Potentiodynamic Technique Research Articles

Wet Etching Behavior of Amorphous CuZr Thin Film in Hydrogen Peroxide Solution for Stretchable Display

Stretchable displays, a key benchmark for the next generation of display technologies, will be bendable, foldable, flexible and use a stretchable copper film. Amorphous CuZr has been selected for the copper metallization of the stretchable display due to its excellent elongation properties compared to conventional metals. However, little is known about the etching mechanism for amorphous CuZr and copper in a hydrogen peroxide solution containing fluorine ions. In this paper, the wet etching behavior of amorphous Cu50Zr50 thin films in a hydrogen peroxide-based copper wet etchant is studied using an electrochemical potentio-dynamic technique and surface analysis. An anodic Tafel slope of approximately 30 mV/decade is obtained. A new dissolution mechanism in the presence of 0.1 M fluoride ions in hydrogen peroxide solution is suggested. It should be noted that the wet etching rate of amorphous CuZr is strongly dependent on the existence of fluoride ions in the wet etchant.

Corrosion behavior of Electro-deposited Ni-Cr2O3/SnO2 coatings on mild steel

The increasing use of mild steel in diverse environments and under different conditions requires the increased interest in research into these groups of specific steels with attention to their moderate corrosion rate and performance. The electrochemical study of Ni-Cr2O3/SnO2 coating was studied using potentiodynamic techniques. The microhardness properties of the deposits were studied using Emco microhardness tester. The effect of Cr2O3/SnO2 on nickel-based coatings was investigated to analyze the corrosion resistance of the coating by using the polarization method. The result indicates a reduction in corrosion rate with the addition of Cr2O3/SnO2 and the hardness of the coated sample also reduced drastically with the addition of SnO2 to the bath.

The Chemical and Biological Properties of Nanohydroxyapatite Coatings with Antibacterial Nanometals, Obtained in the Electrophoretic Process on the Ti13Zr13Nb Alloy.

The risk of an early inflammation after implantation surgery of titanium implants has caused the development of different antimicrobial measures. The present research is aimed at characterizing the effects of nanosilver and nanocopper dispersed in the nanohydroxyapatite coatings, deposited on the Ti13Zr13Nb alloy, and on the chemical and biological properties of the coatings. The one-stage deposition process was performed by the electrophoretic method at different contents of nanomaterials in suspension. The surface topography of the coatings was examined with scanning electron microscopy. The wettability was expressed as the water contact angle. The corrosion behavior was characterized by the potentiodynamic technique. The release rate of copper and silver into the simulated body fluid was investigated by atomic absorption spectrometry. The antibacterial efficiency was evaluated as the survivability and adhesion of the bacteria and the growth of the biofilm. The cytotoxicity was assessed for osteoblasts. The results demonstrate that silver and copper increase the corrosion resistance and hydrophilicity. Both elements together effectively kill bacteria and inhibit biofilm growth but appear to be toxic for osteoblasts. The obtained results show that the nanohydroxyapatite coatings doped with nanosilver and nanocopper in a one-stage electrophoretic process can be valuable for antibacterial coatings.

Erosion-corrosion assessment in strong acidic conditions for a white cast iron and UNS S31600 stainless steel

In mining industry, various parts of pumps such as liners and impellers are deteriorated severely due to erosion-corrosion mechanisms reducing the productivity of mining process and the transportation of extracted ores. It has been found that some mines consist of chlorides, very low pH and abrasive erodent particles which enhance the materials degradation. Two groups of alloys that are attractive for those aggressive slurries are white cast irons and stainless steels. In the present study, the erosion-corrosion performance of a hypoeutectic white cast iron with austenitic matrix (37 WCI) and UNS S31600 stainless steel was investigated. The testing apparatus used submerged jet technique and the angle of impingement was the normal incidence. The tests in solid/liquid impingement were conducted in aqueous solution with 3.5% NaCl with silica angular sand at pH 0. The results revealed that 37WCI was superior to UNS S31600, whilst the proportional damage of pure erosion, pure corrosion and their synergistic effects were investigated thoroughly. Detailed analysis was obtained by implementing cathodic protection (CP), potentiodynamic techniques, surface topography and microscopy. The erosion-corrosion phenomena were also analysed in different regions of the tested surface in order to understand how they affect the materials' performance in different hydrodynamic zones. It was found that corrosion was a crucial factor for the alloys’ performance, rather than their wear resistance. In addition, both alloys experienced higher corrosion rates in regions where the mechanical damage was enhanced.

