International Journal of Corrosion The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. An Investigation of a Combined Thiourea and Hexamethylenetetramine as Inhibitors for Corrosion of N80 in 15% HCl Solution: Electrochemical Experiments and Quantum Chemical Calculation Mon, 25 May 2015 14:07:49 +0000 The inhibition mechanism of thiourea (TU) and hexamethylenetetramine (HMTA) mixed in 15% HCl solution on N80 surface was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy measurements, and surface morphology analysis. Quantum chemical calculations and molecular dynamics simulations were performed to study the properties of TU and HMTA. The results showed that the inhibitors can form strong bonds and stable films on the surface, which inhibits the cathodic and anodic reactions in HCl solution and reduces the diffusion coefficients of corrosive particles. Jun Hu, Yun Wang, Lijun Yu, Yongqiang Zou, and Yuqi Wang Copyright © 2015 Jun Hu et al. All rights reserved. Eco-Friendly Corrosion Inhibition of Pipeline Steel Using Brassica oleracea Thu, 19 Feb 2015 06:26:59 +0000 The inhibition capacity of Brassica oleracea (BO) extract on the corrosion of pipeline steel in 0.5 M H2SO4 was evaluated using electrochemical techniques. The results showed an excellent inhibition efficiency which increased with initial increase in extract concentration and temperature to a point and decreased with further increase in BO extract concentration and temperature. Mixed inhibition behaviour was proposed for the action of BO. The unique behaviour of BO was attributed to the organic entities present in the extract. N. C. Ngobiri, E. E. Oguzie, Y. Li, L. Liu, N. C. Oforka, and O. Akaranta Copyright © 2015 N. C. Ngobiri et al. All rights reserved. Effect of Piperidin-4-ones on the Corrosion Inhibition of Mild Steel in 1 N H2SO4 Sun, 15 Feb 2015 14:32:03 +0000 The corrosion inhibition of mild steel in 1 N sulphuric acid solution by 2,6-diphenylpiperidin-4-ones with various substituents at 3- and 3,5-positions (01–06) has been tested by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopic methods, and FTIR and UV absorption spectra. The surface morphology of the mild steel specimen has been analyzed by SEM. The effect of temperature (300 to 323 ± 1 K) on the corrosion behavior of mild steel in the presence of the inhibitors (01–06) was studied using weight loss techniques. The effect of anions (Cl−, Br−, and I−) on the corrosion behavior of mild steel in the presence of the same inhibitors was also studied by weight loss method and the synergism parameters were calculated. The adsorption characteristics of the inhibitors have been determined from the results. Glory Tharial Xavier, Brindha Thirumalairaj, and Mallika Jaganathan Copyright © 2015 Glory Tharial Xavier et al. All rights reserved. Effects of Strain Energy and Grain Size on Corrosion Resistance of Ultrafine Grained Fe-20%Cr Steels with Extremely low C and N Fabricated by ECAP Tue, 06 Jan 2015 09:33:38 +0000 Effect of strain energy and grain size on corrosion resistance of ultrafine grained (UFG) Fe-20%Cr steels with extremely low C and N fabricated by equal channel angular pressing (ECAP) was investigated. UFG structures of initial grain size of 144 nm exhibited the typical three-stage softening comprising recovery, recrystallization, and grain growth. Potentiodynamic polarization measurements were carried out with a conventional three-electrode cell to evaluate pitting potential. Pitting potential in 1000 molm−3 NaCl solution was nobler in UFG state, but pitting potential started to decrease monotonously at lower temperature compared to hardness. The degradation of corrosion resistance in the early stage of annealing is attributed to stability change of passivation by recovery of dislocation structures inside grains and in nonequilibrium grain boundaries. We therefore conclude that nobler potentials of UFG states were realized by not only grain size reduction but also defective deformation-induced UFG. Muhammad Rifai, Hiroyuki Miyamoto, and Hiroshi Fujiwara Copyright © 2015 Muhammad Rifai et al. All rights reserved. Corrosion Potential Profile Simulation in a Tube under Cathodic Protection Thu, 18 Dec 2014 12:27:56 +0000 The potential distribution in tubes of a heat exchanger is simulated when applying cathodic polarization to its extremes. The comparison of two methods to achieve this goal is presented: a numeric solution based on