Galvanostatic Polarization Measurements Research Articles

Corrosion and Inhibition Effects of Mild Steel in Hydrochloric Acid Solutions Containing Organophosphonic Acid

A study has been made on the mechanism of corrosion of mild steel and the effect of nitrilo trimethylene phosphonic (NTMP) acid as a corrosion inhibitor in acidic medium, that is, 10% HC1 using the weight loss method and electrochemical techniques, that is, potentiodynamic and galvanostatic polarization measurements. Although corrosion is a long-time process, but it takes place at a faster rate in the beginning which goes on decreasing with due course of time. The above-mentioned methods of corrosion rate determination furnish an average value for a long-time interval. Looking at the versatility and minimum detection limit of the voltammetric method, the authors have developed a new voltammetric method for the determination of corrosion rate at short-time intervals. The results of corrosion of mild steel in 10% HC1 solution with and without NTMP inhibitor at short-time intervals have been reported. The corrosion inhibition efficiency of NTMP is 93% after 24 h.

Ethoxylated fatty amines as corrosion inhibitors for carbon steel in hydrochloric acid solutions

The effect of three compounds of non ionic surfactants, namely, ethoxylated fatty amines with different number of ethylene oxide unit on the corrosion of carbon steel (Type L52) in 1 M HCl has been studied using weight loss and galvanostatic polarization measurements. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitor, number of ethylene oxide units and with decreasing temperature. The inhibitive effect of these compounds was interpreted in view of their adsorption on the steel surface, through their ethoxy groups. The adsorption of these compounds was found to obey the Langmuir isotherm. The effect of temperature on the rate of corrosion in the absence and presence of these compounds was also studied. Some activated thermodynamic parameters were calculated.

Inhibition of carbon steel corrosion in hydrochloric acid solutions using polyoxyethylene sorbitan fatty acid esters (tween compounds)

Inhibition of carbon steel corrosion in 1 M hydrochloric acid solution in the presence of some polyoxyethylene sorbitan fatty acid esters (Tween compounds) is studied by weight loss and galvanostatic polarization measurements. The inhibition efficiency increases with increasing surfactant concentration and decreasing temperature. The inhibiting effect of the investigated compounds is explained by their adsorption on the metal surface. The adsorption process is described by a Langmuir isotherm. The effect of rising temperature on the steel corrosion rate in the absence and in the presence of the inhibitors is investigated. Some thermodynamic corrosion parameters are calculated.

Electrobioremediation of Patagonian Soils Contaminated with Hydrocarbons

The effect of 2-amino-4,6-dihydroxy pyrimidine (ADHP) on the corrosion of carbon steel in 1 M HCl has been studied using weight loss and galvanostatic polarization measurements. The percentage inhibition efficiency was found to increase with increasing concentration of the inhibitor, and with decreasing temperature. The inhibitive effect of these compounds was explained on the basis of the formation of an insoluble complex adsorbed on the metal surface. The adsorption process follows Langmuir adsorption isotherm. The effect of temperature on the rate of the corrosion in the absence and presence of these compounds was also, studied. The activated thermodynamic parameters were calculated and explained.

Effect of some amidopoly ethylamine on corrosion of zinc electrode used in zinc-manganese batteries

The effect of addition of some amidopoly ethylamine, with different numbers of ethylamine units, on the corrosion of zinc electrode in 35% ZnCl2, (26% ZnCl2 + 8.8% NH4Cl), (8.8% ZnCl2 + 26% NH4Cl) and 26% NH4Cl electrolytes has been studied using galvanostatic polarization measurements and hydroden evolution reaction (HER). The effect of the addition on discharge and shelf life of Zn-manganese batteries has been studied. The results showed that the inhibition efficiency increases with increasing number of ethylamine units per molecule. Inhibition is explained on the basis of adsorption of amidopoly ethylamine molecules on the zinc electrode surface through their ethylamine groups.

