Polarization Resistance Measurements Research Articles

Mechanisms of localized corrosion of carbon steel associated with magnetite/mackinawite layers in a cement grout

AbstractCarbon steel electrodes covered with a specific low‐pH cement grout (pH ~10.7 at 20°C), designed for nuclear waste management applications, were immersed for 30 days in a 0.01‐M NaCl + 0.01‐M NaHCO3 solution (pH 7 measured at 20°C), in aerated conditions, at 80°C. The corrosion processes were studied by voltammetry and linear polarization resistance measurements while the corrosion product layers were analyzed by µ‐Raman spectroscopy and X‐ray diffraction. Most of the electrodes (75%) suffered from localized corrosion, a phenomenon associated with the formation of a heterogeneous Fe3O4/FeS layer. It is proposed that the mechanisms of the particular corrosion process observed here are associated with galvanic effects, the large magnetite‐covered zone acting as cathode and the locally mackinawite‐covered zones being anodic regions.

Antioxidant Capacity of Dark Red Corn � Biochemical Properties Coupled with Electrochemical Evaluation

Biochemistry coupled with electrochemical approach is employed in a fast, relatively simple, yet highly precise detection of a plant extract antioxidant properties. Antioxidant capacity of dark red corn grains was investigated electrochemically using cyclic voltammetry (CV) on glassy carbon electrode (GC). The linear polarization resistance (LPR) measurements were performed for examining the corrosion inhibitive behavior of polyphenolics on mild steel. The consistent positive correlation (r=0.99) was established between total phenolic and flavonoid contents obtained by CV measurements and spectrophotometric antioxidant assay (DPPH test). Both analyses confirm the high antioxidant activity of tested pigments. Determination of the corrosion inhibition efficiency revealed that the red corn pigments have anti-corrosion effect on mild steels.

Study on the efficiency of CFRP and GFRP in corrosion resistance of rebar embedded in concrete

Efficiency of composite materials like carbon fibre reinforced polymer (CFRP) and Glass Fibre Reinforced Polymer (GFRP) in controlling rebar corrosion is not studied much. In the present study, cylinders of size 300mm height and 100 mm diameter were casted by using CFRP as a wrap and GFRP in powdered form as an admixture in concrete. Anti-corrosive rubber coating is applied all over the rebar. The concrete cylinders are subjected to accelerated corrosion using 0.5M HCl and 3% NaCl solution for a period of 60 days. The corrosion rate was calculated at regular intervals using Half-cell potential, Linear Polarisation Resistance and Tafel plot measurements. The corrosion resistance of all the specimens are compared and the results have shown that both CFRP and GFRP performed well in corrosion resistance at varying levels. The appropriate protection material from corrosion is also proposed.

Protective films of stearic and octadecylphosphonic acid formed by spray coating

Spray coating formation of stearic and octadecylphosphonic acid films for corrosion protection of cupronickel alloy was studied in this work as a more practical alternative to widely studied dip-coating method. Protective properties of organic films formed under various experimental conditions were examined by electrochemical studies in 3% NaCl solution as a corrosive medium. Polarization resistance measurements as well as electro­chemical impedance spectroscopy were employed to follow in time the corrosion behaviour of cupronickel alloy modified by studied organic acids. It was found that among examined experimental parameters, time elapsed between two sprays and number of sprays have the strongest influence on the film stability and its protective properties. This study confirmed that it is possible to form by spray coating the films of stearic and octadecyl­phosphonic acid with protective properties that resemble to those of the films prepared by dip-coating method. Differences in corrosion behaviour of samples protected with stearic and octadecyl­phosphonic acid were attributed to difference in the bond strength between substrate and each organic acid. Studied samples were also examined by the scanning electron microscopy. Fourier transformed infrared spectroscopy studies showed that crystalline structure dominates in studied films, while contact angle measure­ments confirmed that modified cupronickel alloy surface exhibits hydrophobic properties.