boundary elements carried out with the commercial software Beasy-GID and a semianalytical method developed by the authors. The mathematical model, the simplifications considered, and the problem solving are shown. Since both approaches use polarization curves as a boundary condition, experimental polarization curves (voltage versus current density) were determined in the laboratory under flow conditions and cylindrical cell geometry. The results obtained suggest the impossibility of extending the protection along the whole tube length; therefore, other protection methods are considered. Mauricio Ohanian and Víctor Martínez-Luaces Copyright © 2014 Mauricio Ohanian and Víctor Martínez-Luaces. All rights reserved. Corrosion Inhibition Effect of 4-Hydroxy-N′-[(E)-(1H-indole-2-ylmethylidene)] Benzohydrazide on Mild Steel in Hydrochloric Acid Solution Thu, 11 Dec 2014 11:11:47 +0000 The inhibition performance and adsorption behaviour of 4-hydroxy-N′-[(E)-(1H-indole-2-ylmethylidene)] benzohydrazide (HIBH) on mild steel in 1 M HCl solution were tested by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The inhibition efficiency of HIBH increases with increase in inhibitor concentration in the temperature range 30–60°C. Polarisation curves indicate that HIBH is a mixed inhibitor, affecting both cathodic and anodic corrosion currents. The adsorption process of HIBH at the mild steel/hydrochloric acid solution interface obeyed Langmuir adsorption isotherm model and inhibition takes place by mixed adsorption, predominantly chemisorption. The activation and thermodynamic parameters for the corrosion inhibition process were calculated to elaborate the mechanism of corrosion inhibition. Preethi Kumari, Prakash Shetty, and Suma A. Rao Copyright © 2014 Preethi Kumari et al. All rights reserved. Electrochemical Investigation of Corrosion Behavior Heat Treated Al-6Si-0.5Mg-xCu (x = 0, 0.5, 1, 2, and 4 wt%) Alloys Sun, 07 Dec 2014 06:59:39 +0000 The corrosion behaviour of heat treated Al-6Si-0.5Mg-xCu (, 1, 2, and 4 wt%) alloys in 0.1 M NaCl solution was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The potentiodynamic polarization curves reveal that 2 wt% Cu (Alloy-4) and 4 wt% Cu (Alloy-5) content alloys are more prone to corrosion than the other alloys investigated. But the EIS test results showed that charge transfer resistance () increases with increasing Cu content into Al-6Si-0.5Mg. Maximum charge transfer resistance () is reported with the addition of 2 wt% Cu and minimum value is for 4 wt% Cu content Al-6Si-0.5Mg alloy. Due to additions of Cu into Al-6Si-0.5Mg alloy, the magnitudes of open circuit potential (OCP), corrosion potential (), and pitting corrosion potential () in NaCl solution were shifted to the more noble direction. A. Hossain, F. Gulshan, and A. S. W. Kurny Copyright © 2014 A. Hossain et al. All rights reserved. Exploratory Study of Sensitization in Cryogenically Cooled Ferritic Stainless Steel Welds Sun, 07 Dec 2014 00:10:13 +0000 Enhanced cooling via forced convection using cryogenic liquid is an option for controlling grain growth in the heat affected zone (HAZ) of ferritic stainless steel welds which improves joint strength. However, this technique seems to alter the martensite distribution in the high-temperature heat affected zone (HTHAZ) which is a critical constituent in rating the susceptibility to sensitization in ferritic stainless steel grades; any such information is not available in the literature. Thus, it is imperative to establish the influence of cryogenic cooling on sensitization dynamics in the HTHAZ. This paper discusses the influence of cryogenic cooling on sensitization in an AISI 430 ferritic stainless steel weld. It is established that cryogenic cooling increases the cooling rate in the HTHAZ and reduces the martensite volume percent by an average of 20%. This reduction in martensite content in the HTHAZ increases the level of ditched structure in cryogenically cooled welds and yields more ferrite-martensite ditched grain boundaries than in conventional welds. Although the cryotreated welds exhibit greater ditched boundary, the structure is still classified as nonsensitized, since no single grain boundary is completely surrounded by ditches. M. O. H. Amuda and S. Mridha Copyright © 2014 M. O. H. Amuda and S. Mridha. All rights reserved. Investigation on the Effect of Green Inhibitors for Corrosion Protection of Mild Steel in 1 M NaOH