International Journal of Corrosion The latest articles from Hindawi Publishing Corporation © 2016 , Hindawi Publishing Corporation . All rights reserved. Investigation of Stress Concentration and Casing Strength Degradation Caused by Corrosion Pits Wed, 09 Nov 2016 14:11:49 +0000 Downhole casing and tubing are subjected to corrosion in many cases because of the exposure to corrosive environment. A more serious problem is that pitting corrosion occurs in the casing inner surface. Meanwhile, downhole strings are subjected to various forms of mechanical loads, for example, internal pressure load, external collapse load, or both. These loads acting on the corrosion pits will cause stress concentration and degrade the casing strength. Thus, it is essential to evaluate the stress concentration degree reasonably. The SCF (stress concentration factor) is usually used to characterize the degree of stress concentration induced by corrosion pits. This paper presented a comparison on the SCFs regarding the analytical method for a single pit and experimental method for double pits. The results show that the SCF of a single pit depends mainly on the depth of the corrosion pit; however, the SCF of the double pits strongly depends on the pits distance. A correction factor of 1.3 was recommended in the double pits SCF prediction model. Wei Yan, Yun Xu, Yi Zhou, and Kongyang Wang Copyright © 2016 Wei Yan et al. All rights reserved. Protection against Corrosion of Aluminum Alloy in Marine Environment by Lawsonia inermis Wed, 09 Nov 2016 09:20:55 +0000 The corrosion performance of aluminum alloy 5083 (AA5083) was investigated in the splash zone area simulated in salt spray cabinet at ambient temperature. Three paint formulations were prepared in accordance with different percentages of henna extract. FTIR method was used to determine the constituent of henna while weight loss and electrochemical method were applied to investigate the inhibition behaviour. The findings show that corrosion rate of aluminum alloy decreased with the increases of henna extract in the coating formulation. The rise of charge transfer resistance () value has contributed to the greater protection of the coated aluminum. The decrease in double layer capacitance value () is another indicator that a better protective barrier has been formed in the presence of henna in the coating matrix. H. M. Hajar, F. Zulkifli, M. G. Mohd Sabri, and W. B. Wan Nik Copyright © 2016 H. M. Hajar et al. All rights reserved. Experimental Investigation on Corrosion Effect on Mechanical Properties of Buried Metal Pipes Thu, 08 Sep 2016 09:17:13 +0000 Corrosion has been found to be the most predominant cause for failures of buried metal pipes. A review of published literature on pipe corrosion reveals that little research has been undertaken on the effect of corrosion on mechanical properties of pipe materials and almost no research has been conducted on corrosion effect on fracture toughness. The intention of this paper is to present a comprehensive test program designed to investigate the effect of corrosion on mechanical properties of metals in soil. Two types of metals, namely, cast iron and steel, are tested under corrosion in three different environments. A relationship between corrosion and deterioration of mechanical property of metals is developed. It is found in the paper that the more acidic the environment is, the more corrosion the metal undergoes and that the corrosion reduces both the tensile strength and fracture toughness of the metal. The results presented in the paper can contribute to the body of knowledge of corrosion behavior and its effect on mechanical properties of metals in soil environment, which in turn enable more accurate prediction of failures of buried metal pipes. Yingbo Hou, Deqing Lei, Shujin Li, Wei Yang, and Chun-Qing Li Copyright © 2016 Yingbo Hou et al. All rights reserved. Inhibition of Corrosion of Carbon Steel in 3.5% NaCl Solution by Myrmecodia Pendans Extract Wed, 31 Aug 2016 16:15:14 +0000 Inhibitor is a substance that is added to the corrosive media to inhibit corrosion rate. Organic inhibitors are preferred to inorganic ones since they are environmentally friendly. One of the organic compounds which is rarely reported as a corrosion inhibitor is Myrmecodia Pendans. The organic compounds can be adsorbed on the metal surface and block the active surface to reduce the rate of corrosion. In this study, the used pipe was carbon steel API 5L Grade B with 3.5% NaCl solution as the corrosion medium. The objective of this research was to analyze