중탄산소듐 용액에서 납의 부식방지제인 자연산물질들

0.1 M 중탄산소듐 용액에서 납전극부식에 대한 로소니아, 감초뿌리 및 카로브 추출물수용액의 부식방지작용에 대한것을 정전류극성방법을 사용해 연구하였다. 이들 물질들의 부식방지작용을 지적해주는 것으로 이들 물질들이 존재할 때 부식속도가 감소하는 것이 발견되었다. 부식방지효율은 추출물농도가 증가하면 증가한다. 이들 추출물의 부식방지작용은 납표면에 이들 추출물이 흡착되어 물질 및 하전이동의 장벽을 만들어 나타내는 것으로 설명되었다. 이들 추출물의 납표면에 흡착은 자발적으로 일어나며, Freundlich 등온흡착을 따르는 것으로 발견되었다. 또한, 변전위양극분극법을 사용해 이들 추출물은 염소를 포함한 용액에서 납의 움푹패이게 하는 부식으로부터 잘 보호해주는 것이 발견되었다. The inhibitive action of the aqueous extract of lawsonia, licorice root and carob toward the corrosion of tin electrode in 0.1 M <TEX>$NaHCO_3$</TEX> solutions was investigated using galvanostatic polarization measurements. It was found that the corrosion rate decreases in the presence of these extracts indicating the inhibiting of these compounds. The inhibition efficiency increases with increasing extract concentration. The inhibition action of these extracts was explained in view of adsorption of its compounds onto the tin surface, making a barrier to mass and charge transfer. The adsorption of these extracts on the tin surface was found to be a spontaneous process and follow Freundlich adsorption isotherm. It is also found that these extracts provide a good protection to tin against pitting corrosion in chloride containing solution using potentiodynamic anodic polarization technique.

Amidopoly Ethylamines as Corrosion Inhibitors for Zinc Dissolution in Different Acidic Electrolytes

The effect of some amidopoly ethylamine, with different numbers of ethylamine units, on the corrosion of zinc electrode in ZnCl 2, NH 4Cl and (ZnCl 2 + NH 4Cl) electrolytes has been studied using galvanostatic polarization measurements. The inhibition efficiency was found to increase with increasing concentration, number of ethylamine units per molecule and with decreasing the temperature. Inhibition is explained on the basis of adsorption of amidopoly ethylamine molecules on the zinc electrode surface through their ethylamine groups. The inhibitors are adsorbed on the zinc electrode surface according to Langmuir adsorption isotherm. Some thermodynamic parameters are calculated and explained for the tested systems from the data obtained at different temperatures.

Inhibiting effects of butyl triphenyl phosphonium bromide on corrosion of mild steel in 0.5 M sulphuric acid solution and its adsorption characteristics

Butyl triphenyl phosphonium bromide (BuTPPB) has been evaluated as a corrosion inhibitor for mild steel in 0.5 M H 2SO 4 solutions using galvanostatic polarisation and potentiostatic polarisation measurements. The study was also complemented by infra red (IR) spectroscopy, scanning electron microscopy (SEM) and quantum chemical calculations. Galvanostatic polarisation measurements showed that the presence of BuTPPB in aerated 0.5 M H 2SO 4 solutions decreases corrosion currents to a great extent and the corrosion rate decreases with increasing inhibitor concentration at a constant temperature. At 298K, inhibition efficiency was found to be 94.5% for 10 −7 M BuTPPB which increased to about 99% for the BuTPPB concentration of 10 −2 M. The effect of temperature on the corrosion behaviour of mild steel was studied at five different temperatures ranging from 298 to 338K. The polarisation curves clearly indicate that BuTPPB acts as a mixed type inhibitor. Adsorption of BuTPPB on the mild steel surface follows the Langmuir isotherm. Potentiostatic polarisation measurements showed that passivation was observed only for lower BuTPPB concentrations (10 −5 and 10 −7 mol l −1) for the mild steel in 0.5 M H 2SO 4. IR and SEM investigations also confirmed the adsorption of BuTPPB on the mild steel surface in 0.5 M H 2SO 4 solutions. The molecular parameters obtained using PM3 semi-empirical method, were correlated with the experimentally measured inhibitor efficiencies.