PROTECTIVE BEHAVIOR AGAINST CORROSION OF POLY(N-METHYLANILINE) COATINGS ELECTROSYNTHESIZED ON STAINLESS STEEL SURFACE FROM SULFURIC ACID CONTAINING MONOMER SOLUTION

Poly(N-methylaniline) coated stainless steel disc electrodes were obtained with N-methylaniline containing sulfuric acid solutions using constant potential, constant current and potentiodynamic techniques by electrodeposit method. Corrosion behavior of polymer coated electrodes were investigated by direct current (DC) polarization technique and linear anodic cyclic voltammetry in different aqueous (NaCl and HCl) solutions.

Pitting Suppression of AISI 316 Stainless Steel Plates in Conditions of Ultrasonic Vibration

Plate heat exchangers are widespread type of equipment that suffers from pitting corrosion in chloride containing solutions. Anodic behaviour of AISI 316 stainless steel was tested in 3.5% NaCl solution in conditions of ultrasound vibration (27 kHz, 10 W). The potentiodynamic sweep, potentiostatic technique, and galvanostatic technique were used coupled with surface morphology investigation after polarization. The pitting potential increased from 0.26 ± 0.02 V/SSCE to 0.42 ± 0.05 V/SSCE, and repassivation potential increased from 0.03 ± 0.01 V/SSCE to 0.18 ± 0.04 V/SSCE when vibration was applied. The anodic current at applied potential in pitting region was two orders of magnitude lower in conditions of ultrasound vibration. A possible mechanism of vibration influence on pitting is proposed, which is the elimination of pit covers from the vibrating surface, vibration-induced electrolyte motion in and out of the pits, and repassivation of active metal inside the pits.

Water-Induced Corrosion Damage of Carbon Steel in Sulfolane

Sulfolane in contact with water and oxygen forms acidic (by-) products that are major factors in accelerating the corrosion of carbon/stainless steel. In consequence, water-induced corrosion damage can be a serious problem in industrial systems. Hence, the determination of the corrosion resistance of AISI 1010 steel immersed in sulfolane containing 0 to 6 vol.% water was the principal objective of the study. Evaluation of the corrosion resistance of steel electrodes was performed using a potentiodynamic technique and scanning Kelvin probe microscopy. It was observed that the corrosion products layer that formed on the surface of AISI 1010 steel partially protects it against corrosion in sulfolane with a water concentration in the range from 1 vol.% to 4 vol.%. Interestingly, amounts of water above 4 vol.% cause a break-down of the corrosion products layer and deteriorate the corrosion resistance of AISI 1010 steel as well. Moreover, the relationship between the fractal dimension, corrosion degree of the steel surface and water concentration in sulfolane was investigated. The fractal dimension was determined using 2D grayscale images of AISI 1010 steel registered through a scanning electron microscope. It was noticed that both the fractal dimension and the corrosion degree rose with the increased water concentration in sulfolane.

Electrochemical Approaches for Material Conservation: Experimental and Theoretical Insights Using a Biopolymer

Maltodextrin (MLD) is introduced as a novel, potent green inhibitor for the corrosion control of zinc in 0.1 sulfamic acid. The corrosion and inhibition studies were done by electrochemical techniques such as potentiodynamic polarisation measurements and electrochemical impedance spectroscopy technique. Conditions were optimised to get maximum inhibition efficiency by varying the concentration of the inhibitor in the temperature range of 303–323 K. Activation and thermodynamic parameters were evaluated and discussed in detail. Suitable mechanism was proposed for corrosion and inhibition process. Surface characterisation was done by SEM, EDX and AFM techniques before and after the addition of inhibitor. The density functional theory calculations were performed and compared with experimental observations. Results indicated that inhibition efficiency increased with the temperature and inhibitor concentration. Maximum inhibition efficiency was found to be 62.3% for the addition of 0.4 g L−1 MLD. Theoretical calculations confirmed the experimental observations.

