1‐Methyl‐3‐pyridine‐2‐yl‐thiourea as inhibitor for acid corrosion of stainless steel

The inhibiting effect of 1‐methyl‐3‐pyridine‐2‐yl‐thiourea (MPT) on the corrosion of stainless steel in 0.5 M H₂SO₄ solution was investigated using weight loss and potentiostatic polarization techniques. The percentage inhibition efficiencies and surface coverage degrees increased with increasing additive concentration. Potentiostatic polarization studies revealed that MPT is of the mixed‐type inhibitor in 0.5 M H₂SO₄ solution. The adsorption of this inhibitor is also found to obey the Langmuir adsorption isotherm. From the adsorption isotherm, value of the ΔG_ads for the adsorption process was calculated. From the corrosion rate obtained at 25–55 °C E_a, ΔH_a and possible mechanism have been proposed. Scanning electron microscopy (SEM) was done from the surface of the exposed sample indicating uniform film on the surface.     

Effect of hexamethylpararosaniline chloride (crystal violet) on mild steel corrosion in acidic media

The corrosion inhibition of mild steel in 0.5 M H₂SO₄ and 1 M HCl by hexamethylpararosaniline chloride (HMPC) was investigated using the gravimetric technique in the temperature range 303–333 K. The results indicate that HPMC inhibited the corrosion reaction in both acid media at all temperatures and inhibition efficiency increased with HMPC concentration. The inhibiting action is attributed to general adsorption of protonated and molecular HPMC species on the corroding metal surface. Adsorption followed a modified Langmuir isotherm and the Temkin isotherm, with very high negative values of the free energy of adsorption (). An increase in temperature reduced the inhibition efficiency of HPMC in 0.5 M H₂SO₄ but increased efficiency in 1 M HCl. Activation parameters such as activation energy (E_a), activation enthalpy (ΔH^∗) and activation entropy (ΔS^∗) as well as the adsorption heat (Q_ads) were evaluated from the effect of temperature on corrosion and inhibition processes.     

Polyaspartic acid as a green corrosion inhibitor for carbon steel

The inhibitor effect of the environmentally friendly corrosion inhibitor polyaspartic acid (PASP) on the corrosion of carbon steel in 0.5 M H₂SO₄ was investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Polarization curve results clearly reveal the fact that PASP is a good anode‐type inhibitor. EIS results confirm its corrosion inhibition ability. The inhibition efficiency increases with increasing PASP concentration, and the maximum inhibition efficiency was 80.33% at 10 °C. SEM reveals that a protective film forms on the surface of the inhibited sample. The adsorption of this inhibitor is found to follow the Freundlich adsorption isotherm. A mechanism is proposed to explain the inhibitory action of the corrosion inhibitor.     

Triazolyl blue tetrazolium bromide as a novel corrosion inhibitor for steel in HCl and H2SO4 solutions

The inhibition effect of triazolyl blue tetrazolium bromide (TBTB) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl and 0.5 M H₂SO₄ solution was investigated for the first time by weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS) methods. The results show that TBTB is a very good inhibitor, and is more efficiency in 1.0 M HCl than 0.5 M H₂SO₄. The adsorption of TBTB on CRS surface obeys Langmuir adsorption isotherm. Polarization curves reveal that TBTB acts as a mixed-type inhibitor in both acids.     

Water soluble conducting polymer composite of polyvinyl alcohol and leucine: An effective acid corrosion inhibitor for mild steel

A new corrosion inhibitor namely poly(vinyl alcohol‐leucine) composite (PVAL) has been synthesized and its influence on corrosion inhibition of mild steel in 1 M hydrochloric acid solution has been studied by weight loss and potentiodynamic polarization techniques. The composite (PVAL) showed more than 95% inhibition efficiency (IE) at an optimum concentration of 0.6% by weight. The inhibition efficiency of inhibitor has been found to vary with inhibitor concentration, solution temperature, and immersion time. Various kinetic and thermodynamic parameters (E_a, ΔH_o, ΔS_o for corrosion and ΔG_ads, ΔH_ads, ΔS_ads for adsorption) reveal a strong interaction between inhibitor and mild steel surface. The negative values of ΔG_ads indicate the spontaneous adsorption of the inhibitor on mild steel surface. Potentiodynamic polarization studies showed PVAL as mixed type inhibitor. It inhibits mild steel corrosion by blocking the active sites of the metal. Electrochemical impedance spectroscopic (EIS) techniques were also used to investigate the mechanism of corrosion inhibition.     