the inhibition mechanism Myrmecodia Pendans towards carbon steel in a corrosion medium. Concentration variations of extract Myrmecodia Pendans were 0–500 ppm. Fourier Transform Infrared (FTIR) was used for chemical characterization of Myrmecodia Pendans. Polarization and Electrochemical Impedance Spectroscopy (EIS) were used to measure the corrosion rate and behaviour. From the electrochemical measurements, it was found that the addition of 400 mg/L inhibitor gave the highest inhibition efficiency. Myrmecodia Pendans acted as a corrosion inhibitor by forming a thin layer on the metal surface. Atria Pradityana, Sulistijono, Abdullah Shahab, Lukman Noerochim, and Diah Susanti Copyright © 2016 Atria Pradityana et al. All rights reserved. Electrochemical and Microstructural Analysis of FeS Films from Acidic Chemical Bath at Varying Temperatures, pH, and Immersion Time Tue, 23 Aug 2016 13:55:29 +0000 The corrosion resistance and corrosion products of 4130 alloy steel have been investigated by depositing thin films of iron sulfide synthesized from an acidic chemical bath. Tests were conducted at varying temperatures (25°C–75°C), pH levels (2–4), and immersion time (24–72 hours). The corrosion behavior was monitored by linear polarization resistance (LPR) method. X-ray Diffraction (XRD), Energy Dispersive X-ray (EDX) spectroscopy, and Scanning Electron Microscopy (SEM) have been applied to characterize the corrosion products. The results show that, along with the formation of an iron sulfide protective film on the alloy surface, increasing temperature, increasing immersion time, and decreasing pH all directly increase the corrosion rate of steel in the tested experimental conditions. It was also concluded that increasing temperature causes an initial increase of the corrosion rate followed by a large decrease due to transformation of the iron sulfide crystalline structure. Ladan Khaksar, Gary Whelan, and John Shirokoff Copyright © 2016 Ladan Khaksar et al. All rights reserved. Effect of Additional Sulfide and Thiosulfate on Corrosion of Q235 Carbon Steel in Alkaline Solutions Mon, 15 Aug 2016 09:16:28 +0000 This paper investigated the effect of additional sulfide and thiosulfate on Q235 carbon steel corrosion in alkaline solutions. Weight loss method, scanning electron microscopy (SEM) equipped with EDS, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements were used in this study to show the corrosion behavior and electrochemistry of Q235 carbon steel. Results indicate that the synergistic corrosion rate of Q235 carbon steel in alkaline solution containing sulfide and thiosulfate is larger than that of sulfide and thiosulfate alone, which could be due to redox reaction of sulfide and thiosulfate. The surface cracks and pitting characteristics of the specimens after corrosion were carefully examined and the corrosion products film is flake grains and defective. The main corrosion products of specimen induced by S2− and S2 are FeS, FeS2, Fe3O4, and FeOOH. The present study shows that the corrosion mechanism of S2− and S2 is different for the corrosion of Q235 carbon steel. Bian Li Quan, Jun Qi Li, and Chao Yi Chen Copyright © 2016 Bian Li Quan et al. All rights reserved. Long Term Corrosion Experiment of Steel Rebar in Fly Ash-Based Geopolymer Concrete in NaCl Solution Mon, 15 Aug 2016 06:05:53 +0000 This research focuses on an experimental investigation to identify the effects of fly ash on the electrochemical process of concrete during the curing time. A rebar was analysed using potentiostat to measure the rest potential, polarization diagram, and corrosion rate. Water-to-cement ratio and amount of fly ash were varied. After being cured for 24 hours at a temperature of 65°C, the samples were immersed in 3.5% of NaCl solution for 365 days for electrochemical measurement. Measurements of the half-cell potential and corrosion current density indicated that the fly ash has significant effects on corrosion behaviour of concrete. Although fly ash tends to create passivity on anodic current, it increases corrosion rate. The corrosion potential of this concrete mixture decreases compared to concrete without fly ash. From the result, it can be summarized that concrete mixture with 70% of OPC (Ordinary Portland Cement) and 30% fly ash has shown the best corrosion resistance. Y. P. Asmara, J. P. Siregar, C. Tezara, Wan Nurlisa, and J. Jamiluddin Copyright © 2016 Y. P. Asmara et al. All rights reserved. A Probabilistic Physics of Failure Approach for Structure Corrosion Reliability Analysis Sun, 14 Aug 2016 11:15:14 +0000 