Inhibition by tetradecylpyridinium bromide of the corrosion of aluminium in hydrochloric acid solution

The inhibition effect of tetradecylpyridinium bromide (TDPB) on the corrosion of aluminium in 1.0 M HCl solution was studied by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. The results show that TDPB is a very good inhibitor at little concentrations, and the adsorption of TDPB on aluminium surface obeys Langmuir adsorption isotherm. Polarization curves reveal that TDPB behaves as a cathodic inhibitor. EIS spectra consist of large capacitive loop at high frequencies followed by a large inductive one at low frequency values, and confirm the inhibitive ability.     

Nitrotetrazolium blue chloride as a novel corrosion inhibitor of steel in sulfuric acid solution

The inhibition effect of nitrotetrazolium blue chloride (NTBC) on the corrosion of cold rolled steel (CRS) in 0.5 M H₂SO₄ was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The results show that NTBC is a good inhibitor, and the adsorption of NTBC on CRS surface obeys Langmuir adsorption isotherm. Polarization curves show that NTBC acts as a mixed-type inhibitor. EIS spectra consist of large capacitive loop at high frequencies followed by a small inductive one at low frequency values, and charge transfer resistance increases with the inhibitor concentration.     

EIS study on pitting corrosion of 7150 aluminum alloy in sodium chloride and hydrochloric acid solution

The pitting corrosion behavior of 7150 aluminum alloy was studied by electrochemical impedance spectroscopy (EIS) in the sodium chloride and hydrochloric acid solution. Based on EIS features and corrosion morphologies as well as corrosion potential, the process of pitting corrosion could be clearly divided into four stages: at the first stage, the Nyquist diagram was composed of two overlapping capacitive loops at the high‐medial frequency and one inductive loop at the low frequency. At the second stage (metastable pits developing stage), there existed one small capacitive loop at the high frequency and one big capacitive loop at the medial frequency. At the third stage (stable pits developing stage), two time constants were more clearly distinguished, corresponding to two obvious capacitive loops. At the fourth stage, there appeared one capacitive loop, attributing to uniform corrosion. An equivalent circuit was designed to fit EIS, and the experimental results and the fitted results had good correspondence.     

Corrosion protection of Mg–5Li alloy with epoxy coatings containing polyaniline

The protective ability of epoxy coating containing polyaniline (PANI coating) on Mg–5Li alloy in 3.5% NaCl aqueous solution has been studied by means of EIS and electrochemical noise measurements (EN). The results of EN and EIS revealed that the PANI coating protected Mg–5Li alloy from corrosion perfectly. XPS results indicated that the presence of polyaniline changed the chemical structure of the corrosion film on the alloy surface. An analysis of the electrochemical noise data based on stochastic analysis indicated that the corrosion growth probability of Mg–5Li alloy beneath the coating was decreased by the addition of polyaniline.     

Investigation of erosion-corrosion of 3003 aluminum alloy in ethylene glycol-water solution by impingement jet system

Erosion-corrosion (E-C) of 3003 aluminum (Al) alloy in ethylene glycol-water solutions were studied by weight-loss and electrochemical measurements as well as surface characterization through an impingement jet system. Al alloy E-C is dominated by erosion components, i.e., pure erosion and corrosion-enhanced erosion, which account for 92-97% of the total E-C rate under the various conditions in this work. Contribution from corrosion components, including pure corrosion and erosion-enhanced corrosion, is slight. With the increase of fluid flow velocity and sand concentration, the total E-C rate increases. Compared with the significant increase of the rates of erosion components, the increase of the rate of corrosion component is negligible. Upon fluid flow, passivity of Al alloy that develops in static solution cannot be maintained, and an activation mechanism dominates the corrosion process of Al alloy. The effect of fluid impact angle on Al alloy E-C depends on the competitive effect of normal stress and shear stress. Under normal impact, the surface film would be broken and damaged, but still remain on the electrode surface to provide somewhat protection. With the decrease of impact angle, shear stress becomes dominant, and it would thinner and even completely remove the film. The enhanced surface irregularity of electrode under fluid impact is indicated by the presence of inductive loop in EIS plots. The effects of impact angle on electrode surface status and E-C rate are confirmed by surface morphology observation.     

Mechanism of corrosion of cast iron covered by aged corrosion products: Application of electrochemical impedance spectrometry

This work focuses on the corrosion of cast iron in a drinking water network. The study is performed in water and in a sandy soil saturated with the same water. In the presence of corrosion products, the inner wall surface shows a lower corrosion rate than the external wall. In the two media, impedance diagrams are described by a high-frequency loop characteristic of a protective corrosion layer and a diffusion impedance loop at low frequencies associated with oxygen diffusion. Different models involving mass transfer through a porous layer are suggested for the inner and the external corrosion layers.     