Inhibition of Mild Steel Corrosion in 1M Hydrochloric Medium by the Methanolic Extract ofAmmi visnagaL. Lam Seeds

The chemical composition of the methanolic extract ofAmmi visnaga(Khella) seeds from the Sidi Slimane region is determined for the first time by Gas Chromatography coupled with Mass Spectrometry (GC/MS). Ten compounds representing 99.638% of the total extract were identified. Khellin (49.011%), Visnagin (26.537%) and Dimethylethylamine (15.108%) are the major components. Moreover, the inhibitory effect of the Methanolic extract of the seeds ofAmmi visnagaon the corrosion of mild steel in a solution of 1M HCl is determined using weight loss measurements, the potentiodynamic technique as well as the technique of electrochemical impedance spectroscopy (EIS). It is found that the extract reduces the corrosion rate of the steel in the acid solution. Inhibition efficiency increases as the concentration of the extract increases. The tested compound has an inhibition efficiency of 84% for a concentration equal to 1.0 g/L. The polarization measurements indicate that the examined extract acts as a mixed inhibitor with predominant anodic efficacy. The data obtained from EIS studies are analyzed to model this process using appropriate equivalent circuit models. The adsorption of the extract on the surface of the mild steel obeys the Langmuir adsorption isotherm in acidic medium and the activation is determined and discussed.

Complementary electrochromic devices of PANI and PEDOT using the enzymatic poly(gallic acid)

The semiconducting and non-toxic enzymatic polygallic acid (PGAL) produces water dispersible poly(3,4-ethylenedioxythiophene) (PEDOT-PGAL) and polyaniline (PANI-PGAL). The results indicate that PGAL is a template for the model polymers, and thereby, the complexes are processable by spray coating to produce flexible electrochromic devices (ECDs). The materials were characterized by infrared spectroscopy, thermogravimetric analysis, and conductivity measurements in pellet form. Additionally, potentiostatic and potentiodynamic techniques in combination with UV-spectroscopy assess these materials. The produced ECDs based on PEDOT-PGAL has a ΔT of up to 19% and a life span lower than 100 cycles. However, when the PEDOT-PGAL architecture is complementary with PANI-PGAL displays up to 1000 times with a ΔT of 15% and coloring efficiencies of 275 cm2/C. The color of this PGAL-based device changes from dark violet to light green which differs from the common complementary EDCs. Additionally, complementary ECD fabricated with PEDOT-PSS against PANI-PGAL enhances the coloring efficiency up to 517 cm2/C (ΔT = 26%) and cycled 1000 times.

Ni/Ni-Cr-P and Ni/Ni-Mo-Cr-P Electrodeposited Coatings As Bipolar Plate in Polymer Electrolyte Membrane Fuel Cell Environment

