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In order to evaluate the effect of chromium content in carbon steel on the corrosion resistance of carbon steel materials, the corrosion behavior of 1Cr and N80 steels was investigated in this study by immersion weight loss method under three different CO2 partial pressure and temperature conditions in formation water for 72, 168 and 336 h. Detailed material surface morphological characterization was performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and confocal laser scanning microscopy (CLSM). The results show that the pitting corrosion of N80 carbon steel is serious at medium temperature and low CO2 partial pressure (50 °C, 0.30 MPa), and the corrosion rate is significantly higher than that of 1Cr steel. However, at high-temperature and high CO2 partial pressure (100 °C/0.63 MPa and 114 °C/0.73 MPa), 1Cr steel is more inclined to the mesa corrosion dominated by local corrosion characteristics, and the corrosion rate is seriously higher than that of N80 steel with uniform corrosion. From the experimental results, we can know the corrosion resistance of carbon steel and 1Cr steel is not only affected by the corrosion environment, but also depends on the formation process of the product film, as well as its compactness and integrity characteristics. At low-temperature and low CO2 partial pressure, 1 wt.% chromium content can provide a certain degree of corrosion resistance, while high temperature and high partial pressure can broaden the application window of carbon steel N80 and weaken the corrosion inhibition effect of chromium.

This paper aims to investigate the localized corrosion mechanism of Q125 casing steel in residual acid solution with Mannich base type inhibitors during oil reservoir acidizing process. The corrosion behavior of Q125 casing steel in fresh acid (20% HCl) and residual acid solution (pH 1.0 and pH 3.0 HCl) with and without 3-(4-chlorophenylimino)-1-(piperidine-1-ylmethyl) indolin-2-one (Mannich base type, Mb) inhibitor was studied by electrochemical test, weight loss, and surface analysis. The morphology and composition of corrosion products were analyzed by SEM/EDS and XPS; the local corrosion rate of casing steel with or without inhibitor was obtained by 3D profilometry. It was determined that the inhibitor had higher inhibition efficiency in fresh acid conditions than in residual acid conditions. Under the condition of residual acid, the decrease in inhibitor molecular coverage on the substrate surface promotes the occurrence of local corrosion. Pitting corrosion was detected in the residual acid solution containing Mannich base inhibitor, which may be related to the fact that FeCO3 hinders the adsorption of inhibitor molecules on the substrate surface.

Distributed Control System (DCS) has been widely recognized in the field of modern thermal power thermal control, and has significant effects in the application process. Today, the monitoring of electrical quantities is included into the DCS system, thus replacing the traditional "one to one" manual mode of operation in electrical control. It is to further improve the main works of the station automation and control systems. Combined with the actual project needs, this study focuses on the components of electrical control included in DCS system, the implementation of software and hardware features, and the measures to improve reliability. In addition, useful discussions have been made for some technical problems. In the DCS system, the electrical control inclusion is not just a perfection thermal power plant electrical control system, but a big improvement as well. In addition, it is a new attempt. At present, most of the electrical control parts of control system included into the DCS system with the manual operation are basically cancelled, but there are some problems, for example many of the designs do not match with the original operating habits, etc., which will have a certain impact on the tradition. In the transformation process of system, some of the designs are good but cannot be achieved currently. They still need further research and improvement, for example how can the electrical control of system enter into the DCS in a better manner, how can the display of light texts upon failure or abnormal time weaken electric signals in a more comprehensive and rapid manner, what are the new requirements for anti-interference, and other sequential control functions to be improved and perfected.