Solution Sun, 23 Nov 2014 09:26:36 +0000 Alkaline corrosion is one of the main issues faced by the industries. The main chemicals abundantly used in industries are NaOH, H3PO4, HCl, and H2SO4. Corrosion control of metals has technical, economical, environmental, and aesthetical importance. The use of inhibitors is one of the best options to protect metals and alloys against corrosion. The corrosion protection of mild steel in 1 M NaOH solution by mix of Henna/Zeolite powder was studied at different temperatures by weight loss technique. Adsorption, activation, and statistical studies were addressed in this work. Adsorption studies showed that inhibitor adsorbed on metal surface according to Langmuir isotherm. Surface studies were performed by using UV-spectra and SEM. The adsorption of inhibitor on the steel surface was found to obey Langmuir’s adsorption isotherm. The inhibition efficiency increased with increasing concentration of the inhibitor in NaOH medium. Inhibition mechanism is deduced from the concentration and temperature dependence of the inhibition efficiency, Langmuir’s adsorption isotherm, SEM, and UV spectroscopic results. Premjith Jayakumar Ramakrishnan, Vishnu Deth Kaleekal Janardhanan, Ramkumar Sreekumar, and Keerthy Parayil Mohan Copyright © 2014 Premjith Jayakumar Ramakrishnan et al. All rights reserved. Corrosion Effects on the Strength Properties of Steel Fibre Reinforced Concrete Containing Slag and Corrosion Inhibitor Mon, 17 Nov 2014 11:50:35 +0000 Corrosion in steel can be detrimental in any steel rebar reinforced concrete as well as in the case of steel fibre reinforced concrete. The process of corrosion occurring in steel fibre incorporated concrete subjected to corrosive environment was systematically evaluated in this study. Concrete specimens were prepared with steel fibre inclusions at 1.5% (volume fraction) of concrete and were added in slag based concrete (containing manufactured sand) and replaced with cement at 20%, 40%, and 60% of total binder. Accelerated corrosion studies were carried out using alternate wetting and drying cycle accompanied with initial stress at 40% and 60% of ultimate stress. Concrete specimens were then immersed in chloride-free water and sodium chloride solution (3.5%) after subjecting to initial stress. The alternate wetting and drying process of different concrete mixes was continued for longer exposure (6 months). Later, the strength degradation during the accelerated corrosion process was then assessed in compressive and flexural tests. Test results indicated that the strength degradation was marginal in the case of steel fibre reinforced concrete containing higher slag content and for the concretes containing corrosion inhibitors. The maximum strength reduction was noticed in the case of plain concrete containing steel fibres and, with the slag addition, a considerable reduction in corrosion potential was noticed. Also, with the increase in slag replacement up to 60%, a significant increase in strength was noticed in flexural test. Experimental test results also showed that the corrosion process in steel fibre reinforced concrete can be controlled with the incorporation of corrosion inhibitors in cementitious system. Sivakumar Anandan, Sounthararajan Vallarasu Manoharan, and Thirumurugan Sengottian Copyright © 2014 Sivakumar Anandan et al. All rights reserved. Electrochemical Impedance and Modelling Studies of the Corrosion of Three Commercial Stainless Steels in Molten Carbonate Thu, 06 Nov 2014 09:20:49 +0000 The corrosion induced by molten carbonates on the metallic structure materials is a problem constraining the life span of molten carbonate fuel cell (MCFC) at elevated temperatures. The reaction between the outgrowing oxide scale and lithium carbonate in the electrolyte is generally a slow process and very important to the passivation behaviour of the underlying steel. The corrosion behaviour of three commercial alloys (P92, SS304, and SS310) with different Cr contents in molten (0.62Li, 0.38K)2CO3 at 650°C was monitored by electrochemical impedance spectroscopy (EIS) for 120 hours to investigate the lithiation process. With SEM images and extensive XRD analysis of the oxides, equivalent circuits were proposed to interpret the impedance data and explain the corrosion behaviour of the three alloys at different stage with respect to lithiation process. C. S. Ni and L. Y. Lu Copyright © 2014 C. S. Ni