Tafel Extrapolation Research Articles

A Study on the Self-Discharge Behavior of Zinc-Air Batteries with CuO Additives

Zn-air batteries have promise as the next generation of batteries. However, their self-discharge behavior due to the hydrogen evolution reaction (HER) and corrosion of the Zn anode reduce their electrochemical performance. Copper (II) oxide (CuO) effectively suppresses the corrosion and HER. In addition, different electrochemical behavior can be obtained with different shape of nano CuO. To improve the performance of Zn-air batteries, in this study we synthesized nano CuO by the hydrothermal synthesis method with different volumes of NaOH solutions. Materials were characterized by XRD, FE-SEM, and EDX analysis. The sphere-like nano CuO (S-CuO) showed a specific discharge capacity of 428.8 mAh/g and 359.42 mAh/g after 1 h and 12 h storage, respectively. It also showed a capacity retention rate of 83.8%. In contrast, the other nano CuO additives showed a lower performance than pure Zn. The corrosion behavior of nano CuO additives was analyzed through Tafel extrapolation. S-CuO showed an Icorr of 0.053 A/cm2, the lowest value among the compared nano CuO materials. The results of our comparative study suggest that the sphere-like nano CuO additive is the most effective for suppressing the self-discharge of Zn-air batteries.

Characterization & electrochemical behavior of DC & PC methods of electrodeposited Ni-TiO2-CNTs nanocomposite coatings

Pure Nickel coatings and Nickel-Titanium dioxide-Carbon Nanotubes (Ni-TiO2-CNTs) nanocomposite coatings have been developed on mild steel substrate by Direct Coating (DC) and Pulse Coating (PC) methods of electrodeposition. Plating parameters are optimized. The structure and surface morphology of coatings were carried out using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Analysis of x-ray (EDAX). The corrosion resistance was investigated using Tafel extrapolation and AC impedance techniques. The preferred growth direction for nickel changed from (200) to (111) during inclusion on nanoparticles. A bath composition of 0.75 g l−1 of nanoparticles was optimum for getting coatings with high corrosion resistance and micro hardness.

Effects of different pH of 3.5% NaCl solution on steel under zero charge corrosion protection technique

The study is carried out to understand the new corrosion protection technique, non-polarization concept, using current/voltage pulses to achieve a potential of zero charges (Epzc) of the metal-solution interface. As a result, a cost-saving and ecological method has been proposed as a new anti-corrosion method. In the methodology, U-bend samples are immersed in a 3.5% NaCl solution with different pH values. The readings prove the occurrence of electrochemical reaction, absence of charges, and the effect of Epzc. An examination on the ZCCP on low-carbon steel in 3.5% NaCl solution was analyze for 120 hours days. This study is carried out to understand the concept of corrosion behaviour and a new corrosion protection technique which applies non-polarization concept. A U-bend mild steel is used to corrosion effect in various pH values under zero charge protection. Samples were then immersed in 3.5% NaCl solution with different pH values. Electrochemical behaviour of steel sample in 3.5% NaCl solution was analysed by means of Tafel extrapolation. It was found that Ecorr and icorr recorded dissimilar readings at different pH values. As Ecorr rises, icorr drops from pH 6 to pH 9, hence corrosion rate also decreases from pH 6 to pH 9. Zero charge corrosion protection (ZCCP) technique is used to study the efficiency of corrosion protection method in different pH values. Readings of alternating current (IAC) and direct voltage (VDC) are recorded throughout the ZCCP experiment. These readings prove the occurrence of electrochemical reaction, absence of charges and the effect of Epzc.