Corrosion evaluation of microarc oxidation coatings formed on 2024 aluminium alloy

Dense alumina ceramic coatings of 7 μm thickness were fabricated on 2024 aluminium alloy by microarc oxidation (MAO). The corrosion behaviour of the MAO coated alloys was evaluated using potentiodynamic polarisation and EIS measurements. The results show that the corrosion process of the coated alloy can be divided into three stages: (1) the initial stage (the first 2-6 h of immersion): penetration of corrosion medium into the aluminium alloy was inhibited by coating; (2) the second stage (after 24 h of immersion), corrosion medium penetrated to attack the interface between the substrate and the coating; (3) the final stage (after about 96 h): corrosion process was controlled by the diffusion of corrosion products.     

Al-Zn-Sn-Ga阳极腐蚀过程的电化学阻抗谱

通过测定Al-Zn-Sn-Ga阳极在3.5%NaCl(质量分数)溶液中浸泡不同时间的电化学阻抗谱(EIS),研究该阳极的腐蚀发展过程和腐蚀特征。结果显示:当合金刚被浸入3.5%NaCl溶液时,EIS谱为反应电阻很大的容抗弧,表明此时合金处于钝化态;随着浸泡时间的延长,EIS谱中高频段的容抗弧明显减小且低频段出现感抗弧,合金进入点蚀期;继续延长浸泡时间,EIS谱中除高频段的容抗弧和中、低频段感抗弧外,在低频段出现另一容抗弧,合金处于点蚀扩展期;随着浸泡时间的继续增加,低频段感抗弧消失,EIS谱由两个容抗弧组成,合金达到均匀腐蚀期。因此,合金的腐蚀由钝化态开始,经点蚀期和点蚀扩展期,达到均匀腐蚀期。     

Corrosion behaviour of AM60 magnesium alloys containing Ce or La under thin electrolyte layers. Part 1: Microstructural characterization and electrochemical behaviour

The corrosion behaviour of AM60 containing Ce or La (AMRE1) under thin electrolyte layers (TEL) in 3.5 wt.% NaCl solution was investigated by cathodic polarization and EIS. The results indicated corrosion resistance was enhanced by TEL decrease until 100 μm. There were three kinetic regions in polarization curves of AMRE1, whereas the second region disappeared for AM60. Meanwhile, EIS results showed capacitive loop at LFs for AMRE1 appeared under 200-300 μm thickness. The presence of second regions in polarization curves and capacitive loops at LFs in EIS was attributed to performance of new phases (γ) as indicated in microstructural characterization.     

两种氧化处理的铝合金空泡腐蚀行为的差异

对比研究了硬质阳极氧化和微弧氧化铝合金在3.5%NaCl溶液中的空泡腐蚀行为.结果表明:两种氧化铝合金的空泡腐蚀失重在第1h内都随着空化作用时间明显增大,此后则缓慢增大.超过4h之后,随着时间又迅速地增大.当硬质阳极氧化和微弧氧化两种膜的厚度相当时,氧化工艺对氧化铝合金的耐空泡腐蚀性能影响并不明显.在空泡腐蚀过程中,两种氧化处理铝合金的电化学过程都是受阴阳极混合过程控制.硬质阳极氧化铝合金的电化学阻抗谱为一变形的容抗弧,并且低频出现收缩,呈现多孔电极的阻抗谱特征.微弧氧化铝合金电极的电化学阻抗谱在高频区为一容抗弧,接着又为一容抗弧,低频区出现扩散阻抗谱特征.     

Inhibition effect of methyl violet on the corrosion of cold rolled steel in 1.0 M HCl solution

The inhibition effect of methyl violet (MV) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution at 20-50 °C was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) methods. The results show that MV is an excellent inhibitor even with very low concentration, and the adsorption of MV on CRS surface obeys Langmuir adsorption isotherm. Potentiodynamic polarization curves reveal that MV behaves as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of MV is also evidenced by SEM.     

A study of the corrosion behavior of gamma titanium aluminide in 3.5 wt% NaCl solution and seawater

Gamma titanium aluminide (γ-TiAl) was evaluated for corrosion resistance in 3.5% NaCl and seawater using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Polarization plots indicate very low corrosion rates although in both electrolytes the control samples lost passivity at low polarization potentials. Surface modification treatments were employed by oxidizing the samples in air at 500 °C and 800 °C with the purpose of improving corrosion resistance. While the surface treatments rendered γ-TiAl passive in the polarization experiments in both electrolytes, EIS tests showed that the oxide formed at 800 °C was not protective. EEC models are proposed to explain the EIS results for the three surface conditions tested.     

拉应力对7075铝合金的剥蚀及其电化学阻抗谱的影响

研究了拉应力对双级过时效(121℃/35 h+160/20 h ) 7075铝合金剥蚀的影响及合金在EXCO溶液中的电化学阻抗谱.研究表明，拉应力可显著地促进铝合金剥蚀的发生及发展.浸泡初期，合金电化学阻抗谱由一个高-中频容抗弧及一个中-低频感抗弧组成.合金一旦发生剥蚀，电化学阻抗谱上即出现一个高-中频容抗弧及一个中-低频容抗弧.     