and L. Y. Lu. All rights reserved. Electroless Deposition of Ni-Cu-P Coatings Containing Nano-Al2O3 Particles and Study of Its Corrosion Protective Behaviour in 0.5 M H2SO4 Wed, 05 Nov 2014 08:58:31 +0000 Ni-Cu-P/nano-Al2O3 composite coatings are prepared on mild steel from an alkaline electroless plating bath containing different concentrations of Al2O3 nanoparticles. The protective effect of codeposited nanoparticles on the corrosion behaviour of the coatings is studied in 0.5 M H2SO4 solution. The electrochemical methods, that is, electrochemical noise (ECN), electrochemical impedance spectroscopy (EIS), and polarization measurements, are used to characterize the corrosion properties of the coatings. The results show that the inclusion of nanosized particles leads to significant improvement of corrosion resistance of the coatings. The highest corrosion resistance is obtained at 20 ppm of nanoparticles concentration in the plating bath. The ECN measurements results are in good agreement with results obtained from two other electrochemical methods after trend removal. The SEM images prove that nano-Al2O3 particles were embedded in the Ni-Cu-P matrix and are dispersed uniformly on the coating surface. H. Ashassi-Sorkhabi, H. Aminikia, and R. Bagheri Copyright © 2014 H. Ashassi-Sorkhabi et al. All rights reserved. Study on Polymer Modified Cement-Based Coating with Healing Effect on Rusty Carbon Steel Tue, 30 Sep 2014 11:35:44 +0000 The anticorrosion properties of polymer emulsion modified cement-based coating with healing effect on carbon steel were investigated. The change of linear polarization resistance () and electrochemical impedance spectroscopy (EIS) have been used to measure the inhibitive and curative effect of electrodes painted with the coating in 3.5% NaCl solution. The results indicated the high alkalinity of filler (cement) in coating can obviously improve the anticorrosion performance of coated steel electrodes. And the inhibitive ability of cement-based coating with fluoride acrylic emulsion is superior to that of the coating with epoxy emulsion. Moreover, by adding antirust pigments and rust converters in the fluoride acrylic emulsion modified cement-based coating, the inhibitive property was improved and the curative effect can be observed. Kunrong Wang, Zhiyong Liu, Zixiao Wang, and Weibin Yang Copyright © 2014 Kunrong Wang et al. All rights reserved. Evaluation of Corrosion Inhibition of Mild Steel in 1 M Hydrochloric Acid Solution by Mollugo cerviana Mon, 21 Jul 2014 08:33:18 +0000 The inhibiting effect of methanolic extract of Mollugo cerviana plant on the corrosion of mild steel in 1 M HCl solution has been investigated by different techniques like potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss methods for five different concentrations of plant extract ranging from 25 to 1000 mg/L. The results indicated that the corrosion inhibition efficiency increased on increasing plant extract concentration till 500 mg/L and decreased on further increasing concentration. The extract was a mixed type inhibitor with the optimum inhibition concentration of 500 mg/L in potentiodynamic polarization. The adsorption of the plant extract on the mild steel surface was found to obey Langmuir adsorption isotherm. Surface analysis was also carried out to find out the surface morphology of the mild steel in the presence and in the absence of the inhibitor to find out its efficiency. The obtained results showed that the Mollugo cerviana extract acts as a good inhibitor for the corrosion of mild steel in 1 M HCl solution. P. Arockiasamy, X. Queen Rosary Sheela, G. Thenmozhi, M. Franco, J. Wilson Sahayaraj, and R. Jaya Santhi Copyright © 2014 P. Arockiasamy et al. All rights reserved. Corrosion Behavior of A356-10 Vol.% SiC Composites Cast by Gravity and Squeeze Casting in H2SO4 Solutions Tue, 08 Jul 2014 00:00:00 +0000 Corrosion behavior of A356-10 vol.