Tafel Extrapolation Method Research Articles

Characterization of Ti–6Al–(4V–7Nb–4Mo) Biomedical Alloys Produced by Powder Metallurgy Method

Pure titanium and titanium-based alloys are the most widely used metallic biomaterials in biomedical applications. At that, the Ti–6Al–4V alloy is considered as the most commonly exploited alloy among all alloys that contain titanium. However, it is known that the vanadium metal that constitute this alloy has a potential toxic effect. In this study, the powder metallurgy (PM) method was used for the production of pure-Ti, as well as Ti–6Al–4V, Ti–6Al–7Nb, and Ti–6Al–4Mo alloys. Niobium and molybdenum elements, one of the alloying metals, have been proposed as a substitution of vanadium due to its possible toxic effects. Produced samples were characterized by SEM, EDX, XRD, as well as microhardness, density, and Tafel extrapolation method. The analysis results showed that microstructure of pure titanium and titanium-based alloys differ. Besides, the XRD analysis showed that the phases of doped metals (Nb, V, and Mo) were found as Al0.23Nb0.07Ti0.70, Ti0.80V0.20, and AlMoTi3. Microhardness and Tafel extrapolation values were quite remarkable by comparing them to each other. The main important result of the research was obtained pure titanium and titanium alloys with homogeneous microstructure produced by the powder metallurgy method.

A Study on the Effects of Different Heat‐Treatment Parameters on Microstructure–Mechanical Properties and Corrosion Behavior of Maraging Steel Produced by Direct Metal Laser Sintering

Herein, direct aging (aged‐490 °C/6 h) and solution heat treatment and subsequent aging (SHT‐940 °C/2 h + 490 °C/6 h) heat treatments are applied to maraging steel (MS1) produced by direct metal laser sintering (DMLS) method. The effects of these heat treatments on microstructure, phase transformations, mechanical properties, and corrosion properties in MS1 are given in comparison with the as‐built state. Optical microscope (OM) and scanning electron microscope (SEM) is used for microstructure measurements, electron dispersion spectroscopy (EDX), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD) methods are used to determine the phase transformations. Potentiodynamic polarization tests are applied to determine the corrosion resistance of the material, and stereo OM and the Tafel extrapolation method is used to examine the corrosion results. The hardness test is carried out with a Rockwell C method to determine the mechanical character of the material. According to the results obtained, it is determined that the applied heat treatments affect the hardness and corrosion resistance of the material by changing the microstructure and phase transformations of MS1 material produced with DMLS.

Development of nanocrystalline multilayer Ni–Fe alloy coatings: characterization and its corrosion behaviour at elevated temperature

The present work deals with the galvanostatic fabrication of Ni–Fe nanostructured composition-modulated multilayer alloy (CMMA) coatings on steel panel from the newly optimized acid-sulphate bath solution. The recurring cathode current density combination (RCCC) and the number of layers have been optimized for enhanced performance of the coatings against corrosion. Corrosion behaviour of the nanostructured multilayered coatings was evaluated by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) methods in 3.5% NaCl solution. Under optimal conditions, the CMMA coatings developed were more corrosion-resistant than the monolithic alloy coatings obtained from the same bath. Least corrosion rate (CR) was witnessed at 300 layers, above which saturation of corrosion resistance at a high temperature was found, which is attributed to a shorter relaxation time for redistribution of metal ions during multilayer deposition. Hardness and roughness of the coatings were evaluated using Vickers hardness test and atomic force microscope, respectively. Phase structure of the coatings was discussed using X-ray diffraction technique. The cross-sectional view of the coatings was characterized by scanning electron microscope. CR analysis and the surface morphology of the optimized coatings exposed to high temperature revealed the better performance of CMMA coatings at the elevated temperatures compared to the monolithic coatings.

Access to nanocrystalline, uniform, and fine-grained Ni-P coating with improved anticorrosive action through the growth of ZnO nanostructures before the plating process

In this work, the mild steel surface was modified by the growth of ZnO nanoflakes through a feasible and scalable procedure. The modified surface was used for the coating by the electroless nickel (EN) plating, and the influence of this modification on the morphology, surface roughness, uniformity, the corrosion behavior of Ni-P coating, and also on the deposition rate of EN plating was studied. The SEM micrographs, especially backscatter images, disclosed that the matrix of Ni-P coating with the underneath of ZnO NSs possesses smaller grain size with more uniform distribution compared to the specimen without ZnO NSs. The AFM analysis affirmed the lower surface roughness of this sample. The results of the EIS measurements and the Tafel extrapolation method indicated that the corrosion resistance of this sample is approximately two times higher than that of the sample without zinc oxide (Rp ≈ 35,000 Ω cm2). The role of ZnO NSs in increasing the active nucleation density and the formation of uniform, compact, and fine-grained Ni-P deposit was discussed. Besides, the effects of ZnO NSs on generating scattering centers, restricting the electron transfer, strengthening the Ni-P matrix, and the consequent corrosion behavior, were investigated.