Effect of niobium on the corrosion behaviour of low alloy steel in sulfuric acid solution

This study examines the effect of niobium (Nb) addition on the electrochemical properties of low alloy steel using electrochemical techniques in a 10 wt.% sulfuric acid solution as well as surface analysis techniques. The potentiodynamic test reveals the passive behaviour of all specimens and a decrease in the passive currents with increasing Nb content. Electrochemical impedance spectroscopy (EIS) shows that the Nb-containing steels have higher passive and charge transfer resistance than the control samples. These results suggest that the interaction of elements improves the corrosion resistance of low alloy steel due to the formation of Nb, C, S, P, and Fe products on the surface.     

Corrosion and electrochemical evaluation of an Al–Si–Cu aluminum alloy in ethanol solutions

The corrosion of aluminum alloy AlSi8Cu3Fe(Zn) in ethanol and ethanol solutions containing 10 vol.% water and 10 vol.% acetic acid, respectively, was investigated by means of electrochemical impedance spectroscopy (EIS), polarization curve, immersion, optical microscopy, scanning electron microscopy and element mapping. The Al alloy in the ethanol and its solutions exhibited a capacitive loop in the measured Nyquist EIS spectra at high frequencies, which can be attributed to the ethanol’s dielectric response. Addition of 10 vol.% acetic acid increased the ethanol corrosivity more significantly than the same amount of water addition. The Al–Si–Cu–Mg precipitated zones in the alloy were susceptible to corrosion attack due to the micro-galvanic effect by the Cu-containing precipitates.     

镍基合金718在H2S/CO2环境中的腐蚀行为研究

运用腐蚀失重和电化学测量技术,研究了镍基合金718在模拟苛刻油田环境中的H₂S/CO₂腐蚀行为。结果表明,在模拟高温高压H₂S/CO₂腐蚀环境中,718合金腐蚀轻微,表现出良好的抗均匀腐蚀和局部腐蚀能力。电化学测试结果表明,在模拟CO₂腐蚀环境中,718合金的阳极极化曲线存在明显的钝化区,而在模拟H₂S/CO₂腐蚀条件下的阳极极化曲线呈现多次活化-钝化转变现象,表明腐蚀产物膜的稳定性降低;EIS表明阻抗谱均有明显的容抗弧特征,不含H₂S时材料显示单一的容抗弧,加入H₂S时低频显示扩散阻抗控制,饱和CO₂溶液中718合金具有相对较大的极化电阻。     

Inhibiting effect of 2-mercaptobenzimidazole on the corrosion of Cu-30Ni alloy in aerated 3% NaCl in presence of ammonia

The inhibiting effect of 2-mercaptobenzimidazole (MBI) against Cu-30Ni alloy corrosion in aerated 3% NaCl polluted by ammonia, has been developed. Potentiodynamic and electrochemical impedance spectroscopy (EIS) measurements have been applied to determine the corrosion rate. scanning electron microscopy (SEM) studied surface morphology has been used to characterise electrode surface. The obtained results indicate that MBI acts as a good mixed-type inhibitor retarding the anodic and cathodic reactions. An increase of MBI concentration leads to a decrease of corrosion rate and inhibition efficiency increase.     

Initial corrosion protection of Zn–Mn alloys electrodeposited from alkaline solution

The effects of a deposition current density (c.d.) on the corrosion behaviour of Zn–Mn alloy coatings, deposited from alkaline pyrophosphate solution, were investigated by atomic absorption spectrophotometry (AAS), X-ray diffraction (XRD), atomic force microscopy (AFM), optical microscopy, electrochemical impedance spectroscopy (EIS) and measurement of corrosion potential (E_corr). XRD analysis disclosed that zinc hydroxide chloride was the main corrosion product on Zn–Mn coatings immersed in 0.5 mol dm⁻³ NaCl solution. EIS investigations revealed that less porous protective layer was produced on the alloy coating deposited at c.d. of 30 mA cm⁻² as compared to that deposited at 80 mA cm⁻².     

Electrochemical corrosion parameters of as-cast Al-Fe alloys in a NaCl solution

The aim of this study is to evaluate the general electrochemical corrosion resistance of Al-Fe alloys in the range of hypoeutectic compositions, Al-0.5 wt.% Fe and Al-1.5 wt.% Fe alloy. EIS plots, potentiodynamic polarization curves and an equivalent circuit analysis were used to evaluate the electrochemical parameters in a 0.5 M NaCl solution at 25 °C. It is shown that for an Al-0.5 wt.% Fe alloy, coarse cells tend to improve the corrosion resistance mainly due to the reduction in cellular boundaries and for an Al-1.5 wt.% Fe alloy, an opposite trend has been detected.     

Microwave-assisted synthesis of lanthanum conversion coating on Mg–Li alloy and its corrosion resistance

Lanthanum-based conversion coating on Mg–Li alloy has been prepared by a microwave-assisted method. X-ray diffractions (XRD) indicate that the intermetallic compounds of lanthanum are formed on Mg–Li alloy surface. Scanning electron microscopy (SEM) images show that the coating has different morphologies and special structures. The corrosion resistance was assessed by means of potentiodynamic polarization curves and electrochemical impedance spectra (EIS). The results indicate that this coating significantly reduces the corrosion rate of Mg–Li alloy in NaCl solution. A comparing experiment indicates that the coating prepared by microwave-assisted process has superior corrosion resistance to the coating obtained at room temperature.