Polarization Resistance Measurements Research Articles

The Influence of Corrosion Processes on the Degradation of Concrete Cover.

In this work, two methods were used to accelerate the corrosion of concrete. In the first method, chloride ions were injected into the concrete using the migration method. The moment of the initiation of the corrosion process was monitored using an electrochemical method of measuring polarization resistance. In the next step, the corrosion process was accelerated by the electrolysis process. Changes on the sample surface were also monitored using a camera. In the second method, the corrosion process of the reinforcing bar was initiated by the use of the electrolysis process only. Here, changes occurring on the surfaces of the tested sample were recorded using two web cameras placed on planes perpendicular to each other. Continuous measurement of the current flowing through the system was carried out in both cases. It was assumed that in conditions of natural corrosion, a crack would occur when the sum of the mass loss of the reinforcing bar due to corrosion reached the same value in tcr(real) (real time) as it reached in the tcr (time of cracking) during the accelerated corrosion test. The real time value was estimated for C1 concrete with cement CEM I. The estimated value was tcr(real) = 1.1 years and for C2 concrete with cement CEM III, tcr(real) = 11.2 years. However, the main difference that was observed during the tests was the nature of the concrete cracks. In the case of the C1 concrete sample, these occurred along the reinforcing bar, while in the C2 concrete, the failures occurred on a perpendicular plane transverse to the direction of the reinforcing bar.

Unraveling the structure-property relationship of pyrimidine-derivatives as CO2 corrosion inhibitors: Experimental and periodic DFT investigations

CO2-containing environments commonly cause corrosion of carbon steel (CS) pipelines used in the oil and gas industry. In this work, the inhibition of corrosion by three derivatives of pyrimidine, namely 2-mercaptopyrimidine (MPY), 4-hydroxy-2-mercapto-6-methylpyrimidine (HMMP), and 4,5-Diamino-2,6-dimercaptopyrimidine (DDMP) for C1018 CS in CO2 saturated 3.5% NaCl brine was investigated. The corrosion rates and inhibition efficiency were investigated at 25 and 70 °C using open circuit potential, linear polarization resistance, potentiodynamic polarization and electrochemical impedance measurements. The post-immersion surface characterization of the exposed C1018 CS with and without the three molecules was carried out using SEM and 3D surface optical profilometer. Theoretical computation using DFT was further utilized to examine the role of the molecular structures and the mechanism of inhibition of the three molecules on steel surface at the atomic level. The experimental results indicate the following order of inhibition efficiency: MPY > DDMP > HMMP. Our experimental work proved that MPY molecule (the smaller one with the least number of heteroatoms) as the most efficient corrosion inhibitor. Surface characterization analysis confirmed the order of inhibition efficiency. The theoretical results revealed that the stability of molecules adsorbed on Fe (110) surface in the parallel orientation and on FeCO3 (104) is identical on both surfaces, which is completely consistent with the experiment. Our study provides a feasible strategy for developing new corrosion inhibitors by understanding how similar organic inhibitors work.

Investigation of the inhibiting effect of environmentally friendly cerium-containing conversion films on the corrosion of zinc coatings

In the present work, the inhibiting effect of environmentally friendly cerium and phosphorus-based conversion films on zinc corrosion in 5% NaCl and 1 N Na2SO4 test media was investigated. The films were prepared by immersion and stirring in the passivating/converting solution for time periods of 3,5,7, 10 min., respectively. The chemical composition of the films was determined by EDX analysis. The results of the electrochemical studies showed that in 5% NaCl medium, cerium- and phosphorus-based films exhibited high inhibition effect only during the first days of polarization resistance (Rp) measurement. In 1 N Na2SO4 medium, the Rp of the conversion films was up to 2.5 times higher than that of pure zinc coatings throughout the test period.

A novel methodology for monitoring low-temperature corrosion caused by hygroscopic salts using linear polarization resistance

A new methodology for monitoring low-temperature corrosion caused by hygroscopic salts was developed and tested with ZnCl2. First, deliquescence and efflorescence points of ZnCl2 were determined by electrochemical impedance spectroscopy and chronoamperometry measurements in the range of 10–35 vol % H2O. Then, low-temperature corrosion was monitored using a probe that combines linear polarization resistance and mass loss measurements. Suitable potential and scan rate for the linear polarization resistance measurements were experimentally determined. The feasibility of the probe was tested by monitoring the corrosiveness of ZnCl2 on P235GH steel under different temperatures (100–180 °C) and water vapor concentrations (15–35 vol %). With the developed corrosion probe, corrosion caused by hygroscopic salts during changes in testing conditions can be monitored and evaluated.