% SiC composites cast by gravity and squeeze casting is evaluated. For this purpose, prepared samples were immersed in H2SO4 solution for 2 hrs. at open circuit potential. Tafel polarization and electrochemical impedance spectroscopy (EIS) were carried out to study the corrosion resistance of composites. The results showed that corrosion resistance of composites cast by squeeze casting is higher than that of the gravity cast composites. The micrographs of scanning electron microscope (SEM) clearly showed the squeeze casting composites exhibit a good dispersion/matrix interface when compared with composites produced by gravity casting. A. Fattah-alhosseini, M. Ranjbaran, and S. Vajdi Vahid Copyright © 2014 A. Fattah-alhosseini et al. All rights reserved. Effect of Cold-Rolled Thickness Reduction Degree on Characteristics of Hydrogen Diffusion in Silicon Steel Tue, 17 Jun 2014 08:17:38 +0000 The characteristic of hydrogen uptake and diffusion in the cold-rolled silicon steel was investigated by electrochemical hydrogen permeation technique performed under different cathodic charging current density and cold-rolled thickness reduction degree. The results indicated that anodic permeation current density increased with increasing cathodic charging current for the specimens. Moreover, the anodic steady state permeation current density and the solubility increased with an increase in the cold-rolled thickness reduction degrees. The breakthrough time of hydrogen in the specimens was shortened with increasing thickness reduction degrees, and the value of the hydrogen diffusivity decreased gradually with increasing thickness reduction degrees. Yongfeng Li, Lian Cai, Guanjun Liu, and Lijie Ma Copyright © 2014 Yongfeng Li et al. All rights reserved. Characterization of Corrosion Products on Carbon Steel Exposed to Natural Weathering and to Accelerated Corrosion Tests Sun, 15 Jun 2014 05:09:10 +0000 The aim of this work was to compare the corrosion products formed on carbon steel plates submitted to atmospheric corrosion in urban and industrial atmospheres with those formed after accelerated corrosion tests. The corrosion products were characterized by X-ray diffraction, Mössbauer spectroscopy, and Raman spectroscopy. The specimens were exposed to natural weathering in both atmospheres for nine months. The morphologies of the corrosion products were evaluated using scanning electron microscopy. The main product found was lepidocrocite. Goethite and magnetite were also found on the corroded specimens but in lower concentrations. The results showed that the accelerated test based on the ASTM B117 procedure presented poor correlation with the atmospheric corrosion tests whereas an alternated fog/dry cycle combined with UV radiation exposure provided better correlation. Renato Altobelli Antunes, Rodrigo Uchida Ichikawa, Luis Gallego Martinez, and Isolda Costa Copyright © 2014 Renato Altobelli Antunes et al. All rights reserved. Corrosion Problems in Incinerators and Biomass-Fuel-Fired Boilers Mon, 12 May 2014 06:15:28 +0000 Incinerators are widely used to burn the municipal waste, biowaste, wood, straw, and biomedical waste. Combustion of these types of waste results in generation of chlorides of sodium and potassium which may attack the metallic part of the incinerator. In biofuel-fired boilers, similar type of highly corrosive environment is present. Attempt has been made to review the corrosion problems and their solutions as per the available literature. Deepa Mudgal, Surendra Singh, and Satya Prakash Copyright © 2014 Deepa Mudgal et al. All rights reserved. Hot Corrosion Behaviour of Detonation Gun Sprayed Stellite-6 and Stellite-21 Coating on Boiler Steel SAE 431 at 900°C Tue, 06 May 2014 07:35:13 +0000 Hot corrosion is the serious problem in gas turbines, superheaters, and economizers of coal-fired boilers. It occurs due to the usage of wide range of fuels such as coal, oil, and so on at the elevated temperatures. Protective coatings on boiler steels are used under such environments. In the present investigation, Stellite-6 and Stellite-21 coatings have been deposited on boiler steel SAE 431 by detonation gun method. The hot corrosion performance of Stellite-6 and Stellite-21 coated as well as uncoated SAE 431 steel has been evaluated in aggressive environment of Na2SO4-82%Fe2(SO4)3 under cyclic conditions at an elevated temperature of 900°C for total duration of 50 cycles. Thermogravimetric technique was used to approximate the kinetics of hot corrosion. Stellite-6 coating imparted better hot corrosion resistance than Stellite-21 coating in the given environment. Scanning electron microscopy was used to characterize the surface of hot corrosion products. N. K. Mishra, A. K. Rai, S. B. Mishra, and R. Kumar Copyright © 2014 N. K. Mishra et al. All rights reserved. Assessment of Automotive Coatings Used on Different Metallic Substrates Tue, 29 Apr 2014 08:54:14 +0000 Four epoxy primers commonly