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Reinforcing steel bars in concrete structures exposed to tropical marine atmospheres experience very high corrosion rates due to several environmental factors. The aim of this research was mainly to elucidate if zinc‐coated rebars may delay the onset of corrosion and/or extend the service life of infrastructure in the tropics, as the approach is promising in other atmospheres.

Hot‐dip zinc‐coated and plain steel rebars were embedded in concrete cylinders made with local aggregates and having four different water‐to‐cement ratios. Samples were exposed during 24 months at the marine breeze in a coastal site in the Gulf of Mexico. The corrosion behaviour of zinc‐coated and uncoated rebars was monitored by means of corrosion potential and linear polarization resistance techniques. Also, carbonation penetration and the chloride ingress were measured and correlated with the corrosion behaviour.

Only under the worst case conditions (concrete with 0.7 w/c ratio) did galvanized steel experience corrosion initiation. It was shown to resist higher chloride levels than uncoated steel and extended the onset of corrosion.

The effectiveness of the zinc‐coated bar for corrosion control is controversial and its use mainly is supported by accelerated tests or application in cold or subtropical environments. This research showed the corrosion behaviour in an extremely corrosive tropical zone.

The purpose of this paper was mainly to select one of the three types of coatings for protection of steel used as reinforcement in composite pipes (thin steel shell covered by cement-mortar) subjected to chloride exposure. To achieve this target, an attempt was made to develop a simple methodology for evaluating the performance of corrosion protection measures in terms of chloride threshold level (CTL) and corrosion initiation time (TI).

Bare, epoxy, red oxide and zinc primer-coated steel strips were embedded in cement mortar with sand/cement and water/cement ratios of 2 and 0.5 (by mass), respectively, to prepare the specimens which were exposed to chloride solution having a high concentration of 10 per cent NaCl. For determining the amounts of the water-soluble chloride diffused inside the specimens, powdered samples of mortar were collected from two different depths from the exposed surface of specimens on completion of each of the four different exposure times. The corrosion current densities were determined at two different stages. A step-by-step procedure for calculating CTL and TI using the measured chloride contents and corrosion current densities was established with the help of relevant information available in the literature.

Based on the comparison of the values of CTL and TI calculated for bare steel and steel with all three types of coatings, utilizing the experimental data and the proposed calculation procedure, the epoxy-coated steel was found to have the best performance.

This research has resulted into development of a simple methodology for evaluation of the performance of protective measures against corrosion of steel embedded in mortar or concrete exposed to chloride-bearing environment.

The purpose of this research is to study different extra-heavy crude oil-in-water emulsions that can be found in practice for corrosion process of X52 steel adding 60 mg.L-1 of non-ionic surfactant and a corrosion inhibitor (CI). Electrochemical impedance spectroscopy and Tafel plots are carried out. Thus, Bode-modulus and Bode-phase angle plots are discussed. Adsorption isotherms obtained from corrosion rate (CR) values are taken into account.

Two-electrode arrangement is used to characterize the pseudo-capacitance values for X52 steel exposed to water and crude oil phases, mainly. Electrochemical evaluations for X52 steel exposed to extra-heavy crude oil-in-water emulsions are recorded in a conventional three-electrode cell to study the corrosion process as was documented in detail by Quej-Ake et al. (2015). Therefore, all electrodes are placed as close as possible to eliminate the iR-drop.

Pseudo-capacitance analysis shows that X52 steel immersed in oilfield produced water was more susceptible to corrosion than that immersed in ocean water solution and extra-heavy crude oil phase. After being analyzed, the X52 steel surface coverage and adsorption process for surfactant and CI could be concluded that surfactant could protect the metal surface. In a coalescence extra-heavy crude oil-in-water emulsion, the water medium generated a new solution that was more corrosive than the original water phase. Wash crude oil process was provoked in emulsion systems to sweep up the salts, mainly. Thus, corrosive species that can be recovered inside extra-heavy crude oil may appear, and in turn a new more corrosive solution could be obtained. Taking into account the straight line obtained in Bode-modulus plot for X52 exposed to extra-heavy crude oil, it is possible to point out that the negative value of the slope or R² can be related to a coefficient (Jorcin et al., 2006). It is important to mention that electrochemical responses for X52 steel exposed to extra-heavy crude oil-in-water under coalescence emulsions revealed that corrosion and diffusion processes exist. Therefore, a possible good inhibitor is surfactant in emulsion systems.