Effect of sulfur content in the crude oil to the corrosion behavior of internal surface of API 5L X65 petroleum pipeline steel

This work discussed the corrosion behavior of the internal surface of pipeline steel caused by the composition of petroleum products, particularly crude oil. Internal and external pipeline corrosion is the notable cause of pipeline failure in Malaysia’s oil and gas industry. However, internal corrosion is preferred to be concerned in this work because it involved one of the major corrosive media in the crude oil, such as sulfur content. This project aim is to find the sulfur concentration in the crude oil using Fourier transform infrared spectroscopy and atomic absorption spectroscopy. The corrosion rate, corrosion current and corrosion potential of the API 5L X65 grade carbon steel pipeline in different simulated H2SO4 solution concentrations were carried out using the Tafel extrapolation technique. The corrosion properties of the samples were morphologically measured by means of optical microscope, scanning electron microscope and energy dispersive X-ray analyses. The results showed that the corrosion rate of the pipeline steel significantly increased with the increasing H2SO4 concentrations. The corrosion products formed on the pipeline steel surfaces were mainly composed of iron sulfate, iron sulfide and iron oxide. These findings are crucial to understanding the corrosion behavior caused by the crude oil and should be further investigate with the other possible influence factors such as temperature and petroleum’s flowing velocity.

Electrochemical corrosion response of ZrN coated Nickel-Titanium alloy in 0.9% NaCl solution

Abstract: The biomedical application as metallic body implants of Nickel-Titanium shape memory alloys are of high interest due to its unique property of pseudo elasticity. However, high content of nickel and its potential to release from the surface due to corrosion raises safety concerns about its allergic reactions, toxicity and carcinogenicity. Hence, it is necessary to produce proper passivity to prevent surface layer degradation. In this study, ZrN coating on Nickel-Titanium shape memory alloys was obtained by vacuum cathodic arc physical vapor deposition technique to improve electrochemical corrosion resistance. The electrochemical corrosion response was studied in 0.9% NaCl solution at 370C using Tafel extrapolation method. Surface morphology was studied using SEM/EDAX and XRD. ZrN coating increases corrosion stability and micro hardness. Keywords: Shape memory alloy; pseudoelasticity; vacuum cathodic arc PVD; electrochemical corrosion; micro hardness.

Electrochemical Behavior of a Stainless Steel Superficially Modified with Nitrogen by Three-dimensional Ion Implantation

Martensitic-grade stainless steels are widely used in diverse industrial and surgical applications, despite their natural tendency to suffer local and uniform corrosion when continuously exposed to aggressive operation conditions. In order to enhance their surface properties, this paper characterized the performance, in saline solutions, of AISI 420 stainless steel, which was surface-modified by three-dimensional ion implantation using electrochemical techniques. The surface of the samples was implanted with ionized nitrogen particles with an energy of 10 keV, varying the implantation time between 30 and 90 minutes. After the surface treatment, the samples were exposed to a NaCl 3% (w/w) aqueous solution for 21 days. Tafel extrapolation, linear polarization resistance, and electrochemical impedance spectroscopy tests were performed, with the purpose of quantifying the effect of the ion implantation technique against electrochemical corrosion. To establish a comparison, the same tests were also performed on non-treated samples. The results indicated an increase in the corrosion potential, polarization resistance, and a decrease in the current density of implanted samples, thus demonstrating that, by delaying corrosive activity, traditional ion implantation offers better protection against electrochemical corrosion in AISI 420 stainless steel samples implanted with nitrogen.

Improvement of corrosion resistance of galvanization/nickel/chrome plating low carbon steels in H2SO4 under dynamic condition

In this work, the corrosion resistance of metallic coating (ISO 1416) deposited on AISI 1080 low carbon steel has been investigated under static and dynamic conditions (flow rate 30 rpm). The coated steels have been immersed into aqua solution of H2SO4 at 80 °C temperature up to 3 h where pH value 1 is maintained. The corroded surfaces are characterized by SEM, XRD, ATR, EDS and Tafel extrapolation methods. Results show that the corrosion under static condition is higher than that of dynamic condition both for coated and uncoated surfaces. The coated steels exhibit lower corrosion in comparison of uncoated steels. The low carbon steel experiences significant corrosion resistance property in combined effects of dynamic environment and coating surface. Corrosion rate is calculated by following weight loss method. The corrosion damage is remarkably high for low carbon steels. The nickel-plating steel exhibits more corrosion resistance in H2SO4 corrosive medium when comparing with chrome plating steel. On the other hand, chrome plating steel happens more corrosion resistance in comparison of galvanized steel. Besides, lower flow rate makes higher rate of corrosion and lower depth of penetration. It is expected that the outcomes of this work will contribute to the improvement of different concerned mechanical and tribological processes where the corrosion concerning issue.