used in the automotive industry were applied by gravity pneumatic spray gun over metallic substrates, specifically, steel, electrogalvanized steel, hot-dip galvanized steel, and aluminum. A two-component polyurethane resin was used as topcoat. To evaluate the performance of the different coating systems, the treated panels were submitted to mechanical testing using Persoz hardness, impact resistance, cupping, lattice method, and bending. Tribological properties of different coating systems were conducted using pin on disc machine. Immersion tests were carried out in 5% NaCl and immersion tests in 3% NaOH solutions. Results showed which of the coating systems is more suitable for each substrate in terms of mechanical, tribological, and anticorrosive performance. W. Bensalah, N. Loukil, M. De-Petris Wery, and H. F. Ayedi Copyright © 2014 W. Bensalah et al. All rights reserved. Corrosion of Steel in High-Strength Self-Compacting Concrete Exposed to Saline Environment Wed, 23 Apr 2014 14:29:26 +0000 A research work was carried out to investigate the effectiveness of high-strength self-compacting concrete (SF-R) in controlling corrosion of embedded steel. Reinforced concrete cylinders and plain cubes were subjected to 5% NaCl solution. Slump flow, J-ring, V-funnel, compressive strength, electrical resistance, and electrochemical tests were conducted. Corrosion resisting characteristics of steel were examined by monitoring corrosion potential, polarization resistance, corrosion currents, and Tafel plots. The relationship between corrosion current density and corrosion potential was established. Results were compared with characteristics of a grade 40 MPa reference concrete (R) and grade 70 MPa conventional self-compacting concrete (SP). Results indicated that at 270 days of exposure, the corrosion currents for steel in SF-R were 63- and 16-fold lower compared to those of steel in R and SP concretes, respectively. This concrete showed a considerable increase in electrical resistance and compressive strength of 96 MPa at 28 days of exposure. Relying on corrosion risk classification based on corrosion current densities and corrosion potentials, the steel in SF-R concrete is definitely in the passive condition. The splendid durability performance of steel in SF-R concrete linked to adorable self-compacting features could furnish numerous opportunities for future structural applications in severe environmental conditions. Hana A. Yousif, Farqad F. Al-Hadeethi, Bashar Al-Nabilsy, and Amani N. Abdelhadi Copyright © 2014 Hana A. Yousif et al. All rights reserved. Laboratory Assessment of Select Methods of Corrosion Control and Repair in Reinforced Concrete Bridges Thu, 10 Apr 2014 12:37:28 +0000 Fourteen reinforced concrete laboratory test specimens were used to evaluate a number of corrosion control (CoC) procedures to prolong the life of patch repairs in corrosion-damaged reinforced concrete. These specimens included layered mixed-in chlorides to represent chloride contamination due to deicing salts. All specimens were exposed to accelerated corrosion testing for three months, subjected to patch repairs with various treatments, and further subjected to additional three months of exposure to accelerated corrosion. The use of thermal sprayed zinc, galvanic embedded anodes, epoxy/polyurethane coating, acrylic coating, and an epoxy patch repair material was evaluated individually or in combination. The specimens were assessed with respect to corrosion currents (estimated mass loss), chloride ingress, surface rust staining, and corrosion of the reinforcing steel observed after dissection. Results indicated that when used in patch repair applications, the embedded galvanic anode with top surface coating, galvanic thermal sprayed zinc, and galvanic thermal sprayed zinc with surface coating were more effective in controlling corrosion than the other treatments tested. Matthew D. Pritzl, Habib Tabatabai, and Al Ghorbanpoor Copyright © 2014 Matthew D. Pritzl et al. All rights reserved. Simulation of the Relaxation Potential Profile of an ac-dc-ac Test Thu, 03 Apr 2014 06:42:45 +0000 The relaxation period of the accelerated ac-dc-ac test for coatings is associated with the transient electrochemistry that occurs when the immersed coated system is allowed to return to a stable open-circuit condition after being subjected to a cathodic potential. A mathematical model of the transient electrochemistry