Corrosion inhibition of steel by hydrazine

The corrosion inhibition of steel in a closed system containing hydrazine at room temperature has been established. The steady-state potential measurements as well as weight loss measurements agree in indicating that hydrazine was found to behave in a similar manner to anodic inhibitors. A sharp ennoblement of potential occurs at concentration of 10^?2M accompanied by complete protection. The mechanism of inhibition by hydrazine is assumed to be due to its preferential adsorption on the local anodes inducing anodic polarization. After a certain critical concentration of hydrazine is reached complete blocking of the pores occurs which causes complete inhibition. For hydrazine-sulphate or hydrazine-chloride mixtures, a linear relationship is found between log hydrazine concentration and log maximum tolerated concentration of the aggressive ion. For hydrazine-sulphide mixtures, a concentration of 5 × 10^?2M hydrazine could tolerate a wide range of concentrations of sulphide ions.     

Fluoride induced corrosion of steel rebars in contact with alkaline solutions, cement slurry and concrete mortars

Corrosion behaviour of mild steel rebars has been studied in contact with 0.01 N NaOH, saturated lime water, cement slurry and embedded mortars having different concentrations of fluoride ions. Weight-loss, electrochemical DC cyclic polarisation and polarisation resistance, surface topographic and X-ray diffraction (XRD) techniques have been used to investigate the effects of fluoride ion on the corrosion behaviour of the material. Under all the conditions of the exposure it is observed that a low content of fluoride (?25 ppm) in the corrodent has deleterious action on the performance of the steel, where as at its higher content (?100 ppm) the ion has rather an inhibiting effect on corrosion rate. XRD studies of the corrosion product accumulated on the steel surface in the presence of fluoride ion indicate the predominance of magnetite oxide phase. Accelerating effect of the ion is observed to be due to depolarisation of cathodic reaction of the corrosion process. Observations show that in accelerating range of fluoride (?25 ppm) it has almost double corrosive effect than noted for equal concentration of chloride ion.     

The effect of stress on the corrosion behaviour of mild steel in alkaline solutions

The influence of stress, type of aggressive anion and anodic current density on the corrosion behaviour of mild steel in lime water has been studied. Under open circuit condition the passivity of steel in lime water containing low concentrations of C1?, SO₄^2? or S^2? ions was impaired by the application of stress. In the presence of high concentrations of these ions corrosion was enhanced by the application of stress. Sulphide ions were found to be more dangerous than C1- or SO₄^2? ions at the free corrosion potential. With anodic polarization, S^2? ions are inhibitive both in the absence and in presence of stress. In early stages at low current densities, the anodic process was stimulated by the application of stress.     

Azoles as corrosion inhibitors for mild steel in alkaline mine water

The corrosion of mild steel in alkaline mine water containing various concentrations of benzotriazole, benzimidazole and imidazole has been studied by weight loss and polarization techniques at 303 K. These azoles inhibit corrosion effectively even in trace concentrations. The degree of corrosion inhibition is a function of temperature, concentration and nature of the inhibitor. The corrosion inhibition is explained by considering the adsorption and/or complex formation by the inhibitors on the corroding mild steel surface. Thermodynamic parameters for adsorption are calculated using the Frumkin adsorption isotherm. The inhibitors acted as anodic inhibitors.     

Comparative Study of Factors Influencing the Action of Corrosion Inhibitors for Mild Steel in Neutral Solution: III. Sodium Nitrite

Abstract

The action of sodium nitrite as a corrosion inhibitor for mild steel in neutral aqueous solution has been studied in relation to the surface preparation of the steel, the presence of aggressive salts in the solution, and temperature.

