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Electrochemical impedance spectroscopy study on the corrosion of the weld zone of 3Cr steel welded joints in CO_2 environments

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International Journal of minerals,Metallurgy and Materials 2015年第5期22卷 500-508页

作者： Li-ning xu Jin-yang Zhu min-xu lu Lei Zhang Wei Chang Corrosion and Protection Center Key Laboratory for Environmental Fracture (MOE) Institute for Advanced Materials and Technology University of Science and Technology Beijing CNOOC Research Institute

The welded joints of 3Cr pipeline steel were fabricated with commercial welding wire using the gas tungsten arc welding （GTAW） technique. Potentiodynamic polarization curves, linear polarization resistance （LPR）, electrochemical impedance spectroscopy （EIS）, scan- ning electron microscopy （SEM）, and energy-dispersive spectrometry （EDS） were used to investigate the corrosion resistance and the growth of a corrosion film on the weld zone （WZ）. The changes in electrochemical characteristics of the film were obtained through fitting of the EIS data. The results showed that the average corrosion rate of the WZ in CO2 environments first increased, then fluctuated, and finally de- creased gradually. The formation of the film on the WZ was divided into three stages： dynamic adsorption, incomplete-coverage layer forma- tion, and integral layer formation.

关键词： petroleum pipelines steel corrosion welded joints carbon dioxide electrochemical impedance spectroscopy

Comparison Study on the Semiconductive and Dissolution Behaviour of 316L and Alloy 625 in Hydrochloric Acid Solution

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Acta Metallurgica Sinica(English Letters) 2020年第3期33卷 403-414页

作者： Zhu Wang Zi-Ru Zhang Lei Zhang Zhe Feng min-xu lu Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China

The corrosion behaviour of 316L and Alloy 625 was investigated using cyclic polarization,electrochemical impedance spectroscopy,X-ray photoelectron spectroscopy,Auger electron spectroscopy and induced coupled plasma-optical emis sion *** results indicated that Alloy 625 showed better corrosion resistance than 316L and the prolonging immersion time could enhance corrosion resistance of the two *** passive film formed on the surface of 316L exhibited an electronic structure of p-p heterojunction,with Fe3O4 and Cr2O3 enriched in the outer and inner layers,***,Alloy 625 presented the electronic structure of n-p heterojunction dominated by the outer Fe2O3/NiFe2O4 and inner *** resulted in the opposite semiconductive properties of the passive films formed on the two *** the acid solutions,Fe and Mo suffered from selective dissolution while Cr and Ni were relatively *** corrosion rates were mainly dominated by the dissolution of *** 625 presented better corrosion resistance than 316L due to the obviously lower content of Fe and the higher content of Cr and Ni in the passive *** continuously selective dissolution of iron resulted in the increase in Cr/Fe ratio in the passive film,which was responsible for the enhancement in corrosion resistance.

关键词： Stainless steel Induced coupled plasma(ICP) Polarization X-ray photoelectron spectroscopy(XPS) Passive films

Effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy steel and duplex stainless steel

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International Journal of minerals,Metallurgy and Materials 2012年第6期19卷 518-524页

作者： Jing Wang min-xu lu Lei Zhang Wei Chang Li-ning xu Li-hua Hu Institute for Advanced Materials and Technology University of Science and Technology Beijing Beijing 100083 China Research Institute of China National Offshore Oil Corporation Beijing 100027 China

To obtain high-quality dissimilar weld joints, the processes of metal inert gas （MIG） welding and tungsten inert gas （TIG） welding for duplex stainless steel （DSS） and low alloy steel were compared in this paper. The microstructure and corrosion morphology of dissimilar weld joints were observed by scanning electron microscopy （SEM）; the chemical compositions in different zones were detected by en- ergy-dispersive spectroscopy （EDS）; the mechanical properties were measured by microhardness test, tensile test, and impact test; the corro- sion behavior was evaluated by polarization curves. Obvious concentration gradients of Ni and Cr exist between the fusion boundary and the type II boundary, where the hardness is much higher. The impact toughness of weld metal by MIG welding is higher than that by TIG weld- ing. The corrosion current density of TIG weld metal is higher than that of MIG weld metal in a 3.5wt% NaC1 solution. Galvanic corrosion happens between low alloy steel and weld metal, revealing the weakness of low alloy steel in industrial service. The quality of joints pro- duced by MIG welding is better than that by TIG welding in mechanical performance and corrosion resistance. MIG welding with the filler metal ER2009 is the suitable welding process for dissimilar metals jointing between UNS $31803 duplex stainless steel and low alloy steel in practical application.