ELECTROCHEMICAL BEHAVIOR OF MOLYBDENUM ELECTRODE IN ACETIC, FORMIC AND OXALIC ACID SOLUTIONS.

The electrochemical behavior of molybdenum electrode in acetic, formic and oxalic acid solutions is studied. The effect of immersion time, composition medium, applied voltage, applied current density and scanning rate is investigated using potentiodynamic, potentiostatic and galvanostatic polarization measurements. The stability of the oxide film formed on Mo electrode is affected by both the formation medium and the applied potential. In 0.5N oxalic acid, the critical applied voltage below which the current start to oscillate is equal to -80 mV. The rate of dissolution of anodic oxide film formed on Mo in oxalic acid is very rapid compared with that formed in acetic and formic acids. Also in oxalic acid solutions Mo is notably affected by applied current density in which reciprocal capacitance, Cs-1, decrease with increasing applied current density. On the contrary in acetic and formic acids Mo did not affect. In acetic acid solution, the time of anodization has little or no effect on the dissolution process.

Aluminium-doped LiFePO4 single crystals : Part II. Ionic conductivity, diffusivity and defect model

We report on lithium ion conductivity and diffusivity along major crystallographic directions of Al-doped LiFePO4 single crystals. Impedance spectroscopy as well as galvanostatic polarization measurements have been carried out on the electronically blocking symmetric cell LiAl/LiI/LiFe(Al)PO4/LiI/LiAl. Neither ionic conductivity nor lithium diffusivity show anisotropy in the bc planes within the experimental error, but much lower values in the a-direction. Similar features were observed earlier by us for the pure single-crystal and the Si-doped single crystal. On Al-doping the ionic conductivity has increased while the electronic conductivity has decreased compared to undoped LiFePO4. Not only this donor doping effect but also the temperature dependence of ionic conductivity and of lithium-diffusivity are successfully interpreted in terms of lithium vacancies, holes and associates in the framework of a detailed defect chemical analysis. Ion-electron as well as ion-ion associates play a significant role in this system.

Effect of allyl triphenyl phosphonium bromide on electrochemical and corrosion behaviour of mild steel in 0·5M sulphuric acid

Phosphonium compounds are known to act as corrosion inhibitors of mild steel in acidic solutions. They may be added to hydraulic oils or drilling fluids to provide scale and corrosion inhibition. They can be applied on the substrate by immersion or be incorporated in a polymeric coating. In the present work, allyl triphenyl phosphonium bromide (ATTPB) is evaluated as the potential corrosion inhibitor for mild steel in sulphuric acid solutions. Galvanostatic polarisation and potentiostatic polarisation measurements were used to study the inhibition of mild steel corrosion in aerated 0·5M sulphuric acid at different temperatures by ATPPB. Corrosion potential, corrosion currents, cathodic and anodic Tafel slopes, heat of adsorption and effective activation energies have been calculated in the presence and absence of the ATPPB. Inhibition efficiency has been calculated for various concentrations at different temperatures to study the range of effectiveness of the ATPPB. It shows the inhibitor efficiencies in the range of 73 to 99% and performs best at 318 and 328 K. The nature of adsorption of ATPPB on the metal surface has also been examined using infrared spectroscopic studies. The results of surface morphology and quantum chemical analysis are in agreement with the electrochemical results.