The Effect of Boron Addition on the corrosion behavior of Ni Cr Modental alloy prepared by powder metallurgy.

The powder metallurgy (PM) method was used to create the alloy. The sintering process was carried out in an inert high-temperature tube furnace in the presence of inert gas at a temperature of 1000 ° C for 8 hours (Argon). In this article, the effect of (B) at three wt.% (0.4,0.8,1.2) on the corrosion rate, hardness, and microstructure of alloys was examined. X-ray diffraction (XRD), open circuit potential, electrochemical tests (Tafel extrapolation method), and Macro hardness Brinell were used to study the effect of adding (B) in various amounts to alloys. Saliva was utilized as the corrosion solution for the testing. The inclusion of the alloy element (B) increased hardness and a decrease in particle size, as seen by the microstructures. Furthermore, the corrosion resistance of the master alloy improved next the addition, as shown by Corrosion potential has increased while corrosion current densities have decreased. The corrosion rate for A, A1, A2 and A3 was 14.50, 7.42, 2.03and 2.77 (mpy) respectively.

On the Corrosion behavior of 4A and 5A cast duplex stainless steel under different heat treatment conditions

In this analysis, corrosion efficiency and mechanical properties of duplex stainless steel castings (DSS-4A and DSS-5A) were compared to their wrought counterparts. Cast duplex stainless steel DSS-4A and DSS-5A are characterized in two separate solution treated settings, while their wrought counterparts are characterized in both solutions treated and forged form. Optical microscopy and X-ray diffractometry were employed to perform the metallurgical characterization. Electrochemical techniques such as Tafel extrapolation and electrochemical impedance spectroscopy were used to investigate corrosion activity. An electrochemical workstation was used to perform the corrosion studies. To compare the stability and changes in corrosion properties of both grades, an ASTM standard B117 salt spray test was performed in a 3.5 percent NaCl medium. Without any intermetallic phases, the XRD showed austenite and ferrite phases. The elements were partitioned further into the phases that they promoted, according to the elemental study of the phases. The ultimate tensile strength and hardness values of DSS-5A are higher than those of DSS-4A. DSS-5A had a higher corrosion resistance than DSS-4A. When comparing the two media used (H2SO4 and NaCl), DSS-5A demonstrated superior corrosion resistance.

Test of inhibitors for preventing corrosion of steel reinforcement in concrete

Abstract Concrete is more widely used than any other manmade material. The objective of this paper is to investigate the behavior of reinforced cement when migration corrosion and guar gum inhibitors are used. The concrete samples were exposed in aggressive media H2SO4 1 M and in the presence of 1∙10-3 M Cl-. Electrochemical measurements such as half-cell potential, polarization resistance and Tafel extrapolation methods were performed in order to obtain information on the corrosion behavior of the reinforcing steel in cement mortar. Results demonstrate high resistance polarization and low corrosion rate for concrete sample with inhibitor. The corrosion rate decreases approximately 95% in presence of locust bean gum and 80% in presence of migration inhibitor.

Influence of the diffusion annealing process in the corrosion susceptibility of cobalt boride layer immersed in Hank's solution