关键词： dissimilar metals welds stainless steel alloy steel microstructure mechanical properties corrosion

Influence of chromium on the initial corrosion behavior of low alloy steels in the CO_2–O_2–H_2S–SO_2 wet–dry corrosion environment of cargo oil tankers

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International Journal of minerals,Metallurgy and Materials 2015年第8期22卷 829-841页

作者： Qing-he Zhao Wei Liu Jie Zhao Dong Zhang Peng-cheng Liu min-xu lu Institute for Advanced Materials and Technology University of Science and Technology Beijing Marine Product Management Department China Classification Society Headquarters

The influence of Cr on the initial corrosion behavior of low-alloy steels exposed to a CO2–O2–H2S–SO2 wet–dry corrosion environment was investigated using weight-loss measurements, scanning electron microscopy, N2 adsorption tests, X-ray diffraction analysis, and electrochemical impedance spectroscopy. The results show that the corrosion rate increases with increasing Cr content in samples subjected to corrosion for 21 d. However, the rust grain size decreases, its specific surface area increases, and it becomes more compact and denser with increasing Cr content, which indicates the enhanced protectivity of the rust. The results of charge transfer resistance(Rct) calculations indicate that higher Cr contents can accelerate the corrosion during the first 7 d and promote the formation of the enhanced protective inner rust after 14 d; the formed protective inner rust is responsible for the greater corrosion resistance during long-term exposure.

关键词： low alloy steels corrosion rate chromium rust oil

Investigation of the deterioration of passive films in H_2S-containing solutions

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International Journal of minerals,Metallurgy and Materials 2017年第8期24卷 943-953页

作者： Zhu Wang Lei Zhang Xian Tang Zhao-yang Cui Jun-peng xue min-xu lu Institute of Advanced Materials and Technology University of Science and Technology Beijing Safetech Research Institute

The effect of H_2S on the corrosion behavior of 316 L stainless steel was investigated using electrochemical methods by changing the gas condition from CO_2 to H_2S and then back to CO_2. The presence of H_2S showed an acceleration effect on the corrosion of 316 L stainless steel in comparison with CO_2. The acceleration effect remained even after the complete removal of H_2S by CO_2, indicating that the passive film was irreversibly damaged. X-ray photoelectron spectroscopy(XPS) analysis indicated that the passive film was composed of Cr_2O_3, Fe_2O_3, and FeS_2 after being immersed in H_2S-containing solutions. The semiconducting property of the passive film was then investigated by using the Mott–Schottky approach. The presence of sulfides resulted in higher acceptor and donor densities and thus was responsible for the deterioration of passive films.

关键词： stainless steel passive films hydrogen sulfide corrosion

Effect of p H on the Electrochemical Behaviour and Passive FilmComposition of 316L Stainless Steel

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Acta Metallurgica Sinica(English Letters) 2019年第5期32卷 585-598页

作者： Zhu Wang Zi-Qiang Zhou Lei Zhang Jia-Yuan Hu Zi-Ru Zhang min-xu lu Institute for Advanced Materials and Technology University of Science and Technology Beijing State Grid Zhejiang Electric Power Research Institute

The effect of pH on the electrochemical behaviour and passive film composition of 316 L stainless steel in alkaline solutions was studied using electrochemical measurements and a surface analysis method. The critical pH of 12.5 was found for the conversion from pitting corrosion to the oxygen evolution reaction(OER). OER was kinetically faster than pitting corrosion when both reactions could occur, and OER could postpone pitting corrosion. This resulted in pitting being initiated during the reversing scan in the cyclic polarization at the critical pH. According to the X-ray photoelectron spectroscopy analysis, the content of Cr and Mo decreased with pH, while Fe content increased. This induced the degradation of the passive film, which resulted in the higher passive current densities under more alkaline conditions. The selective dissolution of Mo at high p H was found, which demonstrated that the addition of Mo in austenitic stainless steels might not be beneficial to the corrosion resistance of 316L in strong alkaline solutions.