Surface preparation of mild steel has little effect on the minimum concentration of nitrite required for protection in distilled water. In solutions containing aggressive anions a linear relation exists between the logarithm of the nitrite concentration and the logarithm of the maximum concentration of aggressive anion that will permit inhibition. In solutions of low nitrite concentration the order of aggressiveness of anions is sulphate > chloride > nitrate; the order changes with increase in nitrite concentration. Corrosion in non-inhibiting nitrite/aggressive anion solutions is frequently of a severely localised form. A 5-fold increase in nitrite requirement for inhibition of abraded mild steel in distilled water is found between 5° and 70°, with a further large, rather indeterminate, increase above 70°.

Of the three inhibitors studied in Parts I-III, chromate and nitrite are slightly moreeffective than benzoate for the protection of an abraded surface, and considerably more so for a grit-blasted surface. In general, nitrite is the most tolerant towards the presence of chloride, but it is the most dangerous if excess chloride is present. The increase in inhibitor requirement with increase in temperature from 5° to 70° is very approximately the same for all three inhibitors, that is, about 5– to 10–fold,with all inhibitors needing much higher concentrations at about 90°.     

Comparative Study of Factors Influencing the Action of Corrosion Inhmitors for Mild Steel in Neutral Solution: II. Potassium Chromate

Abstract

The action of potassium chromate as a corrosion inhibitor for mild steel in neutral aqueous solution has been studied in relation to the surface preparation of the steel, the presence of aggressive salts in the solution, and temperature.

Surface preparation of mild steel has little effect on the minimum concentration of chromate required for protection in distilled water. In solutions containing aggressive anions a linear relation exists between the logarithm of the chromate concentration and the logarithm of the maximum concentration of aggressive anion that will permit inhibition. In solutions of low chromate concentration, up to 10^?1M, the order of aggressiveness of anions is chloride > sulphate > nitrate; the order changes at chromate concentration above 10^?1M to chloride > nitrate > sulphate. Corrosion in non-inhibiting chromate/aggressive anion solutions is always of a localised nature but is usually stifled, thus not leading to ‘dangerous’ attack. A 5-fold increase in chromate requirement for inhibition of abraded mild steel in distilled water is found between 5° and 60°, with a further large, rather indeterminate, increase above 60°.     

3,5-二溴水杨醛-2-噻吩甲酰肼席夫碱缓蚀剂在油田水中对碳钢的缓蚀性能及分子动力学模拟

合成了一种新的席夫碱缓蚀剂3,5-二溴水杨醛-2-噻吩甲酰肼(L2),通过Tefel极化曲线、电化学阻抗、扫描电镜和分子动力学模拟方法研究了该缓蚀剂在模拟油田水中对碳钢的缓蚀效果,并探讨了其缓蚀机理和吸附行为。结果表明,L2在不同温度、H2S浓度、pH值和Cl-浓度条件下的模拟油田水中对碳钢均具有良好的缓蚀性能。分子动力学模拟结果表明,在水溶液中缓蚀剂L2分子可以稳定地平行吸附在金属表面,有效地将金属表面和水分子隔开,从而起到缓蚀作用,吸附方式为多位点化学吸附;同时L2形成的分子吸附膜可有效地抑制腐蚀离子(Cl-和H3O+)在吸附膜中的扩散,避免了金属表面与腐蚀介质接触而发生腐蚀,从而表现出良好的缓蚀性能。     

Estimate of contributions of polysulfide film and inhibitor to the protection of steel from hydrogen-sulfide corrosion

A method for estimating the contributions of film formed on a corrosive surface in aggressive medium favoring its formation and INKORGAS-T30 inhibitor at the inhibition of corrosion in steel has been proposed. Experimental results obtained by studying the behavior of the St3 carbon steel in mineralized chloride medium (5 wt % NaCl) containing 50–400 mg/l H₂S and the addition of an inhibitor have been presented. Using the polarization resistance method, the protective efficacy of oxide and polysulfide surface films and an inhibitor has been estimated as a function of the duration of the action of the aggressive medium, hydrogen sulfide concentration, and the corrosion inhibitor.     

