The effect of temperature and concentration on the corrosion inhibition mechanism of an amphiphilic amido-amine in CO2 saturated solution

The corrosion inhibition mechanism of the N-[2-[(2-aminoethyl)amino]ethyl]-9-octadecenamide on mild steel surface in CO₂-saturated 5% NaCl solution has been studied. The inhibition efficiency decreases with increasing temperature. Adsorption of the inhibitor studied is found to follow the Frumkin adsorption isotherm. EIS results show that the mechanism of its corrosion inhibition at concentrations higher than critical micelle concentration is by forming a protective porous bi-layer. The activation energy, thermodynamic parameters and electrochemical results reveal a change in the adsorption mode of the inhibitor studied: the inhibitor could primarily be physically adsorbed at low concentrations, while chemisorption is favoured as concentration increases.     

The Inhibition Effect of Synthesized 4-Hydroxybenzaldehyde-1,3propandiamine on the Corrosion of Mild Steel in 1 M HCl

The corrosion inhibition of mild steel in 1 M HCl by 4-hydroxybenzaldehyde-1,3propandiamine (4-HBP) has been investigated using potentiodynamic polarization, electrochemical impedance spectroscopy and chronoamperometry measurements. The experimental results suggest that this compound is an excellent corrosion inhibitor for mild steel and the inhibition efficiency increases with the increase in inhibitor concentration. Polarization curves reveal that this organic compound is a mixed-type inhibitor. The effect of temperature on the corrosion behavior of mild steel in 1 M HCl with the addition of the Schiff base was studied in the temperature range from 25 to 65 °C. The experimentally obtained adsorption isotherms follow the Langmuir equation. Activation parameters and thermodynamic adsorption parameters of the corrosion process such as E _a, ΔH, ΔS, K _ads, and ΔG _ads were calculated by the obtained corrosion currents at different temperatures and using the adsorption isotherm. The morphology of mild steel surface after its exposure to 1 M HCl solution in the absence and in the presence of 4-HBP was examined by AFM images.     

硫酸介质中丙氨酸复合缓蚀剂的研究

目的研究丙氨酸和碘化钾共同存在于硫酸溶液中,对碳钢的协同缓蚀作用。方法采用极化曲线、交流阻抗谱、扫描电镜、X射线光电子能谱(XPS)以及El-Awady动力学模型,对丙氨酸、丙氨酸与碘化钾复配缓蚀剂对碳钢在硫酸介质中的缓蚀性能和吸附机理进行探究。结果在10%的硫酸体系中,对碳钢的缓蚀性能随着缓蚀剂浓度增大而增强。单独使用丙氨酸作为缓蚀剂,丙氨酸分子在碳钢表面呈单分子层吸附,缓蚀效率最高仅达到29%,缓蚀效果不明显。经过丙氨酸与碘化钾复配后,缓蚀效果显著提高,当丙氨酸质量浓度为300 mg/L,碘化钾质量浓度为250 mg/L时,缓蚀效率达到92%以上。XPS谱图表明,缓蚀剂主要是通过分子中的N原子与碳钢表面Fe原子形成共价键,吸附在碳钢的表面,与KI复配后,I-吸附在碳钢表面,并部分氧化,形成I_3~-。El-Awady动力学模型研究说明该复配缓蚀剂为混合型缓蚀剂,且在碳钢表面自发形成多分子层吸附膜。结论在10%的硫酸溶液中,丙氨酸分子通过物理吸附或化学吸附作用,吸附在碳钢表面,减缓腐蚀反应发生。碘化钾添加后,发挥连接缓蚀剂分子和碳钢表面的桥梁作用,从而协助丙氨酸吸附到碳钢表面,提高丙氨酸在碳钢表面的覆盖率,在提高缓蚀效率的同时,减少了丙氨酸的使用量,有效地抑制了钢材的腐蚀。     

Zum Verhalten von Natriumsilikat als Korrosionsinhibitor für Aluminium in alkalischen Lösungen

The behaviour of sodium silicate as a corrosion inhibitor for aluminium in alkaline solutions Even at a temperature of 80°C and even in the presence of intensive mechanical stresses on the metal by a sharp spray jet (with a spraying pressure of 30 atmospheres excess pressure at the nozzle), sodium silicate (Na₂O:SiO₂ = 1 : 2,5) is able to prevent corrosion of pure aluminium (99,5 pC) by alkaline solutions (pH 11). For this purpose, very small quantities of adsorbed silicate per unit of area are already sufficient. It is essential, however, that the SiO₂ concentration in the solution does not sink below a certain minimum value, depending on ambient conditions, so that a sufficient quantity of silicate can be adsorbed. With increasing temperatures and spraying pressures, the silicate concentration must be higher if effective corrosion protection is to be attained. The corrosion-preventing film on the metal surface is formed by non-aggregated silicate. Different metals draw different quantities of corrosion inhibitor from the silicate solutions. This behaviour is presumably governed not only by the specific adsorption capacity for silicate ions but also by the corrosion resistance of the different metals in the solution.     