Corrosion is recognized as one of the most important degradation mechanisms that affect the long-term reliability and integrity of metallic structures. Studying the structural reliability with pitting corrosion damage is useful for risk control and safety operation for the corroded structure. This paper proposed a structure corrosion reliability analysis approach based on the physics-based failure model of pitting corrosion, where the states of pitting growth, pit-to-crack, and cracking propagation are included in failure model. Then different probabilistic analysis methods such as Monte-Carlo Simulation (MCS), First-Order Reliability Method (FORM), Second-Order Reliability Method (SORM), and response surface method are employed to calculate the reliability. At last, an example is presented to demonstrate the capability of the proposed structural reliability model and calculating methods for structural corrosion failure analysis. Chaoyang Xie and Hong-Zhong Huang Copyright © 2016 Chaoyang Xie and Hong-Zhong Huang. All rights reserved. Seismic Behavior of Corroded RC Bridges: Review and Research Gaps Thu, 19 May 2016 16:25:49 +0000 Chloride-induced corrosion and its effect on structural and seismic performance of reinforced concrete (RC) structures have been the topic of several research projects in past decades. This literature review summarizes the state of the art by presenting a brief description of chloride-induced corrosion, its main characteristics and influencing factors, a summary of experimental published data, and existing corrosion-induced deterioration models together with numerical and experimental methods used to evaluate corroded RC bridge pier. This literature review highlights the need for reliable deterioration models for RC structures and appropriate analysis methods are needed for design of new structures or assessment of existing civil engineering structures especially in seismic areas. Kaveh Andisheh, Allan Scott, and Alessandro Palermo Copyright © 2016 Kaveh Andisheh et al. All rights reserved. Simulation of the Ill-Posed Problem of Reinforced Concrete Corrosion Detection Using Boundary Element Method Wed, 06 Apr 2016 09:29:17 +0000 Many studies have suggested that the corrosion detection of reinforced concrete (RC) based on electrical potential on concrete surface was an ill-posed problem, and thus it may present an inaccurate interpretation of corrosion. However, it is difficult to prove the ill-posed problem of the RC corrosion detection by experiment. One promising technique is using a numerical method. The objective of this study is to simulate the ill-posed problem of RC corrosion detection based on electrical potential on a concrete surface using the Boundary Element Method (BEM). BEM simulates electrical potential within a concrete domain. In order to simulate the electrical potential, the domain is assumed to be governed by Laplace’s equation. The boundary conditions for the corrosion area and the noncorrosion area of rebar were selected from its polarization curve. A rectangular reinforced concrete model with a single rebar was chosen to be simulated using BEM. The numerical simulation results using BEM showed that the same electrical potential distribution on the concrete surface could be generated from different combinations of parameters. Corresponding to such a phenomenon, this problem can be categorized as an ill-posed problem since it has many solutions. Therefore, BEM successfully simulates the ill-posed problem of reinforced concrete corrosion detection. Syarizal Fonna, Israr M. Ibrahim, M. Ridha, Syifaul Huzni, and A. K. Ariffin Copyright © 2016 Syarizal Fonna et al. All rights reserved. Adaptive Corrosion Protection System Using Continuous Corrosion Measurement, Parameter Extraction, and Corrective Loop Thu, 17 Mar 2016 06:33:52 +0000 A simple current-sourced adaptive corrosion protection system (ACPS) along with a technology to extract the protection current from the Tafel plot is presented. For reliable protection of the target metal, first, the Tafel plot of the target metal is obtained. Subsequently, a novel technique proposed in this paper is used to extract the protection current from the Tafel plot. This extracted protection current is fed to the target metal to protect the metal in the existing corrosive environment. This three-part system is adaptively used to update the required protection current to effectively protect the target metal continuously. All these functionalities are integrated in a stand-alone ACPS that effectively diagnoses the corrosion status and