Effect of Cr3+- based conversion films on the corrosion behaviour of electrodeposited composite ternary zinc alloys with embedded carbon nanotubes

ABSTRACTComposite ternary zinc-based alloys Zn-Ni-P and Zn-Fe-P containing embedded multi-walled carbon nanotubes (CNT) were obtained electrochemically. They were treated additionally in an environmentally friendly chemical conversion solution for passivation based on Cr3+-compound. The surface morphology, chemical and phase composition of the coatings after their treatment in the passivating solution were determined by SEM, EDS and XRD analysis respectively. The corrosion behaviour of composite alloy deposits both with or without additional conversion film (CF) was investigated in a model corrosion medium of 5% NaCl using selected methods such as potentodynamic polarisation (PD) curves, electrochemical impedance spectroscopy (EIS) and polarisation resistance (Rp) measurements. The changes in the surface morphology and phase composition of the corrosion tested samples were determined by SEM and XRD analysis. The corrosion studies indicated that the presence of a CF leads to a delay in the anodic dissolution process during the polarisation.

A minimalist approach to polarization resistance measurements in a reinforced concrete structure

AbstractIn the curriculum of future civil engineers, electrochemical concepts are often neglected, even though this knowledge is essential to adequately maintain reinforced concrete structures in a chloride‐exposed environment. Experiments are necessary to consolidate key theoretical concepts, but laboratory experience often involves complex and expensive electronic equipment that may obscure the basic procedures at work. This paper presents a simple minimalistic electrochemical test for polarization resistance measurements by which students can learn basic concepts of corrosion electrochemistry and estimate the corrosion rate as a key parameter for estimation of the remaining service life of concrete structures. The focus is on avoiding unnecessary complications and providing an experiment that can be readily implemented for a wider student reach.

Вплив числа електродних пар на похибку електрохімічного давача поляризаційного опору для вимірювання шидкості атмосферної корозії

Investigate the influence of the number of electrode pairs of multi-electrode co-surface electrochemical polarization resistance sensors on the error of measurement of polarization resistance, and, accordingly, on the corrosion rate under atmospheric conditions. Method of polarization resistance. Determination of the contact area of electrodes with the aluminum substrate by the method of obtaining a print on a flat surface. Graphical modeling of the contact surface of the sensing element from the steel electrodes to the anodized aluminum substrate. Investigation results of the influence of the electrode pairs number of multielectrode cosurface electrochemical polarization resistance sensor, sensing element of which is steel-made and is located on the thermoconductive anodized aluminum substrate, on the measurement error of corrosion rate in atmospheric conditions are presented. It was shown that in determining of the corrosion rate by polarization resistance method the increasing of the electrode pairs number of sensor from one to four increases the reproducibility of measurement results and their convergence with the gravimetric data. Taking into account the form of prints of four-pair sensitive element, the area of surface contact of sensitive element of eight-pair sensor with aluminum substrate was graphically simulated. It was taken into account during modeling, that the design feature of the sensor is a possibility of full contact of one pair of the electrodes with the substrate, which explains the reason of measurement error increasing with increasing the number of electrodes’ pairs. Increasing the pairs number from one to four and then to eight decreases the part of surface of sufficiently tight contact of sensitive element with aluminum substrate from 100% to 50% and further up to 30 %. The extreme dependence of the measurement error on the number of electrodes pairs due to the increasing area of the working surface of the electrodes and reducing the area of tight contact with the aluminum heat-conducting base was revealed. It was found that four electrodes pairs for the presented sensor design is optimal. It was established that the reason of increasing of the error of polarization resistance measurement under atmospheric conditions and, accordingly, the corrosion rate, by using the electrochemical multi-electrode co-surface sensors of polarization resistance under increasing the electrode pairs number (from one to eight) is the decreasing in the surface part of a sufficiently dense contact of the sensitive element (about two or three times). Another tendency that leads to decreasing in error is decreasing in the error of setting the corresponding polarization while increasing the total area of the electrodes. The extreme dependence of this error on the number of electrode pairs with a minimum for a four-pair sensor is shown. The problem of uncontrolled variation of the measurement error by using the polarization resistance sensor of the considered construction was solved and the optimal number of electrode pairs (four) was determined. Using such of a sensor will allow to evaluate the corrosivity of the atmospheric air environment with respect to the responsible metal structures and their corrosion state in local corrosion-dangerous places with stable and minimal error.