Polymer electrolyte membrane (PEM) fuel cells are expected to play a major role in transporting humans and goods. However, one of major bottlenecks is the high materials and manufacturing cost. One way to lower the cost to a great extent is by replacing conventional graphitic bipolar plates with metallic bipolar plates (BPPs), as they costs around 30% of the total cost of stack1. That said, metallic BPPs have durability issues. Over time, they corrode and show higher interfacial contact resistance (ICR). In this work we attempt to engineer the surface of metallic BPPs, so that they perform for longer duration without degrading. To keep the process economical and commercially attractive, a bilayer coating of Ni followed by Ni-Cr-P alloy is pulsed electrodeposited on AISI 1020 low carbon steel. The electrodeposition process is optimized varying the process parameters, such as electrolyte composition, temperature and deposition current. Field emission scanning electron microscopy and energy dispersive x-ray spectroscopy are used to study the surface morphology and compositional analysis of coating, respectively. Variation in microstructure and composition the Ni/Ni-Cr-P coating is observed with change in process parameter such as pH and temperature. Corrosion studies were carried out on Ni/Ni-Cr-P coated samples using potentiodynamic technique in accelerated (0.5 M H2SO4 + 2 ppm HF) solution at 80ºC. Ni/Ni-Cr-P coated samples with higher Cr content exhibited better corrosion resistance behaviour in both cathodic (air-purging) as well as anodic (H2-purging) environment compared to the bare substrate. Long term durability of Ni/Ni-Cr-P coated samples and AISI 1020 low carbon steel samples were studied using potentiostatic polarization technique. Both coated and bare samples are placed in the accelerated electrolyte solution. Ni/Ni-Cr-P coated samples showed better durability with less change in current density, while bare samples completely disintegrate and precipitate into the solution within 2–3 hours in potentiostatic mode in both the environments. Ni/Ni-Cr-P coated sample show lower interfacial contact resistance (ICR) value than that of bare AISI 1020 steel samples. For better corrosion resistance and improvement in surface electrical property, Mo was included in the coating composition2. Ni/Ni-Mo-Cr-P coated samples show improved corrosion resistance than Ni/Ni-Cr-P coated samples and AISI 1020 low carbon steel bare samples in both anodic and cathodic PEM fuel cell environment. Reference: R. Taherian, J. Power Sources, 265, 370–390 (2014) http://dx.doi.org/10.1016/j.jpowsour.2014.04.081.H. Rashtchi et al., Fuel Cells, 16, 784–800 (2016) http://dx.doi.org/10.1002/fuce.201600062

Evaluation of Corrosion Resistance of Corrosion Inhibitors for Concrete Structures by Electrochemical Testing in Saturated Ca(OH)2Solutions with NaCl and Na2SO4

Reinforcing steel maintains passivity in an alkaline concrete environment. However, the passive film on the steel can be destroyed as the concrete becomes acidic, which could induce the corrosion of reinforcing steel. Carbonates and sulfates destroy the concrete matrix and accelerate the penetration of hazardous ions, thereby deteriorating the structure. To alleviate the corrosion of internal reinforcing steel within concrete, corrosion inhibitors are most widely used. In this study, the effects of inorganic nitrite (lithium nitrite) and amino acid corrosion inhibitors (diethanolamine, methyl diethanolamine, and 4-aminobutyric) on corrosion resistance and the pH of the solution with various concentrations of Na2SO4(0.89, 1.77 g/L) in saturated Ca(OH)2that contained NaCl (0.98 g/L), which simulated the concrete environment, were investigated. The corrosion resistance of inhibitors was evaluated by corrosion potential, electrochemical impedance spectroscopy, and potentiodynamic techniques. The results indicated improvement of corrosion resistance by the addition of amino acid corrosion inhibitors. It was confirmed that the inhibitor adsorbed on the surface of the specimen and passivated to reduce the corrosion reaction. In addition, the 4-aminobutyric acid corrosion inhibitors had the corrosion protection efficiency of 67.87–77.80%, which is a higher value than that of the inorganic nitrite corrosion inhibitor (lithium nitrite: 69.36–75.93%) and other amino acid corrosion inhibitors (diethanolamine: 35.69–39.91%; methyl diethanolamine: 66.07–69.09%).