Effect of temperature and fluid velocity on corrosion mechanism of low carbon steel in presence of 2-hydrazino-4,7-dimethylbenzothiazole in industrial water medium

The corrosion inhibition of 2-hydrazino-4,7-dimethylbenzothiazole on low carbon steel in industrial water has been investigated at different temperatures and fluid velocities at different concentrations of the inhibitor using mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The results showed that corrosion resistance increased by increasing the inhibitor concentration. Optimization of the three variables has been made and correlating the results obtained using Box–Wilson statistical method. The adsorption process on low carbon steel surface obeys Flory–Huggins isotherm. The values of ΔG_ads obtained suggest that, the adsorption process of 2-HMBT on low carbon steel is chemisorption. The activation energy increased with increasing the concentration of inhibitors leading to decrease of the pre-exponential factor, and the entropy of activation increased negatively in the presence of inhibitor. SEM was used to identify the film formed on the metal surface.     

Inhibition effect of 4-phenylthiazole derivatives on corrosion of 304L stainless steel in HCl solution

Some 4-phenylthiazole derivatives were tested as corrosion inhibitors for 304L stainless steel in 3.0 M HCl using weight loss and galvanostatic techniques. The results showed that the inhibition efficiency increases with increasing the concentration of the 4-phenylthiazole derivatives. Polarization measurements showed that these derivatives act as mixed-type inhibitors. The adsorption of these inhibitors on the surface of stainless steel follows Temkin’s adsorption isotherm and kinetic model. The effect of temperature on the corrosion was investigated by the weight loss method and some thermodynamic parameters were calculated. The synergistic influence caused by thiocyanate ion on the inhibition of corrosion of 304L stainless steel in 3.0 M HCl in the presence of 4-phenylthiazole derivatives has been studied using weight loss method. The inhibition action of these 4-phenylthiazole derivatives was discussed in terms of its adsorption on the metal surface.     

The inhibition effect of the new Schiff base,namely 2,2′‐[bis‐N(4‐choloro benzaldimin)]‐1,1′‐dithio against mild steel corrosion

2,2′‐[bis‐N(4‐choloro benzaldimin)]‐1,1′‐dithio has been synthesized and its inhibiting action on the corrosion of mild steel in 0.5 M sulfuric acid was investigated by various corrosion monitoring techniques, such as weight loss and potentiodynamic polarization techniques. The experimental results suggest that this compound is a good corrosion inhibitor for mild steel and the inhibition efficiency increases with the increase in inhibitor concentration. This organic compound is a mixed type inhibitor in the acid solution, and its adsorption on the mild steel surface is also found to obey the Langmuir adsorption isotherm.     

Corrosion inhibition behaviour of thiourea derivatives in acid media against mild steel deterioration: An overview

This paper summarizes the inhibitor activity of various reported thiourea derivatives in acid media used against the deterioration of mild steel. Acid solutions have been extensively employed in manufacturing and many industrial processes for pickling and removal of undesirable scale. Mild steel is highly susceptible to corrosion in such aggressive acid media. The additives such as inhibitors are widely employed in those cases to reduce the extent of corrosion as much as possible. The survey of literature on organic inhibitors clearly indicates the potential usage of thiourea derivatives as inhibitors of mild steel corrosion. The influence of physical-chemical properties on the inhibition activity of thiourea derivatives has been discussed. This information is highly useful for different industrial applications where good performing inhibitors are being required for protecting mild steel from aggressive acid media.     