A new perspective on measuring the corrosion rate of localized corrosion

AbstractMany corrosion phenomena are nonuniform, which means that anodic and cathodic locations are spatially separated. An example is macrocell corrosion of steel in concrete. Under these conditions, determining the corrosion rate from polarization resistance measurements and using the Stern–Geary equation is fundamentally not possible. We present a novel theoretical approach for the interpretation of galvanostatic pulse measurements, to make them applicable as a method for corrosion rate measurements in situations of localized corrosion. Experiments show that it is important to consider that (a) only a fraction of the applied current flows through the anode of the macrocell, and (b) this current is not constant over time. We propose an approach to quantify and consider these two effects, based on information generally accessible in condition assessment of concrete structures. Our results show that galvanostatic pulse measurements are a robust method to determine the corrosion current. With the traditional empirical approach, the measurement error was generally below factor 3, and occasionally up to factor 10. With the novel approach, this error could be reduced to a factor of maximum 2 in all cases.

Effects of cleaning procedures on the long-term corrosion behavior of bronze artifacts of the cultural heritage in outdoor environment.

The cleaning of metallic artworks is a crucial step for their preservation. Cleaning operations generally aim at removing deposits and corrosion layers, and all the non-stable and potentially reactive phases formed as a consequence of the interaction of the metal with the environment. Thus, all secondary-formed compounds and layers that can undermine the overall preservation of the artwork, both from the esthetic and the corrosion point of view, should be removed. On the other hand, superficial stable patinas contributing to the artistic and historic value of the objects and that may provide protection to the metallic surface should be preserved. The optimal cleaning procedure should be able to promote a long-term improvement of the corrosion resistance of the surfaces. Therefore, the long-term monitoring of the corrosion behavior of the cleaned surfaces with electrochemical techniques could provide valuable information for the selection of the optimal methodology. In this work, five cleaning procedures have been applied to five bronze sculptures. The cleaned surfaces have been characterized following a multi-analytical and non-invasive approach, and the long-term evolution of their corrosion behavior has been monitored by means of on-site non-invasive linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements for more than 2years.

A Novel Electroactive Imide Oligomer and Its Application in Anticorrosion Coating.

A novel aniline tetramer (AT) capped electroactive imide oligomer (EIO) for metal corrosion protection was successfully synthesized in this study. The chemical structure of the EIO was characterized by liquid chromatography-mass spectrometry and Fourier-transform infrared spectroscopy. Furthermore, the redox behavior of EIO was identified using electrochemical cyclic voltammetry studies. An EIO coated on a cold-rolled steel (CRS) electrode was found to possess superior corrosion resistance to polyimide (PI) on a series of electrochemical corrosion measurements in 3.5 wt.% NaCl solution over an extended period (30 days). The mechanism for the advanced corrosion protection of the PI coating on the CRS electrode could be attributed to the redox catalytic capabilities of the AT units present in the EIO. These capabilities may induce the formation of passive metal oxide layers on the CRS electrode. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to analyze the surface condition of the CRS after the corrosion test. EIO- and PI-coated electrodes were identified by a series of electrochemical measurements, including corrosion potential (Ecorr), polarization resistance (Rp), and corrosion current (Icorr) measurements, along with electrochemical impedance spectroscopy (EIS).