The corrosion susceptibility of borided CoCrMo alloy exposed to a diffusion annealing process (DAP) and immersed during 7 days in a Hank's solution was evaluated, being compared with the results obtained in the borided CoCrMo alloy and the CoCrMo alloy. Firstly, the CoCrMo alloy was exposed to the powder-pack boriding process during 5 h at 1273 K, to obtain a biphasic layer (CoB-Co2B) with a total thickness around 33 μm. Then, the DAP was performed on the borided CoCrMo alloy during 2 h at 1273 K in an inert argon atmosphere to obtain a 29 μm of monophasic Co2B layer. The corrosion tests were performed by the potentiodynamic polarization technique to estimate the corrosion resistance (Rp) and the corrosion current density (jcorr) by means of the linear polarization and the Tafel extrapolation techniques, respectively. The results showed, in the 7th day of immersion in the Hank's solution, that the borided CoCrMo alloy exposed to the DAP exhibited a corrosion value ~22 times higher (~357 kΩ cm2) than that obtained in the borided CoCrMo alloy (~15 kΩ cm2), reaching a value close to the CoCrMo alloy (~385 kΩ cm2). The corrosion performance of the borided CoCrMo alloy exposed to the diffusion annealing process was attributed to i) the presence of the monophasic Co2B layer and high contents of Cr and Mo on the outer-zone of the borided surface, and ii) the depletion of the B2S3 and CrPO4 species at the surface of the borided CoCrMo alloy. Finally, the borided CoCrMo alloy exposed to the DAP exhibited a corrosion susceptibility around 7%, meanwhile the borided CoCrMo alloy obtained a value of 96%, approximately.

Effect of low-temperature annealing on the superelastic response and electrochemical corrosion behaviour of equi-atomic Ni-Ti alloy

ABSTRACT Nickel–Titanium (Ni–Ti) alloys have exemplary properties such as good thermo-mechanical response and biocompatibility. Hence, they are one of the prime materials of interest in today’s context for the fabrication of advanced biomedical devices. Such properties can be exemplified with certain techniques such as heat-treatment techniques. However, peer-reviewed literature for the same appears to be inadequate to efficiently quantify the effect of such techniques on the overall performance of such materials. Therefore, the present study focuses on analysing the effect of low-temperature heat treatment on the superelastic behaviour and corrosion resistance of titanium-rich Ni–Ti alloys. The superelastic behaviour has been evaluated for different strains. Meanwhile, the Tafel extrapolation method is incorporated to assess the electrochemical corrosion of these materials. It is noticed that the low-temperature heat treatment has marginal effects on the superelastic behaviour of the alloy. The Ni–Ti alloy annealed at 450°C at 6% predetermined strain rate showed the best enhancement in the superelastic behaviour and the corrosion resistance increased upto treatment temperatures of 350°C. Therefore, the most optimum temperature of annealing is found to be 350°C, resulting in about 35.72% improvement in the corrosion resistance of the alloy when compared to their untreated counterparts.

Effect of Surface Finishing on Microstructure and Corrosion Behavior of Friction Stir Welded Joints For Dissimilar Aluminum Alloys (AA2024-T3 with AA6061-T6)

The aim of this work is to study the possibility of joining two plates from aluminum alloys, AA2024-T3 with AA6061-T6, using friction stir welding (FSW) technique. In this study, the plates were prepared by cutting with dimensions (100 x 50 x 5) mm by CNC milling machine with cutting speed of 1200 rpm and variable feeding speed of (25, 30, 35 & 40 mm/min). The FSW was operated by a vertical milling machine at a rotary speed of 930 rpm and linear welding speed of 30 mm/min to obtain welding joints of dissimilar plates. Microstructure, surface roughness and micro-hardness were examined. Corrosion test was also carried out by electrochemical methods for all specimens in 3.5wt % NaCl solution, and the corrosion rate was calculated by Tafel extrapolation method. The obtained results demonstrated that the feeding speed has a significant effect in decreasing the corrosion rate comparing with the base metal due to the plastic deformation that occurs at high feed speed. The decrease in surface roughness provided more connected between the two contact surfaces that contributed in the refinement of the microstructure. The sample welded at feed speed 40 mm/min offered the optimum results.