The Influences of Traces of Oxygen and Sulfide on the Corrosion of Copper Under Canadian Nuclear Waste Disposal Conditions

The Canadian repository concept for the permanent disposal of used nuclear fuel is to seal it in Cu-coated steel containers and dispose of it in a deep geological repository (DGR) surrounded by compacted bentonite clay. The Cu coating will be directly bonded on the steel vessel and lid using electro-deposition (ED-Cu), with the final container closure weld sealed with a cold-sprayed Cu deposit (CS-Cu). To assess the durability of such a container, long-term corrosion experiments have been performed on CS-Cu and ED-Cu specimens, and compared with those performed on wrought Cu specimens provided by the Swedish Nuclear Fuel and Waste Management Company (SKB-Cu).Experiments were conducted in 3 M NaCl solutions containing traces of sulfide (< 10- 6 M) for exposure periods of ≥150 days. These conditions reflect a generic groundwater that may influence container corrosion in a Canadian DGR Since conditions in a DGR will evolve from initially oxic to eventually anoxic, experiments were conducted under three sets of redox conditions: (i) aerated (oxic) conditions; (ii) Ar-purged (oxic to anoxic transition conditions (with a dissolved [O2] ~ 10- 6 M)); and (iii) anaerobic chamber (anoxic) conditions ([O2] < 1.3 × 10- 9 M). The exposure process was followed using open circuit (i.e., corrosion) potential and polarization resistance (RP) measurements. Specimens were analyzed before and after corrosion using optical microscopy, scanning electron microscopy on surfaces and focused ion beam cut cross sections, Raman spectroscopy, and X-ray photoelectron/Auger spectroscopy.In all environments, all three types of specimens (ED-Cu, CS-Cu, SKB-Cu) showed similar behaviour. Under anoxic conditions, minor corrosion, indicated by large RP values, leading to the deposition of traces of chalcocite (Cu2S) (identified by Raman spectroscopy) and observed by SEM, indicated that corrosion could be attributed to reaction with the trace amounts of sulfide present in NaCl. In Ar-purged solutions, the RP values were approximately one order of magnitude lower (i.e., the corrosion rate was one order of magnitude higher) than those measured under anoxic conditions, and significant corrosion damage was observed in SEM micrographs. Both Cu2O and Cu2S were detected by Raman spectroscopy. The detection of oxidized sulfur species (SO3 2 - and SO4 2 -) on the corroded surface by XPS/Auger confirmed that even trace amounts of dissolved O2 led to sulfide oxidation and the possible formation of potentially more corrosive species such as thiosulfate (S2O3 2 -). Under aerated conditions, extensive corrosion occurred leading to the formation of green CuII products (atacamite (Cu2(OH)3Cl)) with no detectable Cu2S formation.Within the DGR, corrosion of Cu under anoxic conditions will be limited by the available supply of sulfide, which may be produced remotely at the host rock/clay interface and/or in the porewater within the rock fractures. In the presence of even trace of dissolved O2, the corrosion process is significantly accelerated with the formation of potentially aggressive oxidized sulfur species. Under aerated conditions, extensive corrosion due to reaction with O2 leads to the deposition of CuII deposits. On the time scale of these experiments with only trace of sulfide present, no detectable conversion of copper oxide to Cu2S was observed. Keywords: Copper; Sulfide; Corrosion; Nuclear waste disposal

Understanding the Corrosion of Copper in Nitric Acid By Tuning the Solution Chemistry