An Evaluation of Carbon Steel Corrosion in Nitrate Solution Using Electrochemical and Solution Analysis Methods

Nuclear power reactors offer a long term, cost efficient and sustainable method to produce electricity with very low greenhouse gas emissions. As nuclear reactors age and their lifetimes are extended, accurate assessment of the integrity and longevity of the reactor structural materials is increasingly important. Corrosion in the vicinity of a nuclear reactor core happens in the presence of high energy, ionizing radiation, which needs to be considered. In particular, the potential for accelerated (galvanic) corrosion attack on carbon steel (CS) adjacent to the dissimilar metal weld between CS (SA 36) and stainless steel (SS) (Type 304L) at the periphery of the annular gap must be addressed.The initial environment inside the gap of structural support for End Shield Cooling (ESC) System could be humid due to trapped water in its annular gap. The pH of the ESC System water is adjusted to around 10.4, but when it condenses onto the weld region the pH might change. The oxygen level, the humidity, and many other factors will change with time. In addition, ionizing radiation decomposes water into a range of redox active species ranging from highly oxidizing (e.g., •OH and H2O2) to highly reducing (e.g., •eaq -) whose concentrations evolve with time (1-4). Humid-air radiolysis produces nitric acid (HNO3), that can dissolve into the water (5). The radiation products will lower the pH of the water in the droplet.In this work, corrosion of CS is evaluated carefully, and the effect of all solution reactions on interfacial charge transfer reactions is considered.The effect of [NO3 -] and solution pH is studied by using potentiodynamic polarization experiments and corrosion potential measurements (Figure 1), along with solution analysis. The results of polarization measurements in the presence of 0.01 M and 0.1 M [NO3 -] (with initial pH 2.0) show that the oxidation reactions are implicitly influenced by the mass transfer of metal cations from the CS surface into the solution. Also, the comparison of the rate of corrosion measured using Tafel extrapolation method and those obtained from ICP measurements suggests that the Tafel extrapolation method enormously underestimate the corrosion rate (in this case by about 100 times for 8 h corrosion) and must be applied more carefully.In order to study the effect of pH, we have compared the electrochemical results in pH 2.0 and pH 6.0 obtained in different concentrations of nitrate. The results show that solution pH is a rate controlling factor and the metal oxidation is limited by the metal transfer even at potentials close to/at the corrosion potential, and this influence the rate of corrosion.The results of this work imply that solution reactions can alter the corrosion behavior of carbon steel and hence, its galvanic coupling with stainless steel.

Corrosion inhibitor behavior in typical car radiators

A minor breakdown of the cooling system will cause engine overheating. One of the factors causing the engine overheating is the crust on radiator of cooling system. Based on the problem, therefore, corrosion on the cooling system, especially radiator, should be controlled. There are some methods in controlling the corrosion; one of them is the inhibitor treatment. The research aims to know the corrosion mechanism, the corrosion type, and the kind of inhibitor that produces the lowest corrosion rate. The tool used to measure the chemical composition of the radiator is spectrometer, while microscope optic is used to know the radiator corrosion type. The corrosion rate testing is used three electrode cells according to tafel extrapolation method. The results of the test of the nitric acid inhibitor treatment with the addition of various methods showed that the most optimal result is on the addition of nitric acid inhibitor by 5%. It is proven by the decrease of corrosion rate from 0.002207 mmpy to 0.0171 mmpy.

Potential step voltammetry: An approach to corrosion rate measurement of reinforcements in concrete

This paper presents a Potentiostatic Step Voltammetry approach to corrosion rate measurement of reinforcements in concrete. We have termed this approach PSV-TE since it is based on the Tafel extrapolation method, but with the added advantage that long and slow potentiodynamic scans are no longer required to obtain the Tafel slopes. In this way, the irreversible polarization of rebars is prevented, so PSV-TE is considered to be a non-destructive method. The Tafel slopes are obtained by fitting the current-time response of the system to a theoretical model which we have outlined and validated previously. In this way, the concrete's electrical resistance and double layer capacity are also obtained. In this study, the optimal PSV-TE design has been established and validated on a range of reinforced concrete specimens. Results show minimal deviation between PSV-TE and reference methods. Therefore, PSV-TE is part of the corrosion monitoring system we have patented.