that occurs during this relaxation period is presented for coated aluminum. Expressions for the corrosion potential and corrosion current as functions of the local pH at the metal-coating interface were developed using reported experimental results. These expressions enabled the simulation of the transient electrochemistry under the constraint of balanced anodic and cathodic current densities. Regression of the transient relaxation potential profiles to exponential decay functions provided time-constant characterization of the profiles. Simulated results are presented that demonstrate the influences of the coating's porosity and thickness, the applied dc potential and the metal-coating interface condition on the time-constants associated with the relaxation profile. Interpretation of experimentally reported relaxation potential profiles supported the analysis of the simulated results. Kerry N. Allahar, Michael F. Hurley, Erik D. Sapper, and Darryl P. Butt Copyright © 2014 Kerry N. Allahar et al. All rights reserved. Parameter Studies on High-Velocity Oxy-Fuel Spraying of CoNiCrAlY Coatings Used in the Aeronautical Industry Thu, 06 Mar 2014 10:57:48 +0000 The thermal spraying process is a surface treatment which does not adversely affect the base metal on which it is performed. The coatings obtained by HVOF thermal spray are employed in aeronautics, aerospace, and power generation industries. Alloys and coatings designed to resist oxidizing environments at high temperatures should be able to develop a surface oxide layer, which is thermodynamically stable, slowly growing, and adherent. MCrAlY type (M = Co, Ni or combination of both) coatings are used in wear and corrosion applications but also provide protection against high temperature oxidation and corrosion attack in molten salts. In this investigation, CoNiCrAlY coatings were produced employing a HVOF DJH 2700 gun. The work presented here focuses on the influences of process parameters of a gas-drive HVOF system on the microstructure, adherence, wear, and oxygen content of CoNiCrAlY. The results showed that spray distance significantly affects the properties of CoNiCrAlY coatings. J. A. Cabral-Miramontes, C. Gaona-Tiburcio, F. Almeraya-Calderón, F. H. Estupiñan-Lopez, G. K. Pedraza-Basulto, and C. A. Poblano-Salas Copyright © 2014 J. A. Cabral-Miramontes et al. All rights reserved. Effect of C/Si Ratio on the Electrochemical Behavior of a-SiCx:H Coatings on SS301 Substrate Deposited by PECVD Wed, 05 Mar 2014 15:27:44 +0000 Amorphous hydrogenated silicon carbide (a-SiCx:H) coatings were deposited on stainless steel 301 (SS301) using plasma enhanced chemical vapor deposition with the methane gas flow ranging from 30 to 90 sccm. XRD spectra confirmed the amorphous structure of these coatings. The as-deposited coatings all exhibited homogenous dense feature, and no porosities were observed in SEM and AFM analysis. The a-SiCx:H coatings remarkably increased the corrosion resistance of the SS301 substrate. With the increase of the C concentration, the a-SiCx:H coatings exhibited significantly enhanced electrochemical behavior. The a-SiCx:H coating with the highest carbon concentration acted as an excellent barrier to charge transfer, with a corrosion current of  A/cm2 and a breakdown voltage of 1.36 V, compared to  A/cm2 and 0.34 V for the SS301 substrate. D. Li, S. Guruvenket, J. A. Szpunar, and J. E. Klemberg-Sapieha Copyright © 2014 D. Li et al. All rights reserved. Protection of Steel Corrosion in Concrete Members by the Combination of Galvanic Anode and Nitrite Penetration Wed, 12 Feb 2014 09:39:32 +0000 Chloride induced-corrosion of steel bars in concrete can make cracks and exfoliation in near-surface regions in reinforced concrete structures. In this paper, we described the basic concept and practice of steel bars corrosion protection method by the combination of galvanic anode (zinc wire) and the penetration of nitrite ions from mortar layers containing a large amount of lithium nitrite. Minobu Aoyama, Shinichi Miyazato, and Mitsunori Kawamura Copyright © 2014 Minobu Aoyama et al. All rights reserved. Boric Acid as an Accelerator of Cerium Surface Treatment on Aluminum Thu, 16 Jan 2014 07:26:37 +0000 Aluminum pieces are often used in various industrial processes like automotive and aerospace manufacturing, as well as in ornamental applications, so it is necessary to develop processes to protect these materials, processes