Corrosion Behavior of Carbon Steel in Alkaline, Deaerated Solutions: Influence of Carbonate Ions

The corrosion behavior of carbon steel was investigated in deaerated, moderately alkaline conditions (pH 9.8) at room temperature. This study was mainly focused on the influences of carbonate and bicarbonate ions, exposure time, and scale formation on the corrosion rate. The corrosion rate was calculated from Linear Polarization Resistance (LPR) measurements, Electrochemical Impedance Spectroscopy (EIS), analyzing Potentiodynamic Polarization (PDP) curves, and based on time-resolved dissolved iron concentration measurements through Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Surface characterization of corrosion products was performed by means of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). The results showed that the presence of carbonate and bicarbonate significantly modified the corrosion behavior of the steel electrodes and gave rise to corrosion rates of several hundreds of μm y−1, over time decreasing to levels around 100–200 μm y−1. This decrease in corrosion rate was related to scale formation that introduced a certain degree of mass transport limitations. Nevertheless, the corrosion rates remain relatively high, which has implications for engineering. To explain these high corrosion rates, a mechanistic model was proposed, including two combined effects: a chemical and an electrochemical effect. The different methods to determine corrosion rates were found to yield comparable results.

Corrosion Protection of Steel by Volatile Corrosion Inhibitors: Vapor Analysis by Gas-Diffusion Microextraction and Mass Loss and Electrochemical Impedance in NaCl Deliquescence Tests

A new methodology using gas-diffusion microextraction (GDME) was developed for the analysis of volatile corrosion inhibitors (VCIs). The evaluation of the inhibition efficiency and corrosion rate (ν) was performed by NaCl deliquescence tests and correlated with measurements of polarization resistance (Rp) obtained from electrochemical impedance spectroscopy (EIS) analysis and with the pH resulting from the atmosphere of the inhibitor (pHGDME). The correlation obtained between n and pHGDME indicates that the higher the value of pHGDME the lower the corrosion rate. The Raman spectra of steel was used to monitor in situ adsorption of VCI and the surface modifications caused by the inhibitors. The scanning electron microscopy (SEM) images corroborate the data of ν, both indicating that the cyclohexylamine vapor showed the best corrosion resistance performance.

The Effect of Acid Pickling on the Corrosion Behavior of a Cerium Conversion-Coated AA2198-T851 Al-Cu-Li Alloy

The effect of acid pickling pretreatments prior to cerium conversion coating process on the corrosion behavior of AA2198-T851 alloy substrates was investigated. Three acid pretreatments were employed: nitric acid (HNO3), phosphoric acid (H3PO4) and sulfuric acid (H2SO4). The cerium conversion coating process was performed using a batch solution composed of cerium nitrate and hydrogen peroxide. Microscopic techniques, electrochemical impedance spectroscopy, polarization resistance and open-circuit potential measurements were employed to investigate the effect of each acid pretreatment. The untreated and nitric acid pretreated substrates presented more defective cerium conversion layers than the substrates treated with phosphoric and sulfuric acids. Accordingly, the corrosion resistance of the untreated and nitric acid-treated substrates was very low, while that of the substrates treated with phosphoric acid and sulfuric acids were greatly improved. The sulfuric acid pickling treatment was the best pretreatment before cerium conversion coating among the investigated pretreatments on the AA2198-T851 Al-Cu-Li alloy.

Effect of GGBS and chloride on compressive strength and corrosion performance of steel in fly ash-GGBS based geopolymer concrete

This study investigates the effect of GGBS on strength and corrosion performance of steel in chloride contaminated fly ash-GGBS based geopolymer concrete (GPC). Fly ash and fly ash-GGBS based GPC mixes were added with 0% and 3.5% of NaCl during the time of preparation. Corrosion potential measurement and corrosion current density by linear polarization resistance (LPR) measurement were performed on reinforced cylindrical GPC specimens. Results indicated that the fly ash-GGBS based GPC showed higher compressive strength as compared to fly ash based GPC, due to formation of N-(C)-A-S-H and C-S-H gel in fly ash-GGBS based GPC which is evident from FESEM analysis. The chloride admixed GPC mixes achieved lower compressive strength than that of control (0% NaCl) GPC mixes. There was a higher probability of corrosion initiation and higher corrosion current density of steel reinforcement in NaCl added GPC as compared to the control GPC.