三聚氰胺对碳钢在 HCl 介质中的缓蚀作用

目的了解在HCl介质中,三聚氰胺对碳钢的缓蚀作用和缓蚀机理。方法在1 mol/L HCl溶液中添加不同浓度的三聚氰胺,测试碳钢在溶液中的动电位极化曲线和电化学阻抗谱,获得电化学参数和缓蚀效率。再结合量子化学计算结果,分析其缓蚀机理。结果针对碳钢在1 mol/L HCl溶液中的腐蚀,三聚氰胺是一种混合抑制型缓蚀剂,随其浓度的增加,缓蚀效率增大。三聚氰胺通过分子中Mulliken电荷相对较负的氮原子吸附在碳钢表面起到缓蚀作用,吸附过程为自发过程,以物理吸附为主,且符合Langmuir吸附等温方程。结论在HCl介质中,三聚氰胺对碳钢具有一定的缓蚀作用。     

电化学法研究芭蕉叶提取物在盐酸中对碳钢的缓蚀作用

目的研究芭蕉叶提取物(MBLE)在酸性环境中对碳钢腐蚀的抑制行为。方法通过热水浸提法获取MBLE,采用电化学方法研究在不同实验温度和不同浓度下MBLE在1 mol/L盐酸溶液中对碳钢的缓蚀行为,并用扫描电镜(SEM)研究金属表面腐蚀形貌。结果极化曲线研究表明,MBLE对碳钢在1mol/L盐酸中的腐蚀有明显抑制作用,属阴极抑制为主的混合型缓蚀剂;其缓蚀性能随质量浓度增大而增强,25℃时160 mg/L的MBLE缓蚀效率达到94.7%。电化学阻抗图谱研究表明,随着MBLE质量浓度的增大,碳钢表面腐蚀反应的电荷转移电阻逐渐增大,腐蚀反应抑制程度增强。变温试验研究表明,MBLE在实验温度范围内具有较好的稳定性。当MBLE质量浓度为160 mg/L时,温度从25℃增加到40℃,两种电化学方法所得缓蚀效率的变化幅度均在3%以内。MBLE缓蚀剂分子在碳钢表面的吸附服从Dhar-Flory-Huggins等温吸附式,并且属于物理和化学混合吸附。SEM研究表明,盐酸介质中MBLE可有效地抑制碳钢的腐蚀。结论对碳钢在盐酸介质中的腐蚀,MBLE是有效的绿色缓蚀剂。     

Sodium gluconate as corrosion and scale inhibitor of ordinary steel in simulated cooling water

The effect of sodium gluconate anion (SG) on the corrosion and scale inhibition of ordinary steel in simulated cooling water has been studied using weight loss, polarisation curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques. SG was studied in concentration from 10⁻⁴ M to 10⁻¹ M. Results obtained reveal that SG perform excellently as corrosion and scaling inhibitor for ordinary steel in simulated cooling water. An increase of SG concentration leads to the increase of the corrosion potential towards the positive direction. The inhibition efficiency was a low temperature dependence. The inhibitor mechanism was treated as an adsorption process according to Langmuir adsorption isotherm. The SEM/EDAX data show that was a corrosion and scale inhibitor.     

Molecular modeling of corrosion processes: development and engineering applications

Abstract

The effect of two polyacrylate based polyelectrolytes, one cationic, the other anionic, on the corrosion of mild steel in aqueous solutions has been examined. It is shown that under conditions where they accelerate corrosion the effect arises from different properties of the compounds in each case. The cationic polymer is a mild oxidising agent and, in alkaline solution, is aggressive to passive films producing localised attack. The anionic compound acts as an anodic stimulator in neutral and alkaline solutions possibly by virtue of its ability to form a complex ion with the emerging cation. Both compounds therefore accelerate corrosion in neutral and alkaline solutions. By contrast, the anionic polyelectrolyte is a mild mixed inhibitor in acid solutions. It is suggested that not all soluble polymers will adversely affect the corrosion of mild steel and that by redesign of the molecule it might be possible for polyectrolytes generally to act as both water treatment chemicals and corrosion inhibitors.     

