Role of Chloride Ion and Dissolved Oxygen in Electrochemical Corrosion of AA5083-H321 Aluminum-Magnesium Alloy in NaC1 Solutions under Flow Conditions

Flow-induced corrosion consists electrochemical and mechanical components. The present paper has to assessed the role of chloride ion and dissolved oxygen in the electrochemical component of flow induced corrosion for AA5083-H321 aluminum-magnesium alloy which is extensively used in the construction of high-speed boats, submarines, hovercrafts, and desalination systems, in NaCI solutions. Electrochemical tests were carried out at flow velocities of 0, ：2, 5, 7 and 10 m/s, in aerated and deaerated NaCI solutions with different sodium chloride concentrations. The results showed that the high rate of oxygen reduction under hydrodynamic conditions causes an increase in the density of pits on the surface. The increase of chloride ions concentration under flow conditions accelerates the rate of anodic reactions, but have no influence on the cathodic reactions. Thus, in the current work, it was found that under flow conditions, due to the elimination of corrosion products inside the pits, corrosion resistance of the alloy is increased.     

Role of Chloride Ion and Dissolved Oxygen in Electrochemical Corrosion of AA5083-H321 Aluminum-Magnesium Alloy in NaCl Solutions under Flow Conditions

Flow-induced corrosion consists electrochemical and mechanical components. The present paper has to assessed the role of chloride ion and dissolved oxygen in the electrochemical component of flow induced corrosion for AA5083-H321 aluminum-magnesium alloy which is extensively used in the construction of high-speed boats, submarines, hovercrafts, and desalination systems, in NaCl solutions. Electrochemical tests were carried out at flow velocities of 0, 2, 5, 7 and 10 m/s, in aerated and deaerated NaCl solutions with different sodium chloride concentrations. The results showed that the high rate of oxygen reduction under hydrodynamic conditions causes an increase in the density of pits on the surface. The increase of chloride ions concentration under flow conditions accelerates the rate of anodic reactions, but have no influence on the cathodic reactions. Thus, in the current work, it was found that under flow conditions, due to the elimination of corrosion products inside the pits, corrosion resistance of the alloy is increased.     

AA6063铝合金着色Zr无铬转化膜及其电化学性能

以锆盐为主要原料,实现常温下对AA6063铝合金的无铬化学转化处理。采用SEM,XRD及电化学测试研究了转化膜的性能。结果表明:锆膜生长是以针状小单元结构组织成圆形较大的单元,再发展为均匀的黑灰色转化膜;锆膜厚约8.79μm,主要由KZrF_3(OH)_2·H_2O及KZrF_3O·2H_2O组成;锆膜耐腐蚀性能比铝合金提高了数百倍,与铬酸盐转化膜相当;锆膜的耐腐蚀性能与后处理工艺有一定关系,膜层结构等效电路为R_1+C_2/R_2+M_3。     

阴树脂粉末对换流站阀冷系统6063铝合金腐蚀的影响

为了研究UP6150阴树脂粉末对阀冷系统6063铝合金腐蚀的影响,在(50±1)℃下通电(10 m A直流电流)与不通电情况下进行了6063铝合金浸泡腐蚀试验,200 m L去离子水中加0,6,10 g阴树脂粉末,将6063铝合金浸泡不同天数测定试样腐蚀速率,分析了表面形貌及溶液中离子含量,并进行相关的电化学测试。结果表明:在通电与不通电的情况下,阴树脂粉末均加速6063铝合金腐蚀,阴树脂粉末浓度越大,腐蚀越严重; 50℃时阴树脂粉末分解,生成腐蚀性离子,加速了铝合金的腐蚀;腐蚀产物中含有大量的C、O、Al,还含有少量的N,表明阴树脂分解产物参与腐蚀过程,生成Al N(Al N-R),对铝合金造成腐蚀; 6063铝合金在阴树脂粉末溶液中自腐蚀电位负移,自腐蚀电流密度增大。     

Electrochemical Properties of MNZh 5-1 Alloy in an Inhibited Washing Solution Based on Acetic and Nitric Acids

We use the method of weight, polarization, and impedance tests for studying the mechanism of protection using YuTE-6, YuTE-7, YuTE-8A, YuTe-8B, and USK-4 inhibitors of acid corrosion in washing solutions based on acetic and nitric acids aimed at removal of deposits from the surface of condenser pipes made of MNZh 5-1 alloy at a temperature of 60°C. We show that the inhibitors retard the cathodic and anodic reactions and lead to a decrease in anodic dissolution. They form a chemisorption film on the surface resistant in the range of corrosion potentials. The vulnerability Z is equal to 92–96%, which is greater than that of benzotriazole (Z = 80%) widely used for this purpose. The proposed inhibitors can be used for the efficient removal of deposits from condenser pipes made of MNZh 5-1 alloy.     

09Cr2AlMoRE钢和N80油套管钢的CO2腐蚀电化学行为

利用交流阻抗技术