樟树叶提取液在硫酸介质中对碳钢的缓蚀作用

应用动电位极化法和电化学阻抗(EIS)研究了樟树叶提取液(CCLE)在硫酸介质中对碳钢的缓蚀性能和缓蚀机理. 结果表明, 采用酸浸泡法从樟树叶中提取的缓蚀剂, 对碳钢在10% H₂SO₄溶液中具有良好的缓蚀作用, 随着提取液浓度的增加, 缓蚀效率增大; 随着实验温度升高, 缓蚀效率减小. 樟树叶提取液为混合抑制型缓蚀剂, 提取液中的有效缓蚀成分在碳钢表面的吸附满足Langmuir等温吸附方程; 樟树叶提取液的加入使碳钢在硫酸中反应的表观活化能增加, 起到缓蚀作用.     

Adsorption Properties and Inhibition of Mild Steel Corrosion in 0.5 M H2SO4 Solution by Some Triazol Compound

The effect of 3,5-dimethylbenzoic acid [1,2,4]triazol derivative (DBTE) on the corrosion of mild steel in 0.5 M H₂SO₄ solution was evaluated in this study by means of weight loss test, EIS, potentiodynamic polarization, and SEM. The results revealed that DBTE acted as a mixed-type inhibitor without change of the mechanism of hydrogen evolution. The inhibition efficiency increased with the increase in concentration of DBTE, and the adsorption behavior of DBTE on the mild steel surface followed the Langmuir adsorption isotherm. The thermodynamic parameters reveal that the chemisorption was the dominant adsorption process, and good inhibition performances in the studied range of temperatures were observed.     

Inhibition action of tween‐80 on the corrosion of cold rolled steel in sulfuric acid

The inhibition action of a nonionic surfactant of tween‐80 on the corrosion of cold rolled steel (CRS) in sulfuric acid (H₂SO₄) has been investigated by weight loss and potentiodynamic polarization methods. Atomic force microscope (AFM) provided the CRS surface conditions. The results show that tween‐80 is a good inhibitor in 1.0 M H₂SO₄, and its adsorption obeys Langmuir adsorption isotherm. Effects of temperature (20–50 °C) and acid concentration (0.5–7.0 M) on the inhibition action were investigated. Polarization curves show that tween‐80 is a mixed‐type inhibitor in sulfuric acid, but prominently inhibits the cathodic reaction. The results obtained from weight loss and potentiodynamic polarization are consistent, and the inhibition action could also be evidenced by AFM images.     

Synergistic of a coumarin derivative with potassium iodide on the corrosion inhibition of aluminum alloy in 1.0 M H2SO4

Synergistic effects of the addition of KI on the corrosion inhibitive performance of a coumarin derivative on an aluminum alloy in 1.0 M H₂SO₄ at different temperatures were studied using various electrochemical measurements. Density functional theory was used to calculate the quantum chemical parameters of the coumarin derivative. The experimental results showed that the coumarin derivative is considered as a mixedtype inhibitor. The corrosion potential values were almost unchanged upon the addition of PBBC to the acidic solution. The inhibition efficiency increases with increasing inhibitor concentration and increases further in the presence of 6.02 mM KI but decreases significantly at higher temperature. The adsorption of PBBC obeyed the Langmuir isotherm, and being chemically adsorbed at lower temperatures, while physical adsorption is favoured at higher temperature. The theoretical results indicated that the coumarin derivative was adsorbed onto the surface of Al2024 through the sulfur, oxygen and nitrogen atoms.     

Synergistic Effect of Purpald with Tartaric Acid on the Corrosion Inhibition of Mild Steel: from Electrochemical to Theoretical Insights

The mutually corroborated electrochemical measurements and theoretical calculations were used to investigate the corrosion inhibition performances of purpald (4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, AHMT) and its synergistic effect with tartaric acid (TA) on mild steel in 0.5 M H₂SO₄ solution. The experimental results show that the inhibition efficiency increases with the concentration of AHMT and increases further when TA exists. Density functional theory (DFT) calculations were performed to interpret the measured data and trends observed in the electrochemical studies. Furthermore, molecular dynamic simulation revealed a nearly flat configuration for molecules on metal surface with negative adsorption energies in a sequence agreed with experimental observation.