Effect of ascorbic acid on the pitting resistance of 316L stainless steel in synthetic tap water

This study examined the effect of L-ascorbic acid (A.A) concentration on the pitting corrosion properties of 316L stainless steel (316L STS) of heat exchanger in synthetic tap water containing 400 ppm of Cl- ion. The pitting corrosion of 316L STS can be effectively inhibited by the 10^-4 M of A.A concentration. In this condition, the adsorption of A.A reinforced the passive film of steel by blocking the Cl^- ions at the active site. However, the passive film was deteriorated and severe pitting corrosion occurred above the 10^-4 M of A.A concentration. Above the 10^-4 M of A.A concentration, A.A generates soluble chelate rather than absorbs on the steel surface and it causes passive film deterioration and severe pitting corrosion. The critical ratio, which is a critical ratio of surface coverage of aggressive to inhibitive ion necessary to initiate localized corrosion, calculated 2.93 up to the 10^-4 M. It has approximately 2.93:1 ratio of the coverage of local Cl^- ions to A.A. Above the critical ratio, the pitting corrosion will occur with degradation of the passive film. On the other hands, above the 10^-4 M A.A concentration caused a negative effect because the heat energy for adsorption is increased.     

Reactivity of polyester aliphatic amine surfactants as corrosion inhibitors for carbon steel in formation water (deep well water)

Effect of different concentrations, 40-200 ppm, of various polyester aliphatic amine surfactants on inhibition of the corrosion of carbon steel in the formation water (deep well water) was investigated. These surfactants exhibit different levels of inhibition particularly at high concentration (200 ppm). Inhibition efficiencies in the range 86-96% were determined by weight loss method. Comparable results were obtained from electrochemical measurements using Tafel extrapolation and polarisation resistance methods. It was shown that all the investigated surfactants act primarily as anodic inhibitors; however, they also affect the rate and mechanism of the cathodic reaction. These compounds function via adsorption on reactive sites on the corroding surface reducing the corrosion rate of the metal. It was revealed that the adsorption of these surfactants obey Langmuir adsorption isotherm. The inhibition effectiveness increases with the length of the aliphatic hydrocarbon chain, being a maximum in the presence of surfactant IV (∼96% efficiency). The corrosion inhibition feature of this compound is attributed to the presence of a long hydrocarbon chain that ensures large surface coverage as well as the presence of multiple active centers for adsorption. Scanning electron microscopy, SEM, has been applied to identify the surface morphology of carbon steel alloy in the absence and presence of the inhibitor molecules.     

氧氯协同对304L不锈钢在高温高压硼锂水中应力腐蚀开裂的影响

采用高温高压慢应变速率拉伸试验方法(SSRT),研究了饱和氧环境下不同氯离子浓度对304 L不锈钢在高温高压硼锂水介质中氯致应力腐蚀开裂的影响。结果表明:在一定浓度范围内有氧无氯或者有氯无氧环境下,304L不发生应力腐蚀开裂。在空气饱和氧条件下,氯离子浓度在1 mg/L至10 mg/L之间变化时,应力腐蚀敏感性随浓度变化不大;而当氯离子浓度大于20 mg/L时,应力腐蚀敏感性随浓度的增加变化很大,当氯离子浓度为50 mg/L,304L几乎完全为脆性断裂。     

ATA及其与PASP复配在3.5%NaCl溶液中对碳钢的缓蚀作用

为寻找新的缓蚀荆来解决碳钢的腐蚀问题,采用极化曲线和交流阻抗方法,研究了3-氨基-1,2,4-三氮唑(ATA)及其与聚天冬氨酸(PASP)复配在3.5%NaCl溶液中对碳钢的缓蚀作用,并对比观察了碳钢在未加和加入复配缓蚀荆的3.5%NaCl溶液中浸泡后的腐蚀形貌.结果表明:ATA在3.5%NaCl溶液中对碳钢具有缓蚀作用,属阳极型缓蚀剂,其添加量以25 mg/L为最好,此时的缓蚀效果最佳,缓蚀率可达93.51%;ATA和PASP复配在3.5%NaCl溶液中对碳钢具有缓蚀协同作用,且15 mg/L ATA和10 mg/L PASP复配时的缓蚀协同作用最好,缓蚀率高达99.89%.