The synergistic inhibitive effect and some quantum chemical parameters of 2,3-diaminonaphthalene and iodide ions on the hydrochloric acid corrosion of aluminium

The effect of iodide ions on the inhibitive performance of 2,3-diaminonaphthalene (2,3-DAN) in 1 M HCl for aluminium corrosion has been studied using hydrogen evolution (gasometry) measurements at 30 and 40 °C. Results obtained showed that the presence of 2,3-DAN molecules in the corrosive medium (1 M HCl solution) inhibits the corrosion process of aluminium and as the concentration of 2,3-DAN increases the inhibition efficiency also increased at the studied temperatures. A synergistic effect was observed between KI and 2,3-DAN. The experimental results suggest that the presence of iodide ions in the solutions stabilized the adsorption of 2,3-DAN molecules on the metal surfaces and, therefore improve the inhibition efficiency of 2,3-DAN. Phenomenon of physical adsorption is proposed for the inhibition and the process followed the Freundlich adsorption isotherm. The activation energy (E_a), heat of adsorption (Q_ads) and free energy of adsorption for the corrosion process (ΔG_ads) have been evaluated at the different temperatures and the values support the results obtained. Some quantum chemical parameters and the Mulliken charge densities for 2,3-diaminonaphthalene were calculated by the AM1 Semi-empirical method to provide further insight into the mechanism of inhibition of the corrosion process.     

Aminopyrimidine derivatives as inhibitors for corrosion of 1018 carbon steel in nitric acid solution

The effect of some aminopyrimidine derivatives on the corrosion of 1018 carbon steel in 0.05 M HNO₃ solution was studied using weight loss and polarization techniques. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitor and with decreasing temperature. The addition of KI to aminopyrimidine derivatives enhanced the inhibition efficiency due to synergistic effect. The inhibitors are adsorbed on the steel surface according to Temkin isotherm. Some thermodynamic functions were computed and discussed. It was found that the aminopyrimidine derivatives provide a good protection to steel against pitting corrosion in chloride containing solutions.     

Studies on the Inhibition of Mild Steel Corrosion by Rauvolfia serpentina in Acid Media

Alkaloid extract of Rauvolfia serpentina was tested as corrosion inhibitor for mild steel in 1 M HCl and H₂SO₄ using weight loss method at three different temperatures, viz., 303, 313, and 323 K, potentiodynamic polarization, electrochemical impedance spectroscopy and scanning electron microscope (SEM) studies. It is evident from the results of this study that R. serpentina effectively inhibits the corrosion in both the acids through adsorption process following Tempkin adsorption isotherm. The protection efficiency increased with increase in inhibitor concentration and temperature. Free energy of adsorption calculated from the temperature studies also revealed the chemisorption. The mixed mode of action exhibited by the inhibitor was confirmed by the polarization studies while SEM analysis substantiated the formation of protective layer over the mild steel surface.     

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.     

High-temperature inhibitor of steel corrosion in sulfuric acid solutions

A new high-temperature (up to 140°C) inhibitor of steel corrosion in sulfuric acid, IFKhAN-92, that yields Z = 99% at a content of at least 1 wt % was developed. To enhance the protective effect of IFKhAN-92 at an elevated temperature, KI additions may be used. IFKhAN-92 was shown to be effective in hindering electrode reactions on steel. The high efficiency of this catalyst in H₂SO₄ solutions is most likely conditioned by the specific adsorption of IFKhAN-92 molecules on a metal surface.     

Corrosion and corrosion control of mild steel in concentrated H2SO4 solutions by a newly synthesized glycine derivative

A newly synthesized glycine derivative (GlyD1), 2-(4-(dimethylamino)benzylamino)acetic acid hydrochloride, was used to control mild steel corrosion in 4.0 M H₂SO₄ solutions at different temperatures (278–338 K). Tafel extrapolation, linear polarization resistance (LPR) and impedance methods were used to test corrosion inhibitor efficiency. An independent method of chemical analysis, namely ICP-AES (inductively coupled plasma atomic emission spectrometry) was also used to test validity of corrosion rate measured by Tafel extrapolation method. Results obtained were compared with an available glycine derivative (GlyD2) and glycine (Gly). Tafel polarization measurements revealed that the three tested inhibitors function as mixed-type compounds. The inhibition efficiency increased with increase in inhibitor concentration and decreased with temperature, suggesting the occurrence of physical adsorption. The adsorptive behaviour of the three inhibitors followed Temkin-type isotherm and the standard free energy changes of adsorption () were evaluated for the three tested inhibitors as a function of temperature. The inhibition performance of GlyD1 was much better than those of GlyD2 and Gly itself. Results obtained from the different corrosion evaluation techniques were in good agreement.     

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.     

Experimental investigation on corrosion inhibition of thiourea on aluminum surface in 0.5 M H2SO4 acid solution

Effect of thiourea on corrosion resistance of aluminum in 0.5 M H₂SO₄ solution is experimentally investigated. Results show that the addition of thiourea inhibits the sulfuric acid corrosion of aluminum. The inhibition efficiency can be enhanced with an increase in thiourea concentration. It is found that Rp values increases and C _dl values decreases with increasing inhibitor concentration. The inhibition happens through adsorption of thiourea on the metal surface without modifying the mechanism of corrosion process. Inhibition efficiency obtained from all methods is in good agreement. The adsorption of inhibitor on aluminum surface from 0.5 M H₂SO₄ acid solution obeys Langmuir adsorption isotherm.