updates the protection parameters without any manual interaction or physical modification of the set-up to offer modularity, reliability, and cost saving. To validate the technique, a laboratory scale system is realized and tested using various metal samples and various corrosive mediums. Using the experimental system, A36 metal coupons are effectively protected with protection (inhibition) efficiency of 40–100 in different corrosive mediums that can extend the life expectancy of the target metal from ~2 times to more than 100 times for the tested corrosive mediums. Jasbir N. Patel, Andre Chang, Haleh Shahbazbegian, and Bozena Kaminska Copyright © 2016 Jasbir N. Patel et al. All rights reserved. Study of New Thiazole Based Pyridine Derivatives as Potential Corrosion Inhibitors for Mild Steel: Theoretical and Experimental Approach Thu, 03 Mar 2016 13:07:16 +0000 Three new thiazole based pyridine derivatives 5-(4-methoxy-phenyl)-thiazole-2-carboxylic acid pyridin-2-ylmethylene-hydrazide (2-MTPH), 5-(4-methoxy-phenyl)-thiazole-2-carboxylic acid pyridin-3-ylmethylene-hydrazide (3-MTPH), and 5-(4-methoxy-phenyl)-thiazole-2-carboxylic acid pyridin-4-ylmethylene-hydrazide (4-MTPH) were synthesized and characterized. Corrosion inhibition performance of the prepared compounds on mild steel in 0.5 M HCl was studied using gravimetric, potentiodynamic polarisation, and electrochemical impedance techniques. Inhibition efficiency has direct relation with concentration and inverse relation with temperature. Thermodynamic parameters for dissolution and adsorption process were evaluated. Polarisation study reveals that compounds act as both anodic and cathodic inhibitors with emphasis on the former. Impedance study shows that decrease in charge transfer resistance is responsible for effective protection of steel surface by inhibitors. The film formed on the mild steel was investigated using FTIR, SEM, and EDX spectroscopy. Quantum chemical parameters like , , , hardness, softness, and ionisation potential were calculated. Higher value of and lower value of indicate the better inhibition efficiency of the compounds. Lower ionisation potential of inhibitors indicates higher reactivity and lower chemical stability. T. K. Chaitra, K. N. Mohana, and H. C. Tandon Copyright © 2016 T. K. Chaitra et al. All rights reserved. A Study of N,N-Diethylammonium O,O′-Di(p-methoxyphenyl)dithiophosphate as New Corrosion Inhibitor for Carbon Steel in Hydrochloric Acid Solution Thu, 18 Feb 2016 07:03:07 +0000 N,N-Diethylammonium O,O′-di(p-methoxyphenyl)dithiophosphate (EAPP) as a new corrosion inhibitor was synthesized in the present work. The corrosion inhibition of EAPP in hydrochloric acid for carbon steel was evaluated by potentiodynamic polarization measurements, electrochemical impedance spectroscopy, weight loss measurements, and scanning electron microscopy. The results indicate that the EAPP is mixed type inhibitor, and the adsorption of EAPP on carbon steel surface obeys Langmuir isotherm. In addition, the inhibition efficiency increases with increasing the concentration of inhibitor and decreases with increasing the hydrochloric acid concentration, temperature, and storage time. Chuan Lai, Bin Xie, Changlu Liu, Wan Gou, Lvshan Zhou, Xiulan Su, and Like Zou Copyright © 2016 Chuan Lai et al. All rights reserved. Corrosion Behavior of Carbon Steels in CCTS Environment Thu, 04 Feb 2016 07:38:42 +0000 The paper reports the results of an experimental work on the effect of steel microstructures on morphology and protectiveness of the corrosion scale formed in water saturated by supercritical CO2. Two HSLA steels were tested. The microstructures were modified by means of different heat treatments. Weight loss was measured after exposure at CO2 partial pressure of 80 bar and 60°C temperature. The morphology of the scale was analyzed by means of scanning electron microscope (SEM) energy-dispersive X-ray spectroscopy (EDX). Cathodic potentiodynamic tests were carried out on precorroded specimens for evaluating the effect of preformed scales on cathodic polarization curves in CO2 saturated sulphuric acid solution at pH 3, which is the value estimated for water saturated by supercritical CO2. The results are discussed in order to evaluate the effect of iron carbide network on scale growth and corrosion rate. Weight loss tests evidenced average corrosion rate values in the range 1–2.5 mm/y after 150-hour exposure. The presence of thick siderite scale significantly reduces the corrosion rate of carbon steel. A slight decrease of the corrosion rate was