Carbon Fiber/Polyaniline as a High Performance Electrode for a Symmetrical Supercapacitor

The single and multilayered electrode materials having carbon fiber and polyaniline were prepared. The variation of morphological and electrochemical properties of electrode materials was studied in three different electrolytes. The electrode materials were prepared by taking stainless steel as the substrate using the potentiodynamic technique. The electrode materials were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and N2 adsorption/desorption measurement. The supercapacitor characteristics of these electrode materials were analyzed using cyclic voltammetry, ac impedance, and charge–discharge cycling techniques. It was found that multilayered electrode material resulted in a specific capacitance value of 350 F/g during charge–discharge cycling studies

Poly 1,5 diaminonaphthalene supported Pt, Pd, Pt/Pd and Pd/Pt nanoparticles for direct formic acid oxidation

Comparative studies were carried out on the direct electrooxidation of formic acid at palladium (Pd), platinum (Pt), Pt/Pd and Pd/Pt nanoparticles (NPs) supported on poly 1,5‑diaminonaphthalene (PDAN)-modified glassy carbon electrode. Metal electro-deposition was carried out using potentiodynamic technique. Cyclic voltammetry (CV), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) have been used to investigate the electrochemical behavior, surface morphology and chemical composition of the studied electrodes. Electrode's electroactive surface area has been determined by electrooxidation of pre-adsorbed CO monolayer using the coupling of the dual thin layer flow through cell with mass spectrometer. Electrooxidation of formic acid (FA) at different modified electrodes have been studied using the differential electrochemical mass spectroscopy (DEMS) protocol and the current efficiencies with respect to CO2 evolution were calculated. NPs incorporated PDAN polymer films improved the electrocatalytic efficiency towards the electrooxidation of FA. Among the studied electrodes, Pt/Pd/PDAN/GC shows the best metal dispersion and highest electrocatalytic activity towards formic acid oxidation (FAO).

Influence of pre-grafted pyrrole-based silane on the electrodeposition and chemical properties of polypyrrole films

The functionalization of fluorine-doped tin oxide (FTO) substrates by a pyrrole-based silane and subsequent electrodeposition of polypyrrole films on the modified substrates has been achieved. First, N-[3-(trimethoxysilyl)propyl]pyrrole (TMSP) was successfully grafted on FTO substrates as evidenced using X-ray Photoelectron spectroscopy and Glow Discharge Optical Emission Spectroscopy. Second, polypyrrole was electrochemically prepared onto silanized (PPy/TMSP/FTO) and non-silanized (PPy/FTO) substrates, using potentiostatic and potentiodynamic techniques, in order to study the effect of silanization on the polypyrrole growth. Cyclic voltammetry experiments indicated that the growth of the polypyrrole films and their electrochemical activity weren’t strongly affected by the presence of a silane layer. On the contrary, the morphology of the PPy films was very different with and without the layer of silane since PPy/TMSP/FTO films were strongly less rough and more uniform than PPy/FTO films. The morphology of these new films was also granular and composed of globules having a submicrometric size. The lower roughness of the PPy/TMSP/FTO films, compared to the PPy/FTO ones, affected their wettability leading to a lower surface energy and more hydrophobic behavior. The conductivity of the PPy films was proved to be higher on unmodified FTO substrates by using conductive AFM experiments. Finally, the improvement of the adhesion of the polypyrrole films onto the FTO substrate, thanks to the silanization, was evidenced by immersing the modified FTO substrates in water for several weeks.

Effect of Destabilisation and Tempering Heat Treatments on Hardness and Corrosion Behavior of 28 wt.%Cr Cast Irons with Mo Addition

The effects of destabilisation and tempering heat treatments on hardness and corrosion behavior in 28 wt.%Cr-2.6 wt.%C cast irons with up to 6 wt.%Mo addition were studied. The irons were destabilised at 1025 °C for 4 h and air cooled. Tempering was carried out at 450 °C for 4 h. Phase identification and microstructure were investigated by X-ray diffraction (XRD), light microscope (LM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Vickers macro-hardness was measured. A potentiodynamic technique was used to indicate aqueous corrosion resistance. The results revealed that the as-cast microstructure of 28 wt.%Cr iron consisted of primary austenite dendrites with eutectic M7C3 carbides. In the irons with 6 wt.%Mo addition, eutectic carbides including M7C3, M23C6 and M6C were found. After destabilisation, the microstructure contained secondary carbide precipitates within an essentially martensitic matrix. Vickers macro-hardness of the as-cast and destabilised irons increased from 500 HV30 and 736 HV30 in the 28 wt.%Cr iron up to 570 HV30 and 870 HV30 in the iron with 6 wt.%Mo addition. Tempering slightly increased the macro-hardness. The as-cast 28 wt.%Cr iron had the lowest values for critical current density and passive current density. The destabilised + tempered treatment gave the lowest corrosion resistance.