Unraveling the effects of surface preparation on the pitting corrosion resistance of austenitic stainless steel

The effects of surface preparation on the corrosion resistance of AISI 316L austenitic stainless steel were studied using the cyclic potentiodynamic polarization method. Grinding, mechanical polishing, and electropolishing were considered as the surface modifier methods. Regarding the surface roughness parameters, besides the conventional height parameter (Ra), the kurtosis (Rku) as the shape parameter was also considered to rationalize the pitting resistance for the first time. Based on the results of the Tafel extrapolation method, it was revealed that the uniform corrosion can be adequately correlated to Ra. However, the pitting resistance was found to mainly relate to the kurtosis, where by decreasing Rku (increased bluntness of topographic features), the pitting resistance enhanced. It was also found that a surface with Rku less than three (platykurtic) is resistant to pitting attack, where this surface can be obtained via electropolishing performed for an optimum time. The effect of electropolishing on the chromium content at the surface and its relation to the corrosion properties were also discussed.

Electrochemical Corrosion Resistance of Ni and Co Bonded Near-Nano and Nanostructured Cemented Carbides

The advantages of nanostructured cemented carbides are a uniform, homogenous microstructure and superior, high uniform mechanical properties, which makes them the best choice for wear-resistant applications. Wear-resistant applications in the chemical and petroleum industry, besides mechanical properties, require corrosion resistance of the parts. Co as a binder is not an optimal solution due to selective dissolution in an acidic environment. Thus, the development of cemented carbides with alternative binders to increase the corrosion resistance but still retaining mechanical properties is of common interest. Starting mixtures with WC powder, grain growth inhibitors GGIs; VC and Cr3C2, and an identical binder amount of 11-wt.% were prepared. GGIs were added to retain the size of the starting WC powder in the sintered samples. The parameters of the powder metallurgy process were adapted, and samples have been successfully consolidated. A very fine homogeneous microstructure with relatively uniform grain-size distribution and without microstructural defects in the form of carbide agglomerates and abnormal grain growth was achieved for both Ni-bonded and Co-bonded samples. Achieved mechanical properties, Vickers hardness, and Palmqvist toughness, of Ni-bonded near-nanostructured cemented carbides are slightly lower but still comparable to Co-bonded nanostructured cemented carbides. Two samples of each grade were researched by different electrochemical direct current corrosion techniques. The open circuit potential Ecorr, the linear polarisation resistance (LPR), the Tafel extrapolation method, and the electrochemical impedance spectroscopy (EIS) at room temperature in the solution of 3.5% NaCl. From the carried research, it was found that chemical composition of the binder significantly influenced the electrochemical corrosion resistance. Better corrosion resistance was observed for Ni-bonded samples compared to Co-bonded samples. The corrosion rate of Ni-bonded cemented carbides is approximately four times lower compared to Co-bonded cemented carbides.

An Investigation on Anti-Corrosion Properties of Electroplated Copper-Graphene Nano-Composite Films

In this report, graphene sheets used as reinforcements for improvement of anti-corrosion properties have been synthesized by electrochemical intercalation and exfoliation process. The (001) and (002) plane of graphene sheets at a 2θ angle of 13.2 and 26.13 confirmed by X-ray diffraction pattern. High-resolution TEM confirms 8-12 layers of graphene present in the final products. The as-received graphene sheets have been used as reinforcement with copper matrix to synthesize Cu-Gr nanocomposite by electrodeposition method. The results and investigations of Cu-Gr composite thin films deposited from the bath containing 0.1g/L and 0.5g/L graphene concentrations with acidic copper sulfate solution have been compared. The surface morphology and roughness of composites were studied by SEM, AFM and surface profiler. The presence of graphene in Cu-Gr nanocomposite confirmed by EDS analysis. It was observed that the reinforcement particle has increased the mechanical properties of Cu-Gr composite (by 30%) with the addition to the copper matrix. The corrosion resistance of sample was studied by Tafel extrapolation method in standard borate buffer solution. For nanocomposites of 0.5g/L graphene, the values of Tafel constants are, βa=177.37 mv, βc=138.51 mv, Icorr = 9.3165×10-7Amp/cm2, Ecorr = -0.051 volts and corrosion rate 0.01028 mm/a as comparison to the corrosion rate of pure electroplated copper of a value of 0.029 mm/a. The corrosion rate of 0.5g/L Cu-Gr composite was found to be decreased by 2.7 times as compared to pure copper thin films. The structure of the films before and after corrosion was also analyzed to co-relate the electrochemical and structural relationship.