observed as the scale thickness increases and moving from martensite to microstructures containing carbides. M. Cabrini, S. Lorenzi, and T. Pastore Copyright © 2016 M. Cabrini et al. All rights reserved. Experimental Study on the Influence of AC Stray Current on the Cathodic Protection of Buried Pipe Tue, 19 Jan 2016 13:57:38 +0000 The size of the damaged area of the coating and its position on the pipeline impacted the cathodic protection potential, and there was a damaged area of the greatest impact value. When damaged area was 300 mm2, the IR drop was the largest, and this situation could easily lead to inadequate protection; when the parallel spacing between pipeline and interference source was unchanged, the measured value curves of cathodic protection potential presented “U” shaped trend with the increasing stray current interference intensity. Under certain parallel spacing between pipeline and interference source, high alternating stray current intensity would cause serious negative offsets, so that the overprotection of the pipeline occurred, and make the coating crack; there was a parallel threshold length. When less than the threshold, the pipe-ground potential increases rapidly with the parallel length increasing. In order to judge whether a pipeline was interference by AC stray current and the risk of stray current corrosion, we should make a comprehensive analysis of the cathodic protection energizing potential, the switch-off potential, AC pipe-soil potential, IR drops, and so on. Qingmiao Ding and Yueming Fan Copyright © 2016 Qingmiao Ding and Yueming Fan. All rights reserved. Pomegranate (Punica granatum) Peel Extract as a Green Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution Tue, 24 Nov 2015 08:17:10 +0000 The inhibition effect of pomegranate peel extract (PPE) on the corrosion of mild steel in hydrochloric acid (HCl) solution was investigated. The polarization, mass loss, and electrochemical impendence techniques were used to evaluate the corrosion inhibition performance of the pomegranate peel extract. The results revealed that PPE acts as a corrosion inhibitor in HCl solution. The inhibition efficiency increased with the increase of extract concentration. The inhibition action was attributed to the adsorption of the chemical compounds present in the extract solution, on mild steel surface. Habib Ashassi-Sorkhabi, Shoja Mirzaee, Taghi Rostamikia, and Robabeh Bagheri Copyright © 2015 Habib Ashassi-Sorkhabi et al. All rights reserved. Effect of Electrical Injection of Corrosion Inhibitor on the Corrosion of Steel Rebar in Chloride-Contaminated Repair Mortar Mon, 16 Nov 2015 14:00:12 +0000 The electrical rehabilitation treatments of repair mortar were performed with tetrabutylammonium bromide salt (TBAB) at an electrical current density of 5 A/m2, using two electrolytes (0.1 M NaOH and 0.1 M Na3BO3 solutions), and for two time periods (1 and 4 weeks), respectively. The average organic cation-based inhibitor’s concentration in cement mortars before and after this treatment was quantified using the UV-Vis spectroscopy. The experimental results reveal that the EICI treatment with 0.1 M Na3BO3 was more effective in injecting the inhibitor and in improving the chloride penetration resistance and compressive strength of the mortar, relative to using 0.1 M NaOH as electrolyte. In this case, after the 4-week EICI treatment, [TBA+] contents were 2.3 % and 2.4% by mass of cement mortar for uncontaminated and salt-contaminated mortars, respectively. After the 4-week EICI treatment, the apparent diffusion coefficients of chloride anion in cement mortar were decreased by 40% from 1.52 × 10−10 m2/s. The EICI treatment was able to halt the chloride-induced corrosion of the steel rebar by promoting its passivation. The 2-week EICI treatment using sodium hydroxide and sodium borate solutions decreased the corrosion current density of the rebar by 77.8% and 78.5%, respectively, approximately two months after the treatment. The Huyen Nguyen, Tuan Anh Nguyen, Thien Vuong Nguyen, Van Khu Le, Thi Mai Thanh Dinh, Hoang Thai, and Xianming Shi Copyright © 2015 The Huyen Nguyen et al. All rights reserved. Effect of High Temperature Sodium Hydroxide Immersion on Fusion Bond Epoxy Coating Mon, 28 Sep 2015 13:45:36 +0000 Fusion Bond Epoxy (FBE) coating system was exposed to 5% sodium hydroxide at elevated temperature for 30 days. The result of exposure showed formation of adhere deposit layer, a discolored zone underneath and remaining un-affected bulk of the coating. The deterioration of the coating was characterized