     

Study of the mechanism and inhibiting efficiency of 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole on mild steel corrosion in acidic media

The efficiency of a new triazole derivative, namely, 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole (4-MTHT) has been studied for corrosion inhibition of mild steel in 1 M hydrochloric acid (HCl) and 0.5 M sulphuric acid (H₂SO₄). Corrosion inhibition was studied using electrochemical methods and weight loss measurements. These studies have shown that 4-MTHT was a very good inhibitor. 4-MTHT behaved better in 1 M HCl than in 0.5 M H₂SO₄ and inhibition efficiencies up to 99% and 80% can be obtained in 1 M HCl and 0.5 M H₂SO₄, respectively. Activation energies (E_a) in the presence and absence of 4-MTHT were obtained by measuring the temperature independence of the corrosion current. The potential of zero charge of mild steel was studied by ac impedance method, and the mechanism of adsorption has been discussed. The adsorption of 4-MTHT followed Langmuir's adsorption isotherm in both acids.     

Adsorbtion and inhibition effect of thiourea on mild steel in acidic media

The effect of thiourea on electrochemical corrosion behavior of mild steel was investigated in 0.5M HCl solution at room temperature by electrochemical impedance spectroscopy (AC Impedance) and Tafel polarization (DC Polarization) methods. The results show that thiourea act as mixed type inhibitor. The inhibition efficiency obtained from AC Impedance and DC polarization methods are in good agreement. The Nyquist plots show that the corrosion behavior of mild steel in 0.5M HCl solution in the absence and in the presence of thiourea, consist a simple capacitive loop. Changes in impedance parameters (R_ct and C_dl) are indicative of adsorption of thiourea on the metal surface, leading to the formation of protective film. Thiourea is found to adsorb on mild steel surface steel in 0.5M HCl solution, according to the Langmuir adsorption isotherm.     

2,5-Bis(4-dimethylaminophenyl)-1,3,4-oxadiazole and 2,5-bis(4-dimethylaminophenyl)-1,3,4-thiadiazole as corrosion inhibitors for mild steel in acidic media

2,5-Bis(4-dimethylaminophenyl)-1,3,4-oxadiazole (DAPO) and 2,5-bis(4-dimethylaminophenyl)-1,3,4-thiadiazole (DAPT) have been synthesised and their inhibiting action on the corrosion of mild steel in 1 M HCl and 0.5 M H₂SO₄ at 30 °C has been investigated by various corrosion monitoring techniques. At constant acid concentration, the inhibitor efficiency of both the compounds is found to increase with inhibitor concentration. DAPT is slightly more efficient in 0.5 M H₂SO₄ than in 1 M HCl whereas DAPO is more efficient in 1 M HCl. Of the two, DAPT appears to be a better inhibitor. Potentiostatic polarisation studies show that both are mixed-type inhibitors in 1 M HCl but cathodic-type in 0.5 M H₂SO₄. The inhibitors function through adsorption following Langmuir isotherm in both the acids. The electronic properties of DAPO and DAPT, obtained using the AM1 semi-empirical quantum chemical approach, have been correlated with their experimental inhibition efficiencies using the linear resistance model (LR). These inhibitors are considered as a non-cytotoxic substances.     

Corrosion behavior of mild steel in the presence of scale inhibitor in sulfuric acid solution

Surfactants such as non-ionic polyethylene glycol tert-octylphenyl ether (Triton X-114) have been studied as efficient corrosion inhibitors in acid medium. In this study inhibition performance of Triton X-114 has been evaluated as corrosion inhibitor for mild steel in 0.5 mol l⁻¹ H₂SO₄. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and linear polarization (LPR) techniques has been applied to determine the electrochemical behaviour of Triton X-114. The maximum efficiency of Triton X-114 was found as 96% at the concentration 5.0 × 10⁻⁵ mol l⁻¹. The adsorption isotherm of inhibitor on the mild steel surface was found to be in a good agreement with the Langmuir and the standard free energy value (ΔG _ads^°) was calculated as −50.1 kJ mol⁻¹, which shows that adsorption of Triton X-114 on the mild steel surface improves the inhibition characteristics in 0.5 M H₂SO₄.     

On the inhibition of mild steel corrosion by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol

The corrosion inhibition of mild steel in a 2.5 M H₂SO₄ solution by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT) was studied at different temperatures, utilising open circuit potential, potentiodynamic and impedance measurements. The results indicate that APTT performed as an excellent mixed-type inhibitor for mild steel corrosion in a 2.5 M H₂SO₄ solution and that the inhibition efficiencies increased with the inhibitor concentration but decreased proportionally with temperature. The kinetic and thermodynamic parameters for adsorption of APTT on the mild steel surface were calculated. A chemisorption mechanism of APTT molecules on the mild steel surface was proposed based on the thermodynamic adsorption parameters.     