Cyanide-free silver immersion deposition involving 3-mercapto-1-propanesulfonic acid for copper finishing

In this work, in the place of cyanide, a novel alternative of silver ligand, 3-mercapto-1-propanesulfonic acid (MPS), is introduced for environmentally friendly copper finishing by a galvanic replacement reaction. The bright yellow and transparent MPS-Ag solution exhibits high chemical and thermal stability. Cyclic Voltammetry (CV) plots prove the coordination ability of MPS to Ag+ is much stronger than that of ammonia in alkaline solution. By applying different temperatures and solution compositions, various silver deposits were prepared by immersion of silver on copper surface in solutions with MPS. The obtained samples were subjected to morphological and chemical characterizations to analyze the composition of corresponding silver deposits. Experimental results show that, the size of the deposited silver particles is tunable by controlling the concentration of Cl− and temperature. Additionally, corrosion tests based on Tafel extrapolation method validate the favorable performance of the corrosion resistance and low coating porosity of the silver deposits. It was observed that, in the absence of Cu+, copper alone cannot reduce the Ag+ in MPS solutions, indicating that Cu+ is the critical component in the reactions involving MPS-assisted replacement. Combined with the experimental output, quantum chemical calculations based on Density Functional Theory (DFT) were employed to explain the mechanism of this particular chemical reaction.

Determination of corrosion protection current density requirement of zinc sacrificial anode for corrosion protection of AA5083-H321 in seawater

In this study, the current density requirements of zinc sacrificial anode for corrosion protection of AA5083-H321 aluminum hull for the ship was determined through various electrochemical tests. Surface observation and chemical composition analysis were performed after the galvanostatic test for various current density requirements determined by the cathodic polarization experiment. As a result, the most appropriate current density requirement range was determined as 3.7 × 10−6–5.8 × 10−6 A/cm2. Excessive current density over 7.6 × 10−6 A/cm2 caused local surface damage due to the effect of Mg-rich and Fe-rich intermetallic phases. In addition, the self-consumption of zinc sacrificial anode was determined through Tafel's extrapolation method.

Estimating Energy Consumption and Cost for the Electrocoagulation of Arsenic-laden Water (ECAR) Using Iron Electrodes

In some areas in Pampanga, arsenic concentration from handpumps reaches up to 300 μg/L, 10 times higher than the safe limit for drinking water. An efficient way of reducing elevated arsenic concentration is through electrocoagulation (EC) process with the use of iron electrodes. However due to several factors, the efficiency of the technique is decreased. This study focuses on determining the energy consumption and cost through time. The cost per cycle was estimated through the power consumption and projecting its growth with time. One 600 L cycle costs around $0.60 to $1.10 which is approximately $0.001 to $0.002 per liter of water. This value increases through each cycle until half of the electrode is consumed (500 cycles) and is to be replaced. The current processing time was set at 30 mins, charge dosage of 150 C/L, applied current of 16.67 mA, and an electrode area of 6.6 cm2. One factor examined which may have caused the increase is the formation of passivation layer on the electrode surface. It was described using linear sweep voltammetry (LSV) and Tafel extrapolation method. The resistance due to charge transfer was determined to be increasing per cycle.

Theoretical and Experimental Study of the Acid Corrosion Inhibition of Copper by Aspirin (Acetylsalicylic Acid)

The inhibition efficiency of aspirin (acetylsalicylic acid-ASA) against copper corrosion was investigated in 0.5 M HCl solution at room temperature by using electrochemical techniques. Furthermore some quantum chemical calculations were done to explain the inhibition mechanism of ASA. It was found that ASA has a promising inhibitory action against corrosion of copper in the medium investigated. The polarization curves of ASA were obtained from electrochemical measurements. According to potentiodynamic results, ASA inhibits the corrosion process of the copper cathodically and its ability as a corrosion inhibitor is enhanced as its concentration is increased. The Tafel extrapolation method was used to calculate some corrosion parameters, such as corrosion potential (Ecorr), corrosion current (Icorr), cathodic Tafel slope (βc) and anodic Tafel slope (βa). Additionally, Langmuir adsorption isotherm was used to explain the adsorption behavior of ASA on copper surface. The adsorption equilibrium constant (Kads) and the standard free energy of adsorption ($$\Delta G_{{{\text{ads}}}}^{^\circ }$$) were calculated from Langmuir adsorption isotherm. It can be concluded that the adsorption of ASA on the copper surface contains mostly physisorption but also chemisorption thereby it is so called a mixed. The quantum chemical calculations have been performed on ASA for neutral and protonated forms by using density functional theory (DFT) in gas and aqeuous phases to explain the behavior of ASA as a corrosion inhibitor. These calculated quantum chemical parameters were compared to each other and the relationship between calculated parameters and corrosion inhibition mechanism of ASA is analysed.