Risk of failure in existing RC balcony and strength verification under degradation phenomena

In the present paper, the safety conditions of reinforced concrete (RC) balconies subject to degradation phenomena caused by carbonation, presence of chlorides or water infiltration were examined. After a brief review of the typical damages of balconies occurring with detachments of plaster and bricks expulsion, some cases of collapses of balconies recently occurred were presented.Therefore, a calculation model was proposed for a hand verification of the flexural and shear strength of existing corroded T beams cast in place of lightened RC orthotropic slabs forming the balcony and for the calculus of deflection including slippage of steel bars. Diffused and pitting corrosion on steel bars, compressive concrete strength degradation, and concrete bond strength degradation are included in the model. This approach is simple and can be applied based on the experimental information available (carbonation test, chloride content, measurement of the pitting in the bar, a gravimetric method for general corrosion) or by utilizing analytical expressions calibrated on knowledge of the corrosion current intensity determined by linear polarization resistance measurement (LPR).

An Exemplar Imidazoline Surfactant for Corrosion Inhibitor Studies: Synthesis, Characterization, and Physicochemical Properties

AbstractAn optimized one‐pot recipe has been developed to synthesize a surfactant molecule, referred to as OMID, consisting of an imidazoline head group and aliphatic tail, which is an exemplar corrosion inhibitor for carbon steel in acidic solutions. As evidenced by gas chromatography, 1H and 13C nuclear magnetic resonance, and Fourier‐transform infrared data, a high‐purity product was achieved without the use of either a solvent or catalyst. Critical micelle concentration values and corrosion inhibition efficiencies ( η%) were determined in aqueous solutions of hydrochloric acid and sulfuric acid using surface tensiometry and linear polarization resistance measurements, respectively. Hydrolysis of the imidazoline head group as a function of pH (0–11) was explored with ultraviolet–visible absorption spectroscopy. In addition, N 1s and C 1s X‐ray photoelectron spectroscopy data were acquired from both surface‐adsorbed OMID and a multilayer of the imidazoline head group of OMID. These latter data are highly relevant to those attempting to understand OMID inhibition chemistry.

Investigation of corrosion behaviour of carbon nanotubes coated basalt fabric as a reinforcement material

In this study, the corrosion behaviour of carbon nanotubes (CNTs) coated basalt fibre (BF) (BFCNTs) obtained by chemical vapour deposition (CVD), was studied. During CVD, the CNTs were grown on BF, (a) at different growth temperatures and (b) for different growth times. The physicochemical measurements were performed using X-ray diffraction, Raman spectroscopy, and field-emission scanning electron microscopy. The corrosion performances were investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic sweep (PDS), linear polarization resistance (LPR) and weight loss measurements. The BFCNT prepared at 650 °C for 120 min exhibited the best corrosion stability during the prolonged exposure to 0.1 M NaCl electrolyte. The outcomes of this study would be useful in designing the carbon nanotubes coated basalt fibre with the best corrosion resistance.

Nitrogen‐based corrosion inhibitor film study using weight loss and electrochemical methods in static and turbulent conditions

AbstractThere is an increasing demand from oil and gas industry to ensure the integrity of assets and the enviroment in the critical conditions found in presalt wells. This study evaluates new formulations of corrosion inhibitors with different types and alkoxylation degrees of nitrogen‐based inhibitors to assess corrosion behavior of carbon steel (API X65). For these studies, corrosion rates were determined through measurements of weight loss and linear polarization resistance (LPR). In the case of electrochemical measurements, experiments were carried out in a laminar flow and in a turbulent flow regime. All data were collected in the presence of CO2 and CO2/H2S mixtures. The results revealed that corrosion protection of carbon steel critically depends on the nitrogen‐based inhibitor's alkoxylation type and degree as well as the condition to which they are exposed. It was possible to notice that an ethoxylated amine whose inhibition efficiency in the presence of CO2 was about 10%, when exposed to H2S environment at the same temperature showed an efficiency of 86%. It was also observed that the inhibitor with a higher ethoxylation degree presented better efficiencies than the one with a lower degree.