Inhibitory effect of some amino acids on corrosion of Pb-Ca-Sn alloy in sulfuric acid solution

The present article describes the inhibition effect of amino acids cysteine (Cys), methionine (Met) and alanine (Ala), towards the corrosion of lead-alloy (Pb-Ca-Sn) in H₂SO₄ solution by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), weight loss measurement and scanning electron microscopy (SEM) methods. The influence of inhibitor concentration, temperature and time on inhibitory behavior of the amino acids was investigated. The corrosion data including corrosion current density (I_corr), corrosion potential (E_corr) and charge transfer resistance (R_ct) were determined from Tafel plots and EIS. Recording impedance spectra showed that the charge transfer resistance is increased by increasing adsorption time. The SEM micrographs revealed that the corroded surface area is decreased in the presence of amino acids. Meanwhile, the inhibition efficiency (IE) was found to be depending on the type of amino acid and its concentration. The IE for 0.1 M Cys in 0.5 M H₂SO₄ is greater than 96%. Adsorption isotherms were fitted by Langmuir isotherm.     

Corrosion Protection Properties of 4-[(E)-[(2,4-Dihydroxy phenyl)methylidene] amino]-6-methyl-3-sulfanylidene-2,3,4,5-tetrahydro-1,2,4-triazin-5-one [DMSTT] Toward Mild Steel in Sulfuric Acid

The inhibition of mild steel corrosion in aerated 0.5 N H₂SO₄ solution was investigated using potentiodynamic polarization studies (Tafel), linear polarization studies, electrochemical impedance spectroscopy studies, adsorption studies, and surface morphological studies. The effect of inhibitor concentration on corrosion rate, the effect of temperature, degree of surface coverage, adsorption kinetics, and surface morphology are investigated. The inhibition efficiency increased markedly with increase in the additive concentration and decreased slightly with increasing temperature. The presence of DMSTT decrease the double-layer capacitance and increase the charge transfer resistance. The value of activation energy (E _a) of metal corrosion, adsorption equilibrium constant (K _ads), and free energy of adsorption (ΔG _ads) were calculated from the temperature dependence of corrosion current. The adsorption of inhibitor molecule on mild steel surface follow Langmuir isotherm. DMSTT offers excellent inhibition properties and acts as a mixed-type inhibitor.     

Shot Noise Analysis to Investigate the Corrosion Inhibition of AZ91D Magnesium Alloy in Sulfuric Acid Solution

The corrosion inhibition of AZ91D magnesium alloy in 0.01 M H₂SO₄ by a Schiff base compound was investigated using Potentiodynamic polarization, Electrochemical Impedance Spectroscopy and Electrochemical Noise methods. It is found that the Schiff base acts as mixed-type inhibitor and the inhibition efficiency increases with concentration. Electrochemical impedance spectroscopy results showed that the Schiff base acts by adsorption at the metal/solution interface. Shot noise analysis showed that the inhibitor addition decreases the number of charge transfer events instead of the value of charge transfer at each electrochemical corrosion event. The corrosion inhibition effect was approved by suitable surface analysis.     

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 H₂SO₄ 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 H₂SO₄ 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 H₂SO₄. IR and SEM investigations also confirmed the adsorption of BuTPPB on the mild steel surface in 0.5 M H₂SO₄ solutions. The molecular parameters obtained using PM3 semi-empirical method, were correlated with the experimentally measured inhibitor efficiencies.     

Inhibitive properties, thermodynamic and quantum chemical studies of alloxazine on mild steel corrosion in H2SO4

Alloxazine (ALLOX) was tested as corrosion inhibitor for mild steel in 0.5 M H₂SO₄ solution using non-electrochemical technique (gravimetric and UV–Visible spectrophotometric measurements) at 303–333 K. ALLOX acts as inhibitor for mild steel in acidic medium. Inhibition efficiency increases with increase in concentration of ALLOX but decrease with rise in temperature. The adsorption of ALLOX was found to follow Temkin adsorption isotherm model. Both the activation and thermodynamic parameters governing the adsorption process were calculated and discussed. The adsorption follows a first-order kinetics. DFT study gave further insight into the mechanism of inhibition action of ALLOX.