4-(2-pyridylazo-)-resorcinol as effective corrosion inhibitor for mild steel in 0·5M sulphuric acid

The efficiency of 4-(2-pyridylazo-)-resorcinol (PAR) as corrosion inhibitor for mild steel in H2SO4 was investigated by electrochemical methods such as steady state galvanostatic and potentiostatic polarisation measurements. The dissolution parameters such as corrosion currents, passive current, flade potential, open circuit potential, cathodic and anodic Tafel slopes and efficiencies were determined. Potentiodynamic polarisation was used to assess the ability of heterocyclic organic inhibitor/PAR to provide an effective barrier to corrosion in acidic environments. Electrochemical measurements showed that the heterocyclic compound investigated has a fairly good inhibiting properties. The absorption and corrosion rates based on heat of adsorption and activation energies are calculated from Langmuir’s adsorption isotherm. The inhibition efficiency range of 84–93% is obtained for a concentration range of 10−7–10−1 mol L−1. Passivating parameters revealed that this inhibitor is strongly passivating. Scanning electronic microscopy observations and quantum chemical calculations along with the electrochemical data suggested that the ability of PAR to act as a physical barrier was more important in providing corrosion protection of mild steel surface against acidic environments.

Corrosion inhibition of mild steel in acidic medium by some sulfa drugs compounds

The inhibiting effect of four sulfa drugs compounds (e.g. sulfaguanidine, sulfamethazine, sulfamethoxazole and sulfadiazine) on mild steel corrosion in 1.0 M HCl solutions were evaluated using both galvanostatic polarization and weight loss techniques. All the examined sulfa drug compounds reduce the corrosion of mild steel. Among the compounds studied, sulfadiazine exhibited the best inhibition efficiency and sulfaguanidine the lowest. The inhibition efficiency goes through a maximum for sulfaguanidine while it increases continuously with concentration to a limit with sulfadiazine, sulfamethoxazole and sulfamethazine respectively. Galvanostatic polarization measurements indicate that all the examined compounds are of mixed inhibitor type with predominant cathodic effectiveness. Moreover, the results revealed a better performance for these compounds as corrosion inhibitors in HCl than in H 2SO 4 solutions. Also, the corrosion inhibition mechanism is discussed.

Inhibition of acidic corrosion of iron by some Carrageenan compounds

The corrosion inhibition of some sulfated water soluble natural polymer (carrageenan) compounds on the corrosion of iron in 1M HCl was studied using weight loss and galvanostatic polarization measurements. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitor and with decreasing temperature. The inhibitive action of these compounds was discussed in terms of blocking the electrode surface by adsorption of the molecules. The adsorption process follows a Langmuir adsorption isotherm. The effect of temperature on the rate of corrosion in the absence and presence of these compounds was also, studied. Some activation thermodynamic parameters were calculated.

Corrosion Behavior and Its Inhibition of a Copper-Iron Alloy in Hydrochloric Acid Solution

Abstract Three pyrazole derivatives: 3(5) amino- 5(3) phenyl pyrazole (I), 3(5) amino- 5(3) [4- methyl phenyl] pyrazole (II), and 3(5) amino- 5(3) [4- methoxy phenyl] pyrazole (III) were synthesized and their corrosion inhibiting behavior for a copper-iron alloy in 1.0 M hydrochloric acid (HCl) was studied. The inhibition efficiency of these compounds was evaluated using the following techniques of measurement: weight loss, galvanostatic polarization, linear polarization, and electrochemical impedance spectroscopy. These measurements indicate these compounds have high inhibition efficiency, which increases according to the order: I < II < III. Galvanostatic polarization measurements indicated that all the investigated compounds are of the site-blocking inhibitor type. Changes in impedance parameters (charge-tranfer resistance [Rt] and double-layer capacitance [Cdl]) are indicative of the adsorption of compounds on the alloy surface, leading to the formation of a protective film. The adsorption of these in...