关键词： Stainless steel pH Polarization XPS Passive films

Effect of Small Content of Chromium on Wet–Dry Acid Corrosion Behavior of Low Alloy Steel

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Acta Metallurgica Sinica(English Letters) 2017年第2期30卷 164-175页

作者： Qing-He Zhao Wei Liu Yi-Chun Zhu Bin-Li Zhang Shuan-Zhu Li min-xu lu Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China

Effect of small content of chromium（Cr） on wet–dry acid corrosion behavior of low alloy steels has been *** results show that the corrosion resistance of the steels increased with increasing Cr content from 0.10 to0.50 wt%.Higher content of Cr promotes initial corrosion and accelerates the formation of dense and protective rust in long-term *** enhanced protectiveness of the rust is closely related to its *** content of Cr increases the content of amorphous phases and decreases the content of c-Fe OOH in the rust,resulting in the high compactness of the rust and low electrochemical activity in acid *** dopes in rust and depresses the transformation from amorphous phases to a-Fe OOH,as well as the growth process of Fe OOH particles,which is responsible for the enhanced compactness of rust in long-term corrosion.

关键词： Low alloy steel Chromium Corrosion EIS TEM

Effects of W and Mo Additions on Wet-dry Acid Corrosion Behavior of Low-Alloy Steels Under Different O_2 Concentrations

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Acta Metallurgica Sinica(English Letters) 2016年第10期29卷 951-962页

作者： Qing-He Zhao Wei Liu Shuan-Zhu Li Bin-Li Zhang Yi-Chun Zhu min-xu lu Corrosion and Protection Center Institute for Advanced Materials and Technology University of Science and Technology Beijing

Effects of W and Mo additions on wet-dry acid corrosion behavior of low-alloy steels under different O2 concentrations were investigated. The results showed that W and Mo-containing steels presented excellent wet-dry cor- rosion resistance under O2 concentrations of both 1 and 5%. The roles of W and Mo played in increasing corrosion resistance of the steels were different. W could improve the thermodynamic stability of the steel substrate, while Mo could promote the formation of protective rust. Interaction between W, Mo and O2 concentration greatly influenced wet-dry acid corrosion of low-alloy steels. W addition was more effective for depressing charge transfer process at the rust/substrate interface and presented higher enhanced effect on increasing corrosion resistance than Mo under O2 concentration of 1%. Mo was more effective on increasing rust compactness and showed higher enhanced effect on increasing corrosion resistance than W under O2 concentration of 5%.

关键词： Wet-dry acid corrosion Steel Corrosion resistance Electrochemical impedance spectroscopy(EIS) Rust

Environmental boundary and formation mechanism of different types of H2S corrosion products on pipeline steel

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International Journal of minerals,Metallurgy and Materials 2017年第4期24卷 401-409页

作者： Lei Zhang Hui-xin Li Feng-xian Shi Jian-wei Yang Li-hua Hu min-xu lu Institute for Advanced Materials and Technology University of Science and Technology Beijing Beijing 100083 China Aircraft Engine Corporation of China Shanghai Commercial Aircraft Engine Manufacturing Co. Ltd. Shanghai 201306 China Shougang Research Institute of Technology Beijing 100043 China China National Offshore Oil Corporation Research Institute Beijing 100027 China

To establish an adequate thermodynamic model for the mechanism of formation of hydrogen sulfide (H2S) corrosion products, theoretical and experimental studies were combined in this work. The corrosion products of API X60 pipeline steel formed under different H2S corrosion conditions were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. A thermodynamic model was developed to clarify the environmental boundaries for the formation and transformation of different products. Presumably, a dividing line with a negative slope existed between mackinawite and pyrrhotite. Using experimental data presented in this study combined with previously published results, we validated the model to predict the formation of mackinawite and pyrrhotite on the basis of the laws of thermodynamics. The established relationship is expected to support the investigation of the H2S corrosion mechanism in the oil and gas industry. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

关键词： Energy dispersive spectroscopy Forecasting Gas industry Iron ores Pipelines Scanning electron microscopy Steel corrosion Steel pipe Thermodynamic properties Thermodynamics X ray diffraction X ray spectroscopy