Deposition of TiN and TiAlVN thin films by DC magnetron sputtering

Purpose TiN and TiAlVN films have been prepared by DC magnetron sputtering technique at room temperature. TiN target has been used to deposit TiN thin film under pure argon (100 percent Ar) gas. Additionally, Ti6Al4V alloy target has been used to deposit TiAlVN under nitrogen and argon gas (50 percent Ar and 50 percent N2). In this paper, two substrate types have been used: stainless steel 304 and Si(100). This analysis has confirmed that the nitride films, (TiN/Si) and TiAlVN in both cases, have been produced. Energy Depressive X-ray Spectroscopy (EDX) measurement confirmed that the TiN/Si was stoichiometry, where the N/Ti ratio was about 1 with low oxygen contamination. The results obtained have indicated that the TiAlVN has more resistance to corrosion than TiN film in 3.5 percent NaCl at 25°C (seawater). Both films, TiAlVN/SS304 and TiN/SS304, have shown improved corrosion resistance compared with virgin 304 substrate. Microhardness was carried out using Vickers method; the microhardness values for TiN/SS304 and TiAlVN/SS304 were approximately 7.5 GPa and 25.3 GPa, respectively. The paper aims to discuss these issues. Design/methodology/approach The films were prepared by a DC magnetron sputtering system starting from high pure (99.99 percent) Ti6Al4V target (Al 6wt%, V 4wt% and balance Ti) in plasma discharge argon/nitrogen (50 percent Ar and 50 percent N2) for deposition of TiAlVN film. Pure TiN target (99.99 percent) was used for preparation of TiN film in pure argon plasma. The diameter of target was 50 mm and the power applied for preparation of the two films was 100 W. A cylindrical high-vacuum chamber (Figure 2) made of stainless steel 316, with height 363 mm diameter, was fabricated locally. Scanning electron microscope images have been used to discover the films morphology. The composition of the films has been determined by EDX technique for films deposited on Si substrate. The electrochemical corrosion test was carried out using conventional three-electrode cell of 300 ml capacity by using Voltalab PGZ 301 system (France) using Tafel extrapolation method and electrochemical impedance spectroscopy techniques. Findings TiN and TiAlVN films have been prepared by DC magnetron sputtering technique without heating of the substrates holder. The effects of the composition of nitride films on mechanical and corrosion properties were investigated. The composition of the films has been determined by EDX technique. The effect of using titanium alloy (Ti with Al and V) on the composition and crystalline quality has been investigated. The microhardness is strongly dependent on the addition of the Al and V elements, and it consequently improves mechanical proprieties. The microhardness values for TiN/SS304 were approximately 7.5 GPa and 25.3 GPa for TiAlVN/SS304. They indicate that prepared films prevent the aggressive action of corrosion media. Originality/value TiN and TiAlVN films have been prepared by DC magnetron sputtering method at room temperature. Titanium nitride film, especially TiAlVN, is an effective method to improve the corrosion resistance of SS304. TiAlVN film has exhibited enhanced corrosion resistance and higher microhardness. Independent time-of-flight elastic recoil detection analysis has been used to determine the composition of the film.

Estimation of exchange current density for hydrogen evolution reaction of copper electrode by using the differentiating polarization method

Wide application of the Tafel extrapolation method (TEM) for the estimation value of the exchange current density (i0) on the hydrogen evolution reaction (HER) is still hindered because of some issues. For example, a possibility of improper reading of the tafel slope and the physical resistant such as an oxide film on electrode and solution resistance which requires more consideration in the calculation. The differential polarization method (DPM) was introduced as a reliable method to estimate the value of the i0. In this paper, HER of a copper electrode in 0.5 mol dm−3 H2SO4 solution was investigated and compared using both methods. The DPM shows that the undesirable physical factor of copper in the measurement could be removed rationally and is acceptable on the calculation of i0. Moreover, the tafel slope region could be read accurately.