CR and anodic and cathodic slopes suggest that the surfactant acted as mixed CI. Of these, susceptible anodic (MnS and perlite or cementite) and cathodic (ferrite) sites on steel surface could be affected, due to which physicochemical adsorption could happen by using electrochemical parameters analysis. Thus, no stable emulsions should be taken into account for extra-heavy crude oil transportation, because corrosion problems in atmospheric distillation process of the crude oil due to stable emulsion cannot be easily separated. In this manner, coalescent emulsions are more adequate for transporting extra-heavy crude oil because low energy to separate the water media is required.

The purpose of this work is to study the corrosion rate of X52 pipeline steel exposed to three types of soils collected in Campeche State in México. The electrochemical evaluation for X52 steel exposed to soils ranging from saturated soil until dry conditions was carried out for a period of 21 days. Owing to its versatility to study the steel corrosion process exposed to different types of soils, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry tests were performed. Additionally, optical and electronic microscopy observations of the steel surface were carried out.

Electrochemical cell arrangement was described elsewhere (Quej-Ake et al., 2014). Owing to soil being an electrolytic system with high resistivity and impedance, all electrodes were placed as close as possible, and iR-drop compensation was taken into account using two rods of graphite as an auxiliary electrode. In addition, the conductivity of the soil (R_s) obtained from EIS was used to correct the potential of the working electrode according to iR-drop, and an analysis of ohmic drop from the polarization curves was carried out.

Saturated conditions of the three soils were initially considered as the most corrosive conditions for X52 steel surface. Finally, 21 days of immersion time was taken into account as the more drastic condition. So, according to results, X52 steel exposed to beach sand was more susceptible to the corrosion process (0.092 mm/year). iR corrected was negligible at low over-potentials region in saturated soils, which is inside the linear region of Tafel or the activation region. In addition, high cathodic peak potential value obtained from cyclic voltammetry for X52 steel exposed to saturated soil may be attributed to hydrogen evolution reaction and neutral pH.

The paper has implications for research. It bridges the gap between theory and practice.

Cyclic voltammetry is a really important tool for the electrochemical analysis of the pipeline steel surface exposed to saturated soils, but is not adequate for analysis of steel exposed to dried soils. In addition, the physicochemical results show that fissures, voids and extra-oxygen presence could also affect the electrochemical responses obtained for X52 steel exposed to soils.

The purpose of this paper is to investigate the influence of Cl‐ions on the pitting corrosion of water‐wall tube of a boiler and the principle behind it.

The specimens were immersed for seven hours at 300°C in deaerated water subjected to simulation‐modified equilibrium phosphate treatment, containing Cl‐ions at various concentrations. The effects of Cl‐ions on pitting corrosion were assessed by the rate mass loss, transmission reflection metallurgical microscopy, SEM, EDS, and XRD.

The results indicated that Cl‐ions cause the breakdown of passive films. The corrosion mechanism of Cl‐is proposed to involve an intermediate dissolution stage. The Cl‐ions act as a catalyst of corrosion, by inducing the hydrolysis of Fe2+. The critical susceptive Cl‐concentrations are 0.2 and 0.6 mg·L^‐1 for the passivated specimens and for the unpassivated specimens, respectively.

The paper provides information regarding the relationship between Cl‐concentrations and pitting corrosion, useful for understanding the mechanism of Cl‐induced pitting corrosion, and the research results can provide theoretical guidelines for preventing water‐wall of power plants from corroding.

The purpose of this paper is to investigate the inhibitive properties of black pepper extract (BPE) for aluminium in 1M hydrochloric acid (HCl) medium.

Gravimetric, electrochemical impedance spectroscopy, galvanostatic polarization, scanning electron microscopy with energy dispersive X-ray examinations (SEM-EDX) techniques were used to study the corrosion inhibitive study.

The gravimetric measurement indicates that inhibition efficiency shows direct proportional relation with concentration of inhibitor. The impedance results illustrates that there was a presence of protective layer of inhibitor adsorbed on the metal/solution interface. Polarization outcome showed that BPE is mixed type inhibitor. The existence of adherent layer of inhibitor on the Al surface was confirmed by SEM-EDX. Quantum chemical calculations were performed using the density functional theory at B3LYP/6-31G(d) level of theory to evaluate the activity of inhibitor molecules present in extract towards the corrosion inhibition of Al.

Due to the presence of large number of compounds in the extract, it becomes difficult to understand the most active compound responsible for inhibition. However, from gas chromatography mass spectrometry and quantum data, the approximation has been made that the major compound piperine present in the extract can be most probable component responsible for the inhibition activity. Further calculation of binding energy between Al and inhibitor molecules can be performed using Material Studio software.

The extract can be used in cleaning and etching solutions. It can be used to limit the loss of Al metal during etching process.

