparticles leads to the formation of highly disordered or amorphous-like inclusions. In this case, an increase in the residence time in the medium leads to partial degradation of the nanoparticles, which leads to a decrease in the degree of purification. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to conduct the failure analysis of a water-supply system made from zinc-coated steel. The observed corrosion process had an intense and complex character. The brownish deposits and perforations were present after 2-3 years of exploitation. The electrochemical study based on the Tafel polarization, corrosion potential monitoring, and electrochemical impedance spectroscopy together with microscopic analysis via SEM and EDX were performed in order to identify the cause of such intense corrosion. The performed measurements allowed us to determine that thermal shock was the source of polarity-reversal phenomenon. This process had begun the corrosion of steel which later led to the formation of deposits and perforations in the pipes. The work includes appropriate action in order to efficiently identify the described corrosion threat. [ABSTRACT FROM AUTHOR]

This paper reports our scanning tunneling microscopy and spectroscopy (STM/STS) study of double-walled and multi-walled carbon nanotubes (CNTs) of different diameter deposited on Bi2Te3 (narrow gap semiconductor). The approximate diameter of the studied double-walled and multi-walled CNTs was 2 nm and 8 nm, respectively. Crystalline Bi2Te3 was used as a substrate to enhance the contrast between the CNTs and the substrate in the STS measurements performed to examine peculiarities of CNT morphology, such as junctions, ends or structural defects, in terms of their electronic structure. [ABSTRACT FROM AUTHOR]