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An Overview on Hydrogen Uptake, Diffusion and Transport Behavior of Ferritic Steel, and Its Susceptibility to Hydrogen Degradation
Development of high strength steel requires proper understanding of hydrogen behavior since the higher the steel strength the greater the susceptibility of hydrogen assisted cracking. This paper provides a brief but broad overview on hydrogen entry and transport behavior of high-strength ferritic steels. First of all, hydrogen absorption, diffusion and trapping mechanism of the steels are briefly introduced. Secondly, several experimental methods for analyzing the physical/chemical nature of hydrogen uptake and transport in the steels are reviewed. Among the methods, electrochemical permeation technique utilized widely for evaluating the hydrogen diffusion and trapping behavior in metals and alloys is mainly discussed. Moreover, a modified permeation technique accommodating the externally applied load and its application to a variety of steels are intensively explored. Indeed, successful utilization of the modified permeation technique equipped with a constant load testing device leads to significant academic progress on the hydrogen assisted cracking (HAC) phenomenon of the steels. In order to show how the external and/or residual stress affects mechanical instability of steel due to hydrogen ingress, the relationship among the microstructure, hydrogen permeation, and HAC susceptibility is briefly introduced.
KEYWORDs : ferritic steel, hydrogen uptake, hydrogen permeation, hydrogen assisted cracking
AUTHORs : Sung Jin Kim and Kyoo Young Kim†

Page : 201 - 208 DOWNLOAD
Effect of Lateral Diffusion on Hydrogen Permeation Measurement in Thick Steel Specimens
A finite element analysis is proposed to study the effect of specimen dimensions on lateral diffusion of hydrogen during hydrogen permeation flux measurements. The error of measurement on thick specimens because of 1D diffusion approximation may be as much as 70%. A critical condition for accurate measurements is to designate the area of hydrogen monitoring/exit surface smaller than the area of hydrogen charging/entry surface. For thin to medium thickness specimens (ratio of thickness to specimen radius of 5:10 and below), the charging surface should be maximized and the monitoring surface should be minimized. In case of relatively thick specimens (ratio of thickness to specimen radius above of 5:10), use of a hydrogen-diffusion barrier on the specimen boundaries is recommended. It would completely eliminate lateral losses of hydrogen, but cannot eliminate the deviation towards 2D diffusion near the side edges. In such a case, the charging surface should be maximized and the monitoring surface should be as closer in dimension as the charging surface. A regression analysis was carried out and an analytical relationship between the maximum measurement error and the specimen dimensions is proposed.
KEYWORDs : sour corrosion, hydrogen diffusion, HIC, blistering, permeation flux
AUTHORs : A. Traidia†, A. M. El-Sherik, H. Attar, and A. Enezi

Page : 194 - 200 DOWNLOAD
Detection of SCC by Electrochemical Noise and In-Situ 3-D Microscopy
Stress-corrosion cracking (SCC) of alloy 600 and alloy 800 in 0.5 mol/L thiosulfate solution during constant strain was investigated using electrochemical noise (EN) combined with 3-D microscope techniques. The in-situ morphology observation and EN results indicate that the SCC process could be divided into three stages: (1) passive film stabilization and growth, (2) crack initiation, (3) and crack growth. Power Spectral Density (PSD) and the probability distribution obtained from EN were used as the “fingerprint” to distinguish the different processes. During passive film stabilization and growth, the current noise signals resembled “white noise”: when the crack initiated, many transient peaks could be seen in the current noise and the
wavelet energy at low frequency as well as the noise resistance decreased. After crack propagation, the noise amplitudes increased, particularly the white noises at low and high frequencies (WL and WH) in the PSDs. Finally, the detection of metal structure corrosion in a simulated sea splash zone and pipeline corrosion in the atmosphere are established.
KEYWORDs : electrochemical noise, alloy 600, sensor, stress-corrosion cracking
AUTHORs : Da-Hai Xia, Yashar Behnamian, Jing-Li Luo†, and Stan Klimas

Page : 187 - 193 DOWNLOAD
The Influence of H+ and Cl- Ions on the Corrosion Inhibitive Effect of Poly(para-aminophenol) for Iron in Hydrochloric acid
Polymer amines are found to show distinct corrosion inhibition effects in acidic media. The functional groups of organic compounds have a wide role in the physical and chemical properties, for the inhibition efficiency with respect to steric factors, aromaticity, and electron density. The influence of H+ ions and Cl- ions on the corrosion inhibitive effect of poly(p-aminophenol) for iron in hydrochloric acid
was studied using electrochemical methods such as impedance, linear polarization, and Tafel polarization techniques. The experiments were conducted with and without the inhibitor, poly(p-aminophenol). The concentration range of H+ ions and Cl- ions are from 1 M to 0.05 M and 1 M to 0.1 M, respectively. With the inhibitor poly(p-aminophenol), this study shows that inhibition efficiency decreases with the
reduction of H+ ion and Cl- ion concentrations in aqueous solution. Further, it reveals that the adsorption of an inhibitor on the surface of iron is dependent on the concentrations of H+ and Cl- ions in the solution and the adsorption of inhibitor on the iron surface through the cationic form of amine.
KEYWORDs : poly(p-aminophenol) inhibition, corrosion, iron, H+ and Cl- ions, HCl
AUTHORs : P. Manivel †