BPE can be used as a potential source of eco-friendly corrosion inhibitor for Al in HCl medium.

Besides with a large amount of Na⁺ and Cl⁻ ions in seawater, the presence of Mg⁺² and SO₄⁻² ions builds more complex corrosion mechanism. This paper aims to investigate the corrosion of embedded reinforcement in concrete with the environment of both Cl⁻ and SO₄⁻² anions associated Mg⁺² cation.

The concrete specimens were prepared by using ordinary Portland cement (OPC), and OPC blended with metakaolin (MK) for water to cementitious material ratio (w/cm) 0.48 and 0.51. The concrete mixes were contaminated with the addition of MgCl₂ alone and combined MgCl₂ and MgSO₄ in mix water. Reinforcement corrosion was evaluated by half-cell potential and corrosion current densities (I_corr) at regular intervals. Moreover, the influence of cementitious material type, salt type and w/cm ratio on electrical resistivity of concrete was also investigated. The statistical models were developed for electrical resistivity as a function of calcium to aluminium content ratio, compressive strength, w/cm ratio and age of concrete.

Although the corrosion initiation time increases in the concomitant presence of MgSO₄ and MgCl₂ as internal source compared to MgCl₂, I_corr values are higher in both OPC and MK blended concrete. However, electrical resistivity decreased with addition of MgSO₄. MK blended concrete performed better with increased resistivity, corrosion initiation time and decreased I_corr values.

This study reports statistical distributions for scattered I_corr of rebar in different concrete mixtures. Stepwise regression models were developed for resistivity by considering the interactions among different variables, which would help to estimate the resistivity through basic information.

Using organic coatings serves as a key method to protect metal structures against corrosion. Attempts have been made to improve the corrosion inhibition of the coatings using novel types of pigments. This study aims to study the application of organic coatings containing rice straw (RS) waste as anticorrosive pigment for corrosion protection of reinforced steel. The RS was used by precipitating a thin layer of ferrite pigments on its surface to improve their characteristics and corrosion resistance activity.

The evaluation of corrosion behavior of coated reinforced steel with paints containing these novel pigments is reported using different electrochemical methods.

The coatings containing the new prepared RS-ferrite pigments offered good corrosion protection, and coatings containing RS-ZnFe showed the best protection performance.

This paper introduces novel method to prepare treated RS without any burning and to play the role of pigments in anticorrosive paint formulations based on its silica content.

The purpose of this paper is to investigate the interfacial conductivity and corrosion resistance of the Ni–P/Ti₄O₇ composite coating that is deposited on a carbon steel substrate as bipolar plates for proton exchange membrane fuel cells.

The Ni–P/Ti₄O₇ coating was prepared by electroless plating. Scanning electron microscopy, white light interference, energy dispersive spectrometry and X-ray diffraction were used, respectively, to study the surface morphology, chemical composition and phase composition of coated samples. Electrochemical impedance spectroscopy, potentiodynamic and potentiostatic polarization were used to test the electrochemical performance and corrosion behavior. The interfacial contact resistance (ICR) was measured via the standard method.

The surface of the Ni–P/Ti₄O₇ coating is complete and dense and without obvious defects. The electrochemical test results show that the Ni–P/Ti₄O₇ coating provides better corrosion resistance than the Ni–P coating and substrate. Compared with the Ni–P coating, the ICR of the Ni–P/Ti₄O₇ coating is lower by about 82.7%. This is because the coating has more conductive contact points. The more exciting thing is that the ICR of the Ni–P/Ti₄O₇ coating only increases to 12.38 mΩ·cm² after 5 h of polarization.

This paper provides a method for achieving surface modification of metal bipolar plates. Introducing Ti₄O₇ particles in the Ni–P layer reduces the contact resistance before and after polarization while ensuring good corrosion resistance.

The corrosion performance of zinc deposits when alloyed with d‐metals like nickel and cobalt was evaluated with special reference to heat treatment effects by conventional electrochemical methods such as potential‐time measurement and EIS. Immersion tests were also performed to substantiate the above results. The sacrificial ability of heat treated alloy deposits was examined in the context of protecting steel structures by galvanic coupling. The corrosion performance of the alloy deposits, obtained from the newly developed citrate‐based sulphate bath, was investigated in the neutral medium for instance, 3.5 per cent NaCl solution. XRD technique was employed to ascertain the desired phase formation of the alloy structure and the elemental analysis was performed by means of EDAX analyser in order to substantiate the XRD findings. Light microscopic examination was carried out on the deposits with and without heat treatment in order to study the surface character of these deposits. The microstructure of the alloy deposits was also examined by SEM.