A Real Time Electrochemical Analysis of Co-Sputtered (Co-Cr) and (Co-Cr-Mo) Alloy Thin Film Libraries in Ringer’s Solution at 37 oc

Cobalt-based alloys are used as total hip replacement prostheses due to their exceptional tribocorrosion properties in the human physiological environment[1]. Due to continuous mechanical and corrosive conditions, the dissolution of Cr and Co in the body fluid is unavoidable. These metallic particles and ions can cause cancer and gene mutation in the body, therefore their leaching should be diminished by proper passivation[2].In this work, two combinatorial thin film libraries namely a binary Co-Cr and a ternary Co-Cr-Mo were prepared by means of co-sputtering. Both libraries were characterized by state of the art high resolution scanning electron microscopy (SEM) and X-ray diffraction (XRD). The chromium content for binary Co-Cr library varied from 14-40 at.% (balanced Co) while for ternary Co-Cr-Mo library a compositional spread of Co (46-79 at.%), Cr (17-48 at.%) and Mo (3-11 at.%) was obtained. In both libraries roundish spike shaped grains were revealed at high cobalt content which gradually changed to refined and compact grains with the increment of Cr. Similarly, molybdenum (>-7 at.%) brought additional grain refinement. Furthermore, weak, and broad XRD peaks of rt HCP and ht FCC pure Co were disclosed at nearly all compositions. No intermetallic phase was determined in either library.The real time electrochemical screening and corrosion stability were accomplished by a in house-built flow type scanning droplet cell microscope (FT-SDCM) in conjunction with an inductively couple plasma optical emission spectroscope (ICP-OES). Various electrochemical techniques i.e. open circuit potential, linear sweep voltammetry and Tafel extrapolation were utilized. No significant passive behavior was obtained for the alloys containing the Co content higher than (68-70 at.%) irrespective of Cr and Mo concentration. However, further increment in the Cr content significantly improved the alloy nobility and restricted the active to passive dissolution. The addition of Mo improved the transpassive dissolution. A graphical model was developed on the basis of this study and a composition range of (7-10) at.% Mo and (36-48) at.% Cr (complementary Co) is recommended as likely candidate for biomedical use.

Preparation and characterization of cerium-based conversion coating on a Fe50Mn30Co10Cr10 dual-phase high-entropy alloy

The mechanical properties of the Fe50Mn30Co10Cr10 (at.%) dual-phase high-entropy alloy (DP-HEA) are superior to those of the equiatomic CoCrFeMnNi single-phase HEA. However, poor corrosion resistance due to high manganese content is one of the main factors limiting the potential applications of Fe50Mn30Co10Cr10 DP-HEAs. This study investigated the feasibility of improving the corrosion resistance of Fe50Mn30Co10Cr10 DP-HEAs through the application of a cerium conversion coating to its surface. In addition, this study investigated the effects of bath temperature and the heating process on the formation of the cerium conversion coating. A cerium conversion coating with a thickness of approximately 10–20 nm formed on the DP-HEA surface from cerium conversion baths with various continuous heating processes. The anodic current densities exhibited by the polarization curves decreased, and Tafel extrapolation revealed that the corrosion current densities of the cerium-coated specimens were two to three orders of magnitude lower than that of the untreated DP-HEA. The successful preparation of cerium conversion coatings through continuous bath-heating processes can improve the corrosion resistance of Fe50Mn30Co10Cr10 DP-HEAs. The superior anticorrosion properties of the coating formed by the T70 bath-heating process can be attributed to the increased thickness and large amount of CeO2 in the coating.

Synthesis and corrosion resistance of Cu-Al-N nanostructured thin films deposited through magnetron sputtering

Cu-Al-N thin films were deposited by means of the unbalanced magnetron cosputtering technique, varying the pulsed DC source power that is associated with the aluminum target. The structural characterization, done through x ray difraction (XRD) and transmition electronic microscopy (TEM), showed that the films were nanocrystalline, with a crystallite size of an order of magnitude of 10 nm. According to the chemical composition results, they consisted of a Cu-Al phase, copper nitride and aluminum nitride, that depended on the deposition power. The electrochemical characterization was performed by means of Tafel extrapolation and electrochemical impedance spectroscopy (EIS). The Tafel results showed a decrease in the corrosion current with an increase in the power, and the electrochemical impedance results showed an inductive behavior at low frequencies.