using analytical techniques like scanning electron microscopy (SEM), energy-dispersive X-ray (EDAX) spectroscopy, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), pull-off adhesion, and electrochemical impedance spectroscopy (EIS). Results obtained indicated chemical deterioration of the coating in the discolored zone and leaching of low molecular weight coating component forming deposit layer. Although the adhesion strength and barrier property were not affected, the polymer matrix in the affected zone undergoes severe changes in its surface microstructure, primary chemical structure, and glass transition temperature. This may inflict serious impairment of the coating functional properties and premature failure of the coating in long term exposure. Amal Al-Borno, Xianyi Chen, and Shailesh Kewaldas Dhoke Copyright © 2015 Amal Al-Borno et al. All rights reserved. Corrosion Behaviour of a Silane Protective Coating for NdFeB Magnets in Dentistry Mon, 21 Sep 2015 12:24:22 +0000 The corrosion behavior of coated and uncoated Ni/Cu/Ni rare earth magnets was assessed at increasing steps with a multilayering silanization procedure. Magnets’ durability was analyzed in Fusayama synthetic saliva solution in order to evaluate their application in dental field. Corrosion performance was evaluated by using polarization and electrochemical impedance spectroscopy in synthetic saliva solution up to 72 hours of continuous immersion. The results show that the addition of silane layers significantly improved anticorrosion properties. The coating and aging effects, in synthetic saliva solution, on magnetic field were evaluated by means of cyclic force-displacement curves. Luigi Calabrese, A. Caprì, F. Fabiano, L. Bonaccorsi, C. Borsellino, and Edoardo Proverbio Copyright © 2015 Luigi Calabrese et al. All rights reserved. Smart Mesoporous Silica Nanocapsules as Environmentally Friendly Anticorrosive Pigments Tue, 15 Sep 2015 09:40:10 +0000 Nowadays there is a special interest to study and develop new smart anticorrosive pigments in order to increase the protection life time of organic coatings and, simultaneously, to find alternatives to conventional toxic and carcinogenic hexavalent chromium compounds. In this respect, the great development of nanotechnologies in recent years has opened up a range of possibilities in the field of anticorrosive paints through the integration of encapsulated nanoscale containers loaded with active components into coatings. By means of a suitable design of the capsule, the release of the encapsulated corrosion inhibitor can be triggered by different external or internal factors (pH change, mechanical damage, etc.) thus preventing spontaneous leakage of the active component and achieving more efficient and economical use of the inhibitor, which is only released upon demand in the affected area. In the present work, the improved anticorrosive behaviour achieved by encapsulated mesoporous silica nanocontainers filled with an environmentally friendly corrosion inhibitor has been evaluated. It has been proven that a change in the pH allows the rupture of the capsules, the release of the inhibitor, and the successful protection of the carbon steel substrate. C. Zea, R. Barranco-García, B. Chico, I. Díaz, M. Morcillo, and D. de la Fuente Copyright © 2015 C. Zea et al. All rights reserved. Bee Wax Propolis Extract as Eco-Friendly Corrosion Inhibitors for 304SS in Sulfuric Acid Tue, 15 Sep 2015 08:11:16 +0000 The inhibition properties of bee wax propolis (BWP) extract on the 304SS in 0.5 M sulfuric acid were conducted using potentiodynamic polarization, EIS, and XRD. Quercetin (2-(3.4-dihydroxy phenyl)-3.5.7-trihydroxy-4H-chromen-4-one) was identified as the main compound in the BWP extract based on FTIR and HPLC analysis. The results showed that the inhibitor could retard the corrosion rate of 304SS in 0.5 M sulfuric acid which reached 97.29% and 91.42% at 2000 ppm based on potentiodynamic polarization and EIS measurement, respectively. The inhibition efficiency decreased with increasing temperature. The inhibition mechanism of BWP extract on the 304SS was physisorption and obeyed Temkin adsorption isotherm equation. The thin protective layer on the 304SS surface was confirmed by XRD. Femiana Gapsari, Rudy Soenoko, Agus Suprapto, and Wahyono Suprapto Copyright © 2015 Femiana Gapsari et al. All rights reserved. Study on Corrosion of Macroporous Silicon in Sodium Hydroxide Solution by Electrochemical Methods and Scanning Electron Microscopy Mon, 07 Sep 2015 11:01:36 +0000 The fabricated macroporous silicon