Page : 183 - 186 DOWNLOAD
Galvanic Corrosion of Zn/Steel Couple in Aqueous MgCl2
Galvanic corrosion tests of Zn/steel couples were conducted in 1 M NaCl and 1 M MgCl2 solutions to investigate the impact of magnesium ion on corrosion behavior of the couples. Two types of Zn/steel couples were used for measurements of open circuit potential (OCP) and galvanic current. From the results of OCP transient of Zn/steel couples, the corrosion potential in 1 M MgCl2 was a more positive value than that in 1 M NaCl during the sacrificial dissolution of Zn. However, earlier increase of OCP of the couples in 1 M MgCl2 solution indicates that the sacrificial dissolution rate of Zn in 1 M MgCl2 was enhanced more than that in 1 M NaCl, agreeing with the results on transients of galvanic current. This result is due to that cathodic reaction on the steel surface of the Zn/steel couple was enhanced in 1 M MgCl2 by the occurrence of hydrogen evolution reaction.
KEYWORDs : zinc, steel, corrosion product, magnesium ion, galvanic current
AUTHORs : E. Tada†, S. Katakami, and A. Nishikata

Page : 175 - 182 DOWNLOAD
Influence of Carbon Fiber on Corrosion Behavior of Carbon Steel in Simulated Concrete Pore Solutions
Galvanic current measurement, polarization curves, electrochemical impedance spectroscopy and weight loss test were used to study the corrosion behavior of carbon steel before and after carbon fibers coupling to the carbon steel in simulated concrete pore solutions, and the film composition on the steel surface was analyzed using XPS method. The results indicate that passive film on steel surface had excellent protective property in pore solutions with different pH values (13.3, 12.5 and 11.6). After coupling with carbon fibers (the area ratio of carbon steel to carbon fiber was 12.31), charge transfer resistance Rct of the steel surface decreased and the Fe3+/Fe2+ value in passive film decreased. As a result, stability of the film decreased
and the corrosion rate of steel increased. Decreasing of the area ratio of steel to carbon fiber from 12.3 to 6.15 resulted in the decrease in Rct and the increase in corrosion rate. Especially in the pore solution with pH 11.6, the coupling leads the carbon steel to corrode easily.
KEYWORDs : simulated concrete pore solution, carbon steel, carbon fiber, galvanic corrosion
AUTHORs : Yuming Tang, Yuchao Dun, Guodong Zhang, Xuhui Zhao, and Yu Zuo†

Page : 167 - 174 DOWNLOAD
Inhibition of Rebar Corrosion by Carbonate and Molybdate Anions
Bicarbonate/carbonate and molybdate anions have been characterized for their inhibitive effect on pitting corrosion of carbon steel in simulated concrete pore solution by using electrochemical tests such as electrochemical impedance (EIS) and linear polarization (LP). It was revealed that bicarbonate/carbonate has a weak inhibitive effect on pitting corrosion that is approximately one order of magnitude lower compared to hydroxide. Molybdate is effective against pitting corrosion induced by the concentration of chloride as low as 113 mM and can increase the pitting potential of a previously pitted sample to the oxygen evolution potential by the concentration of molybdate as much as 14.6 mM only. The formation of a CaMoO4 film
on the surface hinders the reduction of dissolved oxygen on the steel surface, reducing corrosion potential
and increasing the safety margin between corrosion potential and pitting potential further. In addition,
pore-plugging by FeMoO4 as a type of salt film within pits increases the likelihood of repassivation.
KEYWORDs : steel, concrete, passivity, corrosion inhibitor, EIS
AUTHORs : Y. T. Tan†, S. L. Wijesinghe, and D. J. Blackwood

Page : 161 - 166 DOWNLOAD
Monitoring of the Content of Imidazoline-Containing Corrosion Inhibitor
The qualitative composition of active components of the corrosion inhibitor CGW-85567 was studied. It was found that С18:2 and С18:1 imidazolines and the corresponding imidazolin-amides are the major components. The HPLC/MS technique was developed for their determination in the water solutions of
monoethylene glycol (MEG). Industrial application of the inhibitor showed that MEG solution retained high concentration of the inhibitor for a long time after ceasing its addition into pipelines. Low values of the partition coefficients (0.010-0.014) of imidazolines in the system “water solution of MEG (concentration of MEG 62-85% v/v) - gas condensate” have allowed to pass on from the technology of continuous pumping of the inhibitor into protected pipelines to the periodic dosing technology. Taking into account a long time of circulation in the system and high temperatures during MEG regeneration process possible degradation products of the inhibitor were studied. N, N-dimethyl-dodecanamine-1, and N, N-dimethyl-tetradecanamine-1
were identified as major degradation products of the corrosion inhibitor CGW-85567.
KEYWORDs : corrosion inhibitor, imidazoline, HPLC/MS, tertiary amines, monoethylene glycol
AUTHORs : P. A. Zadorozhny†, S. V. Sukhoverkhov, A. N. Markin, K. I. Savin, and N. A. Prokuda

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