Comparative corrosion behaviour of stainless steels and their welds in wet-process phosphoric acid

ABSTRACT The present study compares corrosion behaviour of three austenitic stainless steels 316L, 317L and 904L (base materials and welds) in wet-process phosphoric acid (WPA) and reagent grade phosphoric acid with impurities, e.g., Cl-, F- and SO4 2-. The corrosion study was done by performing electrochemical polarisations at 50°C followed by Tafel extrapolation. Welds always had higher corrosion rates than their respective base materials. The corrosion rates of stainless steels in plant WPA were much less compared to that in reagent grade phosphoric acid with almost similar levels of Cl−, F− and . This is due to the presence of a variety of dissolved metallic ions in WPA that reduces its corrosiveness. Among the three metallic cations (Fe3+, Mg2+ and Al3+) examined in this study, the inhibiting action increased in the order Fe3+ < Mg2+ < Al3+. SS 904L was the most corrosion-resistant alloy in WPA followed by SS 317L and 316L.

ELECTROCHEMICAL PERFORMANCE OF Fe-Cr-Ni ELECTRODE AS CATHODE FOR HYDROGEN EVOLUTION IN KOH SOLUTIONS

Electrocatalytic behavior of commercially available Fe-17Cr-14Ni alloy as a cathodic material for the evolution of hydrogen in alkaline solutions has been characterized by means of microstructural and electrochemical techniques. The microstructure of the alloys was examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The electrochemical behavior of the examined materials was studied through potentiodynamic polarization techniques and electrochemical impedance spectroscopy (EIS). The effect of electrolyte concentration on the hydrogen evolution reaction (HER) rate and the cathode's electrochemical stability were studied. Tafel extrapolation method was used to determine the kinetic parameters characteristic of the hydrogen evolution reaction. The results show that the investigated alloy can be seen as a good candidate for large-scale and long-term hydrogen evolution. The rate of evolution of hydrogen under low overpotential is relatively high.

Study on the free corrosion potential at an interface between an Al electrode and an acidic aqueous NaCl solution through density functional theory combined with the reference interaction site model

We investigated the free corrosion potential at an interface between an Al electrode and an aqueous NaCl solution (NaCl(aq)) under acidic conditions via density functional theory combined with the effective screening medium and reference interaction site model (ESM-RISM). Firstly, the electrode potentials for the anodic and cathodic corrosion reactions were obtained from the grand potential profile as a function of the electron chemical potential at the interface. Thereafter, we determined the free corrosion potential using the Tafel extrapolation method. The results of the free corrosion potential were consistent with previous experimental data. By controlling the pH of the NaCl(aq), we determined the pH dependence of the free corrosion potential, and the results reasonably reproduce the previous experimental results. Our results indicated that the ESM-RISM method duly described the environmental effect of an acidic solution and precisely determined the free corrosion potential. Therefore, the application of this method presents an efficient approach toward calculating the free corrosion potential for various reactions.

Effect of Martensite Morphologies on Corrosion in 5% H2SO4 Solution of Borided X70 Dual Phase Steel

In the present investigation, some electrochemical properties of dual phase X70 steels with different martensite morphologies which have undergone boriding were studied. To obtain a variety of martensite morphologies, Direct Quenching (DQ), Intermediate Quenching (IQ) and Step Quenching (SQ) heat treatments were applied at an intercritical annealing temperature (IAT) of 760℃. The treatment (DQ) allowed the formation of fine martensite evenly distributed in the ferrite matrix. (IQ) treatment showed the formation of martensite along the ferrite / ferrite grain boundaries. In contrast, treatment (SQ) induced the formation of a banded morphology of martensite and ferrite. The realization of borides on X70 (DP) steel was carried out in a powder mixture containing 5% of B4C as source of boron, 5% of NaBF4 as activator and 90% of SiC as diluent at 950℃ for a period of time from 4 h. The corrosion behavior of X70 (DP) steel has been explored by the Tafel extrapolation method in a 5 wt. % H2SO4 solution. The corrosion resistance of steel which has undergone boriding (BDP) is higher than that of steel which has not undergone it (DP).