Mild steel protection with tannic and polyaspartic acid in cooling systems

Purpose Tannic acid (TA) is one of the green corrosion inhibitors for mild steel; its anti-corrosive performance in alkaline water on mild steel when it is used together with polyaspartic acid (PASA) still has not been investigated. The purpose of this study is to develop an effective, biodegradable and environment-friendly novel corrosion inhibitor based on TA and PASA as an alternative to the conventional inorganic inhibitors for mild steel in decarbonised water, which is common in cooling systems. Design/methodology/approach Corrosion inhibition mechanism is investigated by electrochemical techniques such as polarisation measurements and electrochemical impedance spectroscopy, and results were evaluated to determine the optimum inhibitor concentration for industrial applications. Additionally, practice-like conditions are carried out in pilot plant studies to simulate the conditions in cooling systems. Thus, the efficiencies of the inhibitors are evaluated through both weight loss and linear polarisation resistance measurements. Moreover, the corrosion product is characterised by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and Fourier-transform infrared spectroscopy (FTIR) analysis. Findings TA shows high inhibition efficiency especially towards pitting corrosion for mild steel in decarbonised water. PASA addition in the cooling systems improves the inhibition efficiency of TA, and at lower concentrations of TA + PASA, it is possible to obtained better inhibition efficiency than TA alone at higher inhibitor amounts, which is essential in economic and environmental aspect. Originality/value A blended inhibitor program including TA and PASA with suggested concentrations in this work can be used as an environmental friendly treatment concept for the mild steel corrosion inhibition at cooling systems.

(Invited) Measurement of Polarization Resistance of LSM + YSZ Electrodes on YSZ Using AC and DC Methods

Most of the measurements of electrode polarization are conducted using electrochemical impedance spectroscopy (EIS). The electrochemical devices, however, operate in a DC mode. Thus, frequency-dependent circuit elements (capacitances, constant phase elements, inductances) have no significance on the actual operating current and voltage of a device. The objective of the present work was to measure electrode polarization resistance using both EIS and DC technique and compare the results. A solid cylinder of 8YSZ of diameter ~1.17 cm and length ~5.00 cm was made by powder pressing in an isostatic press using a polymer mold and sintering at 1600oC in air for 4 h. Platinum electrodes/probes were painted along the circumference at four places approximately 1.2 cm apart. The strip width was ~2 mm. The sample was fired at 900oC. LSM + YSZ electrodes were applied on the two circular end faces and fired at 1000oC for 2 h. Pt wires were attached to the four Pt electrodes. Gold mesh was adhered to the circular LSM + YSZ electrodes. The sample was secured in a ceramic fixture and placed in a tubular furnace. Measurements were conducted in O2-N2 gas mixtures containing 100%, 10%, 5% and 1% O2. For DC studies, a DC voltage was applied in the range of 0.05 V and 0.38 V across the sample. At each applied voltage, the corresponding current was measured and potentials at all four probes was measured. From the measured potentials and the current, the ionic resistance of the cylinder was determined, from which the ionic resistivity was determined. From the voltage measured between one of the end electrodes and a probe, the ionic resistance between the end electrode and the probe, and the net current density, overpotential at the electrode was determined. This was done as a function of current. Also, from these measurements, electrode polarization resistance was determined. For EIS studies, done only under no applied DC voltage, spectra were obtained between electrode-1 and probe-2 and between probe-2 and electrode-2. From these measurements, the polarization resistances of the two electrodes were determined separately. EIS spectra were also obtained across electrode-1 and electrode-2. The spectra across electrode-1 and probe-2 and across probe-2 and electrode-2 were summed point by point. These spectra were then compared with the spectra across the entire sample.