Effect of selective-precipitations process on the corrosion resistance and hardness of dual-phase high-carbon steel

It is commonly known that precipitation of secondary phase in non-ferrous alloys will affect the mechanical properties of them. But due to the nature of dual-phase low-alloy high-carbon steel and its high potential of precipitation of cementite, there is limited study on tailoring the mechanical and corrosion properties of this grade of steel by controlling the precipitation of different phases. Predicting and controlling precipitation behaviour on this grade of steel is of great importance towards producing more advanced applications using this low-cost alloy. In this study the new concept of selective-precipitation process for controlling the mechanical and corrosion behaviour of dual-phase low-alloy high-carbon steel has been introduced. We have investigated the precipitation of different phases using in-situ observation ultra-high temperature confocal scanning laser microscopy, image analyser – ImageJ, scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and electron probe microanalysis (EPMA). Volume fraction of each phase including retained austenite, martensite and precipitated phases was determined by X-ray diffraction (XRD), electrochemical corrosion test by Tafel extrapolation method and hardness performance by nanoindentation hardness measurement. The experimental results demonstrated that, by controlling the precipitations inside the matrix and at grain boundaries through heat treatment, we can increase the hardness of steel from 7.81 GPa to 11.4 GPa. Also, corrosion resistance of steel at different condition has been investigated. This new approach will open new possibility of using this low-cost steel for high performance applications.

Corrosion grade classification: a machine learning approach

ABSTRACT Corrosion tests allow to have information to indicate the state of materials in certain applications when environmental specifications are not met. It allows developing new material coatings to improve resistance to degradation. The area of materials inspection has relevance in construction, manufacture and medicine. In this work, we present an image corrosion classification method based on visual features and SVM (support vector machine). The feature extraction procedure includes SIFT (scale invariant transform features) and BOW (bag of words) approaches. The performance of classifiers is compared over the kernel function and the involved parameters. The experimental methodology known as the Tafel extrapolation method performed on each corrosion sample to find the corrosion rate and the corrosion current and voltage. A comparison between the Tafel test and the developed vision-based approach allows to see the high potential of the developed process to differentiate between pitting and general corrosion.

Experimental and theoretical investigations for some spiropyrazoles derivatives as corrosion inhibitors for copper in 2 M HNO3 solutions

Rates of corrosion for copper were monitored in aerated stagnant 2 M HNO3 solutions at different temperatures (25-55 °C) using Tafel extrapolation method, electrochemical impedance spectroscopy technique, non-destructive electrochemical frequency modulation (EFM) technique and weight-loss method, accompanied by EDX examinations, molecular docking, molecular dynamics, and quantum chemical calculations. Some spiropyrazoles derivatives were introduced as corrosion-safe inhibitors. Compound (1) has the best inhibition activity (89.9% at 11 × 10−6M). Tafel plots indicated that these compounds acted mainly as mixed-type inhibitors. The inhibition process was ascribed to the formation of an adsorbed film on the copper surface that protects the metal against corrosive agents. EDX examinations of the electrode surface confirmed the existence of such adsorbed film. The inhibition efficiency increased by increasing the concentration of spiropyrazoles compounds, while it decreased by increasing the temperature, this expresses on the physical adsorption. Activation energy has been calculated in the existence and nonexistence of a number of concentrations from spiropyrazoles derivatives by measuring the corrosion rate obtained from the weight loss method at different temperatures. It was found that the activation energy in the presence of spiropyrazoles derivatives is higher than that in 2 M HNO3 solution alone. The adsorptive behavior of spiropyrazoles compounds followed Freundlich -type isotherm.

Electrochemical and theoretical assessment of the effect of two biocides on the corrosion of petroleum steel in sulfur‐polluted Black Sea water

AbstractAlthough the inhibitory effects of different biocides continue to gain ever‐increasing importance, the corrosion inhibition of petroleum steel in the Black Sea water by such compounds remains largely uncharacterized. Thus, to study the effect of sulfate‐reducing bacteria, corrosion parameters in oxygen‐free medium contaminated with sulfur have been determined. The variation of corrosion rates with the addition of two biocides, glutaraldehyde (GA) and ammonium chloride (AC), has been determined by using Tafel extrapolation and linear polarization methods in sulfur‐polluted seawater, both with and without biocides. Overall, this experimental work, also corroborated by theoretical data, reveals that some concentrations of GA and AC act as effective biocides in sulfur‐polluted medium.