Advanced Materials Research Vols. 941-944

Abstract: In this study, low temperature plasma carburizing technology as one of the surface hardening techniques has been applied to improve the mechanical properties of 304 austenitic stainless steel. Several low temperature process parameters were studied to focus on the structure and properties of the carburized layer. The results shows that carburizing at 450°C, C3H8: H2 = 1: 40, carburizing time 10h could get a better white layer, a better wear resistance and a reasonable corrosion resistance, which proved to be the optimal hardening treatment.

Abstract: The pit corrosion behavior of steel rebar in alkaline chloride solutions without and with EMISE ionic liquids inhibitor were investigated by means of electrochemical noise (EN). The experimental results of electrochemical noise measurement revealed that the pit corrosion was inhibited and corrosion pitting process was retarded significantly. The mechanism of the inhibition effect of the inhibitor was analyzed based upon the combined stochastic theory and shot noise theory using the Weibull distribution and Gumbel distribution function.

Abstract: The corrosion property of high chromium cast iron was test under different phosphoric acid medium concentration. On the base of experimental data, the binary equation model of corrosion weight loss (W) versus phosphoric acid concentration and corrosion time (c, t) was built using multiple regression analysis, which can predict corrosion property of high chromium cast iron effectively. The prediction results show that the corrosion weight loss rises lineally with increasing corrosion time, and the corrosion rate rises quadratically with increasing phosphoric acid concentration. The corrosion failure mechanism is that chromium composite carbides (M7C3) stand out of matrixes surface after the matrixes composed of martensite and austenite are corroded firstly, then the M7C3 carbides drop out of matrixes when the matrixes can not wrap M7C3 carbides, resulting gradual corrosion of high chromium cast iron. The prediction values have sufficiently mined the basic domain knowledge of corrosion process of high chromium cast iron under phosphoric acid medium. Therefore, a new way of predicting corrosion property according to corrosion conditions was provided by the authors.

Abstract: With Visual Basic (VB) language programming, on the basis of traditional SSRT testing, and by the superimposition of square wave load with certain frequency, the stress corrosion test of tensile fluctuating load can be realized. SCC sensitivity of specimen superimposed with square wave load is weaker and its fracture is flat. Results show that VB language programming can accurately and effectively simulate the fluctuating stress state of pipeline caused by pressure fluctuation of natural gas in the stress corrosion test of materials, and can better study the rule and mechanism of stress corrosion of materials, so as to find the economic and effective protection method.

Abstract: In this study, composite metastable (Ti_0.5Al_0.5)N, (Ti_0.475Al_0.475Nb_0.05)N and (Ti_0.45Al_0.45Nb_0.1)N coatings were respectively deposited on a wrought martensite steel 1Cr11Ni2W2MoV by arc ion plating technique. All coatings possessed a dense structure, although droplets existed on the surface of the coatings. It was identified by XRD that the phase structure of all the coatings was the same B1 NaCl with a small mount of ε phase. Oxidation-resistance of (Ti,Al,Nb)N coatings at 800^oC for up to 50 hr was investigated and the results showed that the introduction of niobium into the coatings dramastically improved the oxidation-resistance of the coatings in air. (Ti_0.45Al_0.45Nb_0.1)N possessed more excellent oxidation-resistance than (Ti_0.475Al_0.475Nb_0.05)N.

Abstract: The recent years studies show, that almost all known building materials are exposed to biological damages, including artificial ones created by man, such as concrete. This largely substances. Currently, the aim of investigating the concrete biological stability in aggressive media and the research for effective ways to improve the biological resistance of concrete structures, are extremely important. In this work were studied the dependence of the concrete strength on the duration of exposure to different concentrations of sulfuric acid : 1-5% , 2-15% , 3-30 % , 4-50 % , 5-70 % , and also the dependence of the polymer mass content on the duration of storage in sulfuric different acid concentrations : 5.1 % , 2-15 % , 3-30 % , 4-50 % , 5-70 %. A method for determining the amount of reacted acid was proposed.

Abstract: By using the electrochemical methods of polarization curves and alternating-current impedance and drawing curves with Origin software as well as fitting and analyzing the data of the analytic experiments, the corrosion law of the carbon steel in stratum water containing CO₂ at different temperatures is researched in this paper. The result shows that the material corrosion in the simulated stratum water containing saturated CO₂ at different temperatures is active dissolution process and is mainly subjected to the activation control. The temperature rise increases the reaction rate of the reactant in the medium while promoting anode process and cathode process so as to increase the corrosion rate of the carbon steel. And, the auxo-action of the temperature to the cathode process is bigger than the anode process. The examples prove that the Origin software can conveniently draw the curves as well as rapidly and accurately analyze and fit the experiment data. The processing process is convenient and rapid, which can save much time than the manual calculation and works better than other professional mathematical analysis software because it does not need programming.

Abstract: The polarization curve and AC impedance are used to study the impacts of new corrosion inhibitor on the prestressed steel wire electrochemistry action in the simulated concrete pore solution. The result shows that, the ammonium molybdate, DETA, propylene thiourea, 1,4-butynediol and other compound corrosion inhibitors are positive inhibitory corrosion inhibitors, with the components of passivator and healant of protective oxide film, which can contribute to the formation of a passive film of oxide on the rebar surface, repair the defects of rebar surface, coat the entire rebar with a passive film of oxide with good compactness and stability, prevent the chloride ion from penetration, reduce the free rate of iron ions, and thus achieve the anti-corrosion purpose.

Abstract: The impact of local concrete crack on the prestressed steel stress corrosion sensitivity is studied with the SSRT, SEM and other methods. The result shows that, the local concrete crack will increase the prestressed steel stress corrosion sensitivity. The formation of stress corrosion microcracks on the metal surface below the crevice is based on two mechanisms: one is the pitting corrosion nucleation mechanism caused due to Cl^-, and the other is the non-pitting corrosion nucleation mechanism caused due to the film rupture. Once the initial stress corrosion microcrack is formed on the metal surface in the crevice, the interior of microcrack will be in the anodic polarization state due to the effect of the electric field of anodic polarization in the crevice, the metal in the crack will continue to be corroded, and the crack will expand. Moreover, due to the anodic dissolution reaction in the crack, the Fe (OH)₃ and Fe₂O₃ films will be formed on the side wall of the crack, and if the nonmetallic slag inclusions and other defects exist on the side wall of the crack, the origin of secondary crack will be formed here, and the intergranular secondary stress corrosion microcrack will be produced.

Abstract: The Pb–Ag–Ca alloy anode with surface passivation was applied in industrial production of zinc electrowinning. The application situation was investigated by detection and tracking more than 3 months. The results were analyzed by comparison with the data acquired from the production using the reference anodes without surface treatment. The results showed that using the anode with surface passivation can increase zinc yield, reduce Pb content in zinc product, prolong the anode life by improving the corrosion resistance, and then reduce the production costs.