     

A comparative study of the corrosion inhibition of mild steel in sulphuric acid by 4,4-dimethyloxazolidine-2-thione

The corrosion protection of mild steel in a 2.5 M H₂SO₄ solution by 4,4-dimethyloxazolidine-2-thione (DMT) was studied at different temperatures by measuring changes in open circuit potential (OCP), potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Corrosion current densities calculated from EIS data were comparable to those obtained from polarisation measurements. Results showed that DMT inhibited mild steel corrosion in a 2.5 M H₂SO₄ solution and indicated that the inhibition efficiencies increased with the concentration of inhibitor, but decreased proportionally with temperature. Polarisation curves showed that DMT is a mixed-type inhibitor. Changes in impedance parameters suggested the adsorption of DMT on the mild steel surface, leading to the formation of protective films. The DMT adsorption on the mild steel surface followed the Langmuir adsorption isotherm. The kinetic and thermodynamic parameters for dissolution and adsorption were investigated. Comprehensive adsorption (physisorption and chemisorption) of the inhibitor molecules on the mild steel surface was suggested based on the thermodynamic adsorption parameters.     

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.     

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.     

British Joint Corrosion Group Report of the Executive Committee

Abstract

The corrosion of pure iron in neutral aqueous solutions in the presence of some guanidine derivatives such as dicyandiamide, guanylurea and biguanide has been studied at different temperatures. The low corrosion rates were specially chosen in order to study the behaviour of the adsorbed additive layer – whether catalytic or inhibitive. The inhibition of the corrosion of pure iron by biguanide has been shown to follow the Langmuir adsorption isotherm over a wide concentration range and the activation energies to decrease with increasing biguanide concentration. The adsorbed molecules of dicyandiamide and guanylurea, however, behave as catalysts towards the hydrogen discharge reaction, although dicyandiamide, like biguanide, is found to be an endothermic adsorbing species and the effective inhibition increases with increasing temperature. It has been concluded that, for the adsorption type of inhibitors, the observed corrosion rate is the sum of the corrosion rates of the uncovered suiface and of the surface covered by the adsorbing species. Some adsorbing inhibitors like biguanide, effectively protect the metal suiface from corrosion showing that the contribution of the latter rate becomes negligibly small or zero.     

Eco-friendly corrosion inhibitors: Synergistic effect of ethanol extracts of calotropis for corrosion of mild steel in acid media using mass loss and thermometric technique at different temperatures

The inhibitive action of leaves (LV), Latex (LX) and Fruit (FT) extracts of Calotrpis procera and Calotropis gigantea on mild steel corrosion in HCl, H₂SO₄ and mixture of solutions have been studied using mass loss and thermometric technique at different temperatures. The results indicate that the ethanolic extracts functioned as a good corrosion inhibitor in both environments and inhibition efficiency increased with extracts concentration. A mechanism of chemical adsorption of the plants components on the surface of the metal is proposed for the inhibition behavior. The inhibition efficiency increases up to 86.37%.     

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.     

Synergistic inhibition behaviour of methylbenzyl quaternary imidazoline derivative and iodide ions on mild steel in H2SO4 solutions

The inhibition behaviour of 2-undecyl-1-ethylamino-1-methylbenzyl quaternary imidazoline (2UMQI) and KI on mild steel in 1.0 M H₂SO₄ solutions was investigated at 25 °C using electrochemical methods. The results indicated that 2UMQI inhibited the corrosion of mild steel and the extent of inhibition increased with 2UMQI concentrations. The inhibition action in the presence of 2UMQI is due to physical adsorption of 2UMQI. A mixed-inhibition mechanism is proposed for the inhibitive effects of 2UMQI. Inhibition efficiency of 2UMQI was enhanced by the addition of iodide ions. In the presence of KI, the potentials of unpolarization, E_u was observed and increased with KI concentration.     

Effect of temperature on copper corrosion in high-level nuclear waste environment

The effect of temperature on the corrosion behavior of copper in simulated high-level nuclear waste environment was systematically studied. Electrochemical methods, including electrochemical impendence spectra, Mott–Schottky technology, cyclic polarization, and potentiostatic polarization, were employed to characterize the corrosion behavior of copper at different temperatures. Stereoscopic microscopy and scanning electron microscopy were used to examine the surface morphology, and X-ray photoelectron spectroscopy analysis was used to identify the composition of the passive film. The experimental results show that corrosion resistance of the passive film does not blindly decrease with the increase of temperature but increases at 60 °C owing to a compact outer layer; there is a potential for pitting corrosion, which decreases as the temperature increases. The main product of copper in an anaerobic aqueous sulfide solution is Cu₂S but the content of CuS increases at higher temperatures. The whole passivation range shows p-type semiconductor characteristics and the magnitude of the acceptor density is 10²³ cm^?3, which increases with increasing temperature.