that can be industrialized to protect the aluminum as well or better than chromate treatments. The purpose of this research is to evaluate boric acid as an accelerator by optimizing its concentration in cerium conversion coatings (CeCC) with 10-minute immersion time with a concentration of 0.1 g L−1 over aluminum to protect it. The evaluation will be carried out by measuring anticorrosion properties with electrochemical techniques (polarization resistance, , polarization curves, PC, and electrochemical impedance spectroscopy, EIS) in NaCl 3.5% wt. aqueous solution and surface characterization with scanning electron microscopy (SEM). K. Cruz-Hernández, S. López-Leon, and F. J. Rodríguez-Gómez Copyright © 2014 K. Cruz-Hernández et al. All rights reserved. Approaches for Modelling the Residual Service Life of Marine Concrete Structures Sun, 12 Jan 2014 16:57:10 +0000 This paper deals with the service life design of existing reinforced concrete structures in a marine environment. The general procedure of condition assessment for estimating the residual service life of structures before a repair measure is illustrated. For assessment of the residual service life of structures which have undergone a repair measure a simplified mathematical model of chloride diffusion in a 2-layer system is presented. Preliminary probabilistic calculations demonstrate the effect of various conditions on the residual service life. First studies of the chloride diffusion in a 2-layer system have been conducted using the finite element method. Results of a long-term exposure test are presented to illustrate the performance of two different repair materials. The distribution of residual chlorides after application of a repair material is being studied in laboratory investigations. The residual chlorides migrate from the concrete layer into the new layer immediately after the repair material has been applied to the concrete member. The content and gradient of residual chlorides, along with the thickness and the chloride ingress resistance of both the remaining and the new layer of cover, will determine the residual service life of the repaired structures. Amir Rahimi, Christoph Gehlen, Thorsten Reschke, and Andreas Westendarp Copyright © 2014 Amir Rahimi et al. All rights reserved. Theoretical Study of Chloro-N-(4-methoxybenzylidene)aniline Derivatives as Corrosion Inhibitors for Zinc in Hydrochloric Acid Thu, 26 Dec 2013 10:54:56 +0000 The density functional theory (DFT) was used to investigate the corrosion inhibition of three inhibitors on zinc. Quantum chemical parameters such as the energy of highest occupied molecular orbital (), the energy of lowest unoccupied molecular orbital (), energy gap , hardness , softness , electrophilicity index , the fraction of electrons transferred from inhibitor molecule to the metal surface, energy change when both processes occur, namely, charge transfer to the molecule and backdonation from the molecule (), natural charge , and Fukui functions have been calculated by using B3LYP/6-31+G(d) basis set. The relation between the inhibition efficiency and quantum chemical parameters has been discussed in order to elucidate the inhibition mechanism of the chloro-N-(4-methoxybenzylidene)aniline derivatives. S. Kumar, D. G. Ladha, P. C. Jha, and N. K. Shah Copyright © 2013 S. Kumar et al. All rights reserved. Garcinia indica as an Environmentally Safe Corrosion Inhibitor for Aluminium in 0.5 M Phosphoric Acid Thu, 19 Dec 2013 14:49:04 +0000 The Inhibitive and adsorption properties of aqueous extract of seeds of Garcinia indica extract (GIE) have been studied for corrosion control of aluminium in 0.5 M phosphoric acid solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques at to . The effects of inhibitor concentration on the inhibition action were investigated. Polarization measurements showed that the GIE acted as mixed inhibitor and the inhibitor molecules followed chemical adsorption on the surface of aluminium. The adsorption of GIE on metal surface obeyed Langmuir adsorption isotherm. The surface morphology of aluminium, in the absence and in the presence of GIE in 0.5 M phosphoric acid solution, was studied using scanning electron microscopy (SEM). Results obtained from both of the electrochemical techniques were in good agreement with each other. Deepa Prabhu and Padmalatha Rao Copyright © 2013 Deepa Prabhu and Padmalatha Rao. All rights reserved.