An interesting and efficient organic corrosion inhibitor for mild steel in acidic medium

The effect of nicotinic acid (pyridine 3-carboxylic acid) on mild steel dissolution in H2SO4 is investigated by electrochemical methods: steady state galvanostatic and potentiostatic polarisation measurements. The dissolution parameters, such as corrosion currents, passive current, flade potential, open circuit potential, cathodic and anodic Tafel slopes and inhibition efficiencies, are determined. The adsorption and corrosion rates based on heat of adsorption and activation energies are calculated from Langmuir’s adsorption isotherm. The inhibition efficiency range of 94–99% is obtained for a concentration range of 10−1 to 10−7 mol L−1. Passivating parameters revealed that these are strongly passivating additives. Synergistic effects of I— have a strong impact on the performance of these additives. These results are verified by the weight loss method. The surface analysis studies carried out by SEM supplement the galvanostatic results.

Activation of aluminium alloy sacrificial anodes by selenium

Several studies have focussed on alloying and structural modifications of aluminium alloy sacrificial anodes using different activators. The present work explores the feasibility of effective aluminium activation by selenium incorporation. The electrochemical performance of these anodes is evaluated by galvanic and galvanostatic polarization, OCP and CCP measurements etc. The selenium incorporated anode showed improved galvanic efficiency of around 70%. High performed anodes were developed by incorporating other activators of Sn and Bi along with Se in aluminium alloy anodes. The best activator combination was found to be 0.5%Se + 0.1%Sn + 0.1%Bi. This combination of activator in aluminium alloy anodes shows a galvanic efficiency of 90%.

Electrochemical Behavior of Brass in Acid Solutions and the Inhibitive Effect of Imidazole

A new voltammetric method has been proposed to determine the corrosion rates of brass in 2N HCl and H 2 SO 4 solutions with and without imidazole inhibitor in short periods of time. Significantly, it has also been possibleto determine the corrosion rates simultaneously with respect to Cu(II) and Zn(II). These results have been compared with the average corrosion rates obtained using the gravimetric (weight loss) method and some electrochemical methods like galvanostatic and potentiodynamic polarization measurements.

Studies on dissolution and inhibition of copper in nitric acid using stripping voltammetry and conductance measurement

Stripping voltammetry and conductance measurements were used for the first time to study the corrosion and inhibition of copper. The effect of nitric acid concentration, temperature and some organic compounds on the corrosion rate was studied. Regression analysis using four modes (linear, logarithmic, power and exponential) was used to correlate the results. Data obtained showed that the linear regression is the best to fit the relationship between Cu 2+ concentration–time (stripping voltammetry) and conductance–time (conductance measurements). The inhibition efficiencies of the organic substances during the active stage of copper dissolution are generally lower than in the incubation period. The increase in temperature and nitric acid concentration brought about a parallel increase in the corrosion rate. Galvanostatic polarization measurements, using simple circuit, were used to study the corrosion process of copper in nitric acid.

Oxygen nonstoichiometry and ionic transport properties of La 0.4Sr 0.6CoO 3- δ

Homogeneous samples of La 0.4Sr 0.6CoO 3- δ were obtained by the glycine nitrate process. The oxygen nonstoichiometry was determined from oxygen exchange measurements as a function of oxygen partial pressure (10 −4 bar< P O 2 <10 −2 bar) and temperature (300°C< T<900°C). The chemical diffusion coefficient D̃ was obtained from oxygen exchange measurements applying a stepwise variation of the oxygen partial pressure of the ambient atmosphere of a disk-shaped sample. The amount of oxygen absorbed or desorbed by the perovskite was analyzed as a function of time. Chemical diffusion data were evaluated using simplified and exact fitting procedures taking into account the surface exchange coefficient. Alternatively, galvanostatic polarization measurements were performed in a P O 2 -range between 10 −4 and 10 −2 bar to yield D̃ and the ionic conductivity σ i from the long time solution of the diffusion equation. Values for D̃ from polarization measurements at T=775°C and from oxygen exchange measurements at T=725°C are in good agreement with each other. D̃ and σ i increase with increasing P O 2 (10 −4 to 10 −2 bar). The ionic conductivity shows a maximum at 3- δ≈2.82 and decreases with decreasing oxygen content indicating the possible formation of vacancy ordered structures.