A critical examination of corrosion rate measurement techniques applied to reinforcing steel in concrete

This paper presents an investigation of five corrosion‐monitoring techniques for reinforced concrete. The techniques studied are the potentiodynamic, galvanostatic, and coulostatic direct‐current techniques as well as electrochemical impedance spectroscopy (EIS), and the connectionless electrical pulse response analysis (CEPRA) technique. The study included monitoring corrosion rates on reinforced concrete specimens with a range of admixed chloride percentages, cover depths, and rebar diameters for 8 months. After this period, the rebars were extracted for mass loss measurements to determine the average corrosion rates. EIS was found to provide accurate measurements of active and passive corrosion rates with a simplified spectrum‐analysis procedure. Galvanostatic and potentiodynamic techniques were able to measure the corrosion rates for actively corroding reinforcements accurately, while the coulostatic technique overestimated it. For passive reinforcements, the coulostatic technique provided reliable corrosion rate estimates, while the potentiodynamic technique provided a minor overestimation, due to the fast scan rate used, and the galvanostatic technique failed in detecting passivity, due to the short measurement duration and confinement failure. Finally, the CEPRA technique provided accurate corrosion rate predictions except for passive rebars with small diameters embedded in saturated concrete.

Electrosynthesis of Bromothiophene and Thiophene as Conducting Copolymer and Study of their Electrochemical Relaxation

The electrosynthesis of the copolymer of 3-bromothiophene and thiophene has been investigated using galvanostatic and potentiodynamic techniques. The most stable films were obtained using the galvanostatic technique in nitrobenzen solvent and TBAPF6 as supporting electrolyte. A comparison study was performed for the prepared copolymer and homopolymer films that were subjected to relaxation studies using the cyclic voltammetric technique in different solvents. The effect of solvent, monomer concentration ratio, electrocopolymerization techniques and temperature on the relaxation time were investigated.

Electrochemically synthesised xanthone-cored conjugated polymers as materials for electrochromic windows

In this work, we present the electrochemical polymerisation process of triarylamine-xanthone derivatives and behaviour of the formed polymers using various potentiodynamic techniques. The formed electropolymers have limited conjugation but show very promising electrochromic behaviour. Furthermore, by coupling the electrochemical analysis with each polymer's spectroscopic output, we were able to evaluate doping processes and the type of charge carriers formed. Through careful analysis, we were able to describe the electropolymerisation process and formed triarylamine-based polyxanthone derivatives. The polymers were found to exhibit good stability and good colouration efficiency to suggesting that they have potential application in electrochromic devices.

Assessment of Corrosion Behavior in Artificial Saliva of Wires for Orthodontic Applications

The aim of this study, the corrosion behavior of TiNiCu in artificial saliva (pH5.35) at 37°C was assessed by the use of electrochemical methods. Ti50Ni43Cu7 (at%) used in this study were made from ingots prepared by the vacuum arc melting (VAM) method. The furnace was purged with argon gas during melting. All melted ingots were then homogenized at 800°C for 3.6 ks. Open circuit potential (OCP) was monitored at 3.6 ks followed by potentiodynamic techniques. The results showed that all chemical composition of orthodontic wires by EPMA were Ti, Ni, Cu, Cr, Fe and Mn. Surface roughness was measured in order to ensure that TiNiCu and SS was significant difference which might affect corrosion resistance. It was seen that TiNiCu orthodontic wires, presented a good corrosion resistance, compared to the stainless steel, probably due to the formation of a protective oxide film mainly constituted by titanium oxide.