The used fuel container (UFC) is a key engineered barrier to permanently contain and isolate used nuclear fuels underground in deep geological repositories (DGR) to be implemented in Canada, Sweden and Finland.1,2 Copper is used for corrosion protection in the current design of the UFC. Within a DGR, radiolysis of humid air will result in the formation of nitric acid.3 Recent studies showed that copper corrodes faster in nitric acid when oxygen is present, which will be the case for a short period after the UFC’s emplacement.4 When the oxygen becomes depleted in a DGR, the corrosion of copper will be minimal but can be affected by corrosion products such as Cu+, Cu2+, NO2 - and NO. Previous results suggest that the presence of copper ions in the solution surrounding the copper can activate nitrate as a cathodic reagent.5 A possible mechanism is that Cu+ reacts with nitrate through its oxidation to Cu2+, which then reacts with metallic copper through its comproportionation reaction, accelerating the corrosion process.5 Yet, a precise mechanistic understanding of the role of Cu+, such as the degree to which oxidation of Cu+ occurs in solution, or if Cu+ simply acts as a catalyst for nitrate reduction or decomposition, is missing. As a result, an improved understanding of the influence of solution parameters on the corrosion mechanisms of copper in nitric acid is needed, including the presence of oxidants and Cu+-chelating species such as chloride.Herein, the interplay between the dissolved redox couples, Cu+/Cu2+ and NO3 -/NO2 - and Cl- is explored, and their effect on the corrosion of copper is studied by linear sweep voltammetry and polarization resistance and Tafel analysis. The interpretation of linear polarization resistance measurements in the presence of multivalent ions and the role of corrosion products are discussed.1 P. G. Keech, P. Vo, S. Ramamurthy, J. Chen, R. Jacklin and D. W. Shoesmith, Corrosion Engineering, Science and Technology, 49, 2014, 425-430.2 F. King, L. Ahonen, C. Taxen, U. Vuorinen and L. Werme, Copper corrosion under expected conditions in a deep geologic repository (SKB-TR--01-23), 2001. Sweden.3 R. P. Morco, J. M. Joseph, D. S. Hall, C. Medri, D. W. Shoesmith and J. C. Wren, Corrosion Engineering, Science and Technology, 52, 2017, 141-147.4 J. Turnbull, R. Szukalo, M. Behazin, D. Hall, D. Zagidulin, S. Ramamurthy, J. Wren and D. Shoesmith, Corrosion, 74, 2017, 326-336.5 J. Turnbull, R. Szukalo, D. Zagidulin, M. Biesinger and D. W. Shoesmith, Materials and Corrosion, 72, 2021, 348–360.

Corrosion-Resistive ZrO2 Barrier Films on Selected Zn-Based Alloys.

This work presents the enhanced corrosion resistance of newly developed two-layer composite coatings deposited on low-carbon steel: electrodeposited zinc alloy coatings (Zn-Ni with 10 wt.% Ni (ZN) or Zn-Co with 3 wt.% Co (ZC), respectively) and a top ZrO2 sol-gel layer. Surface morphology peculiarities and anti-corrosion characteristics were examined using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), atomic force microscopy (AFM), water contact angle (WCA) measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analyses, potentiodynamic polarization (PDP) curves, corrosion potential (Ecorr), polarization resistance (Rp) measurements (for a prolonged period of 25 days) and open-circuit potential (OCP). The results were compared with the corrosion peculiarities of usual zinc coating. The zirconia top coatings in both systems were amorphous and dense, possessing hydrophobic nature. The experimental data revealed an increased corrosion resistance and protective ability of the ZC system in comparison to that of ZN due to its smooth, homogeneous surface and the presence of poorly crystallized oxides (ZnO and Co3O4), both later playing the role of a barrier for corrosive agents.

Corrosion of carbon steel rebar in binary blended concrete with accelerated chloride transport

Samples with two different binary blended concrete mixes were prepared, one containing cement replacement of 50% slag (referred here as SL mix) and the other containing cement replacement of 20% fly ash (termed here as FA mix). The water to cementitious ratio used to produce concrete specimens was 0.41. On the top surface of each specimen, various reservoir lengths that ranged from 2.5 cm to 17.5 cm were fitted, and these reservoirs were filled with a 10% NaCl solution. Electromigration was used to accelerate the transport of chlorides, with an applied potential of 9 V at first, and subsequently reduced to 3 V after about a week. The electromigration was applied for a short period (few weeks to a couple of months). For a period of about 1100 days, the corrosion related parameters such as concrete solution resistance, rebar potential, and corrosion current were monitored via the rebar potential measurements, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements, the latter used only to obtain the solution resistance. The corrosion current values determined through experimental observations were then converted to mass loss using Faraday’s law. The readings of corrosion current values (last 7 sets of readings) as well as the calculated mass loss values were found to be larger for the rebars embedded in specimens prepared with SL mix, followed by rebars embedded in specimens prepared with FA mix. Corrosion current and calculated mass loss values in general tended to increase with increasing solution reservoir lengths. No cracks or corrosion products that reached the surface of the concrete were observed on the specimens for the duration of the reported monitored propagation period. This study offers a framework for future studies on accelerated steel corrosion in concrete.