with a porosity of 26.33% corrosion in NaOH solution was systemically investigated by open circuit potential measurements, linear polarization measurements, potentiodynamic polarization measurements, and scanning electron microscopy, respectively. Results show that the potential open circuit and linear polarization resistance decreases with the NaOH concentration increasing. The corrosion potential shifts significantly to more negative potentials and corrosion current density increases with NaOH concentration increasing. Adding ethanol to 1.0 M NaOH can lead to the linear polarization resistance decrease, corrosion potentials shift in the positive direction, and corrosion current density increase. In addition, the scanning electron microscopy images demonstrate that the macroporous silicon samples are seriously damaged by 1.0 M NaOH and 1.0 M NaOH/EtOH (30%). Chuan Lai, Zhen Xiang, Changlu Liu, Chaoju Zhu, Hui Wang, and Hui Zhu Copyright © 2015 Chuan Lai et al. All rights reserved. Surface Corrosion Resistance in Turning of Titanium Alloy Thu, 27 Aug 2015 12:42:53 +0000 This work addresses the issues associated with implant surface modification. We propose a method to form the oxide film on implant surfaces by dry turning to generate heat and injecting oxygen-rich gas at the turning-tool flank. The morphology, roughness, composition, and thickness of the oxide films in an oxygen-rich atmosphere were characterized using scanning electron microscopy, optical profiling, and Auger electron spectroscopy. Electrochemical methods were used to study the corrosion resistance of the modified surfaces. The corrosion resistance trends, analyzed relative to the oxide film thickness, indicate that the oxide film thickness is the major factor affecting the corrosion resistance of titanium alloys in a simulated body fluid (SBF). Turning in an oxygen-rich atmosphere can form a thick oxide film on the implant surface. The thickness of surface oxide films processed at an oxygen concentration of 80% was improved to 4.6 times that of films processed at an oxygen concentration of 21%; the free corrosion potential shifted positively by 0.357 V, which significantly improved the corrosion resistance of titanium alloys in the SBF. Therefore, the proposed method may (partially) replace the subsequent surface oxidation. This method is significant for biomedical development because it shortens the process flow, improves the efficiency, and lowers the cost. Rui Zhang, Xing Ai, Yi Wan, Zhanqiang Liu, Dong Zhang, and Sheng Feng Copyright © 2015 Rui Zhang et al. All rights reserved. Novel Synthesis of Vegetable Oil Derived Corrosion Inhibitors Wed, 15 Jul 2015 06:33:04 +0000 Two different naturally occurring vegetable oils, Cress seed oil, and Linseed oil were chemically modified via novel one pot synthesis to produce fatty acid derived amides. These were characterized by their ability to prevent corrosion of carbon steel in vigorously stirred, aerated seawater, one of the most corrosive naturally occurring environments. Corrosion inhibitor efficiencies of up to 99.6% or a corrosion rate reduction factor of 250 in this medium is reported. The one pot synthetic strategy means that the corrosion inhibitors can be made at very low cost. Paul Rostron and Sonia Kasshanna Copyright © 2015 Paul Rostron and Sonia Kasshanna. All rights reserved. The Pitting Susceptibility Investigation of Passive Films Formed on X70, X80, and X100 Pipeline Steels by Electrochemical Noise and Mott-Schottky Measurements Sun, 05 Jul 2015 14:01:51 +0000 The pitting susceptibility of passive films formed on X70, X80, and X100 pipeline steels was investigated by means of electrochemical noise (EN) and Mott-Schottky measurements. The EN results were analyzed according to the shot-noise theory and stochastic theory. Pit initiation process was analyzed quantitatively using the Weibull distribution function. Pit growth process was simulated by Gumbel distribution function. The experimental results of Mott-Schottky plots showed that the passive films formed on the three pipeline steels displayed an n-type semiconductor character, and the passive film for X100 pipeline steel has the lowest donor density () among the three passive films. The EN results demonstrated that X100 pipeline steel had the lowest pit initiation rate and pit growth probability, which implied that the X100 pipeline steel had the lowest pitting susceptibility. Yang Zhao, Ping Liang, Yanhua Shi, Yunxia Zhang, and Tao Yang Copyright © 2015 Yang Zhao et al. 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.