Electrochemical Study of Corrosion Inhibition of Carbon Steel During Oil/Water Intermittent Wetting

Application of corrosion inhibitors in production systems containing oil and water is an economic method to protect carbon steel against internal corrosion. This study investigates how intermittent oil/water wetting of such a steel surface, simulating multiphase flow phenomena, impacts corrosion inhibition in exploration-production (high salinity with CO2) and refinery (low salinity without CO2) environments. The employed corrosion inhibitor was a pyrimidinium-type model compound, its effectiveness against corrosion being characterized using linear polarization resistance measurements and electrochemical impedance spectroscopy. Experimental results demonstrated that the presence of an aliphatic oil promotes corrosion inhibition in the exploration production condition, but failed to do so in the refinery condition. Electrochemical impedance spectroscopy revealed two different protection mechanisms in the presence of oil between the two environments. The inhibitor layer in refinery condition with oil was different from in the simulated exploration production environment after oil wetting. Results also demonstrated that the inhibitor in this study was physically adsorbed on the surface steel via electrostatic attraction. Anions, identified as chloride ions, played a critical role in inhibitor adsorption.

Impedance analysis of electrolyte processes in a solid oxide cell

AbstractElectrochemical impedance spectroscopy and the distribution of relaxation times are powerful tools to study polarization processes in solid oxide cells (SOC). Commonly the measured polarization resistance is solely attributed to polarization phenomena in the electrodes whereas the electrolyte is assumed to act as purely ohmic series resistance.In this study an electrolyte supported SOC is investigated by impedance spectroscopy from the nominal operating temperature range of 700–900°C down to temperatures as low as 350°C. At such low temperatures the dielectric polarization of the electrolyte is shifted into the accessible frequency range, providing access to additional processes which are deconvoluted and quantified. It is discussed to which extent the additional layers like gadolinia doped ceria diffusion barrier and electrode layers influence the electrolyte processes as grain and grain boundary.

Corrosion Inhibition in CO2-Saturated Brine by Nd3+ Ions.

This study reports the use of an inorganic corrosion inhibitor to mitigate dissolved CO2-induced corrosion. Using electrochemical techniques (polarization curves, open circuit potential, polarization resistance, and electrochemical impedance), the effect of adding Nd3+ ions on the corrosion resistance of X52 steel immersed in CO2-saturated brine at 20 °C and 60 °C was evaluated. The polarization curves showed that the Icorr values tend to decrease with increasing Nd3+ ion concentration, up to the optimal inhibition concentration, and that the corrosion potential increases at nobler values. Open circuit potential measurements showed a large increase in potential values immediately after the addition of the Nd3+ ions. Similarly, polarization resistance measurements showed similar trends. It was observed that regardless of temperature, Nd3+ ions can reduce the corrosion rate by more than 97% at doses as low as 0.001 M. Electrochemical impedance measurements confirmed the formation of a protective layer on the steel surface, which caused an increase in the magnitude of the impedance module and phase angle, which indicates an increase in the resistance to charge transfer and capacitive properties of the metallic surface. The characterization of the metallic surface showed that the protective layer was formed by Nd carbonates, whose formation was due to a CO2 capture process.

Measurements on macrocells made of segmented reinforcement in concrete showing environmental impacts on corrosion of steel in concrete

AbstractCorrosion of steel in concrete can be characterized by measuring the galvanic current density when a macrocell is established. On nonpolarized steel, however, other electrochemical techniques like linear polarization resistance measurements may be used to characterize the electrochemical state of steel in concrete. On existing structures with their large dimensions and local differences in exposure conditions, local differences in the electrochemical state of the embedded reinforcement are established, leading to potential differences along the reinforcement and galvanic currents flowing. When it is possible to isolate anodic areas from the rest of the reinforcement, both galvanic current measurements, determination of polarization resistance on the separated anodic areas and the driving force between the anodic segments and the reinforcement are possible to obtain. In this work, this procedure is discussed and verified on a field structure on anodic areas caused by cracks in the concrete overlay and the results thereof are presented.

Corrosion behavior and immobilization of pure aluminum and Al−Mg alloy LLRW in magnesium potassium phosphate cements

Magnesium potassium phosphate cement (MKPC) is a candidate material to replace ordinary Portland cement (OPC) for the encapsulation of metallic low-level radioactive waste (LLRW) and improve the corrosion behavior of encapsulated reactive metals such as aluminum. The objectives of this research were to study the corrosion behavior of pure Al (A1050) and Al−Mg alloy (AA5754) embedded in MKPC and OPC mortars, to assess the effect of curing conditions on hardening properties and on the reactivity of Al and Al−Mg alloy. Results were obtained with measurements of compressive strength, X-ray diffraction and polarization resistance and the proposed interpretation was based on Faraday´s law. In the first 15 days of interaction in water immersion the corrosion rate and the volume of hydrogen evolved were seen to be at least one order of magnitude lower for AA5754 in MKPC than in OPC mortar, yielding average corrosion current density values of 1.85 and 109.0 × 10−6 A/cm2, and hydrogen volumes of 0.33 L/m2 and 17.8 L/m2 for AA5754/MKPC and AA5754/OPC, respectively. The pore pH was close to neutral and the hardening properties were highly dependent on the curing conditions.

Electrochemical Studies of Magnesium Coated with Modified Chitosan and Electrosprayed as an Anticorrosive Protection Method in Bone Repair

Magnesium (Mg) is essential for the metabolic reactions of the human body and is known for its biocompatibility, its mechanical and physical properties are similar to human bone, which is why it is considered to have high potential in biomedical applications such as temporary and resorbable implants. Through surface modifications, the high tendency to corrosion of Mg could be controlled, such as biodegradable membranes that prevent the passage of chloride ions present in the human organism. To prepare the membrane, solutions of chitosan modified with gelatin and/or glutaraldehyde are used and by means of the electrospray method applied to protect the Mg. To simulate body fluid conditions a Kokubo saline solution (BFK) was prepared. The study focuses on evaluating the corrosion rate of Mg with a coating made of a chitosan electrosprayed membrane, applying electrochemical measurements of electrochemical impedance spectroscopy and linear polarization resistance. The key additive to improve the behavior of the membranes was observed with the use of gelatin, where the membrane with the best results lowing corrosion rates is the Mg CH+GE+GL system, which it was observed with very good physical integrity in the images of morphological analyzes of the surface after 30 days of exposure.

The San Carlo Colossus: An Insight into the Mild Galvanic Coupling between Wrought Iron and Copper.

The San Carlo Colossus, known as San Carlone, is a monument constituted by an internal stone pillar support to which a wrought iron structure is attached. Embossed copper sheets are fixed to the iron structure to give the final shape to the monument. After more than 300 years of outdoor exposure, this statue represents an opportunity for an in-depth investigation of long-term galvanic coupling between wrought iron and copper. Most iron elements of the San Carlone appeared in good conservation conditions with scarce evidence of galvanic corrosion. In some cases, the same iron bars presented some portions in good conservation conditions and other nearby portions with active corrosion. The aim of the present study was to investigate the possible factors correlated with such mild galvanic corrosion of wrought iron elements despite the widespread direct contact with copper for more than 300 years. Optical and electronic microscopy and compositional analyses were carried out on representative samples. Furthermore, polarisation resistance measurements were performed both on-site and in a laboratory. The results revealed that the iron bulk composition showed a ferritic microstructure with coarse grains. On the other hand, the surface corrosion products were mainly composed of goethite and lepidocrocite. Electrochemical analyses showed good corrosion resistance of both the bulk and surface of the wrought iron, and galvanic corrosion is not occurring probably due to the iron's relatively noble corrosion potential. The few areas where iron corrosion was observed are apparently related to environmental factors, such as the presence of thick deposits and to the presence of hygroscopic deposits that create localized microclimatic conditions on the surface of the monument.

An Electrochemical Study of the Corrosion Behaviour of T91 Steel in Molten Nitrates

A study of the corrosion behaviour of T91 steel in molten 60 wt% NaNO3-40%KNO3 has been carried out at 300, 400 and 500 °C during 1000 h. Employed techniques included potentiodynamic polarization tests, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements. Experiments were complemented by detailed scanning electronic measurements and X-ray diffraction studies. Polarization curves revealed the existence of a passive layer formed onto the steel, composed mainly of Cr2O3, FeCr2O4, NaCrO4 and K2Fe2O4. Corrosion current density values increased, whereas the polarization resistance value decreased more than one order of magnitude as the testing temperature increased. EIS tests indicated a charge transfer controlled corrosion process, regardless of the testing temperature, and that the double electrochemical layer resistance decreased with the temperature.

Steel Pipe Internal Corrosion Protection Using Magnesium Anode: Impact of Protective Potential and Phase Layer Formation on Corrosion Rate

The influence of magnesium anode dissolution in pipe filled with potable water on the steel corrosion rate was investigated. Steel corrosion rate was measured using the weight loss technique, and linear polarization resistance measurements were used to estimate the formation kinetics and protective abilities of the phase layer on the metal surface. The cathodic current distribution along steel pipe was measured using a microammeter and compared with the computer model. The results clearly demonstrate that the reduction of metal corrosion rate is at least 2.8 times in the region where cathodic protection distributes inside the pipe. However, for the remaining part of the metal pipe, the reduction of corrosion rate of 1.5 times was obtained due to the formation of the phase layer on the metal surface that leads to the reduction of oxygen supply. The results obtained in the study can be further applied for designing and maintenance of water supply systems.

Protective Characteristics of TiO2 Sol-Gel Layer Deposited on Zn-Ni or Zn-Co Substrates

This study aimed to present the differences in the corrosion properties and protective ability of two bi-layer systems obtained on low-carbon steel in a model corrosive medium of 5% NaCl solution. These newly developed systems consist of Zn-Co (3 wt.%) or Zn-Ni (10 wt.%) alloy coatings as under-layers and a very thin TiO2 sol-gel film as a top-layer. Scanning electron microscopy (SEM) is used for characterization of the surface morphology of the samples indicating that some quantitative differences appear as a result of the different composition of both zinc alloys. Surface topography is investigated by means of atomic force microscopy (AFM), and the hydrophobic properties are studied by contact angle (CA) measurements. These investigations demonstrate that both sample types possess grain nanometric surface morphology and that the contact angle decreases very slightly. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used for characterization of the chemical composition and electronic structure of the samples. The roughness Rq of the Zn-Ni/TiO2 is 49.5 nm, while for Zn-Co/TiO2, the Rq value is 53.4 nm. The water contact angels are 93.2 and 95.5 for the Zn-Ni/TiO2 and Zn-Co/TiO2 systems, respectively. These investigations also show that the co-deposition of Zn and Ni forms a coating consisting entirely of Ni2Zn11, while the other alloy contains Zn, Co and the intermetallic compound CoZn13. The corrosion resistance and protective ability are estimated by potentiodynamic polarization (PDP) curves, as well as polarization resistance (Rp) measurements for a prolonged test period (35 days). The results obtained are compared with the corrosion characteristics of ordinary zinc coating with an equal thickness. The experimental data presents the positive influence of the newly developed systems on the enhanced protective properties of low-carbon steel in a test environment causing a localized corrosion—lower corrosion current density of about one magnitude of order (~10−6 A.cm−2 for both systems and ~10−5 A.cm−2 for Zn) and an enhanced protective ability after 35 days (~10,000–17,000 ohms for the systems and ~900 ohms for Zn).

Quebracho tannin as corrosion inhibitor in neutral media and novel rust conversion agent for enhanced corrosion protection

In the present work, the anticorrosive properties of quebracho tannins extract (QE) were tested in neutral solution to protect mild steel and a new rust conversion agent based on QE was developed. QE remarkably rich of total phenolic compounds (TPC) (2630.1 ± 11.43 mg gallic acid equivalent (GAE)/g) and flavonoids (81.36±1.20 mg quercetin equivalent (QUE)/g) was revealed. QE have shown good antioxidant activity (75% and 68% DPPH and ABTS radical scavenging activities at 500 mg/L of QE, respectively). The inhibition corrosion process of steel in 3.5% NaCl solution by QE have been studied using potentiodynamic polarization and polarization resistance measurements. The steel surface is acquired by scanning electron microscopy (SEM). Density functional theory (DFT) was used to give further insight into the adsorption and inhibition mechanism of QE on the steel surface. A tannin primer was prepared and coated panels were tested in salt spray chamber.

Inhibition of X52 Corrosion in CO2-Saturated Brine by a Dialkyl-Diamide from Coffee Bagasse Oil.

This work reports the performance of a green corrosion inhibitor with double hydrocarbon chain. The evaluated inhibitor was a dialkyl-diamide from coffee bagasse oil and its electrochemical behavior was evaluated on an API-X52 steel in CO2-saturated brine at 60 °C. The electrochemical behavior was determined by measurements of open circuit potential, polarization resistance, and electrochemical impedance spectroscopy. In addition, the thermodynamic parameters of the corrosion process were obtained in the temperature range from 40 °C to 80 °C. Electrochemical studies showed that the inhibitor is capable of suppressing metal dissolution by up to 99% at 25 ppm. On the other hand, the thermodynamic parameters indicate that when adding the inhibitor, there is a strong increase in both Ea and ΔH° values, and that as time increases, they decrease until reaching similar values to those observed in the absence of the inhibitor. Furthermore, ΔS° values tend to become more negative with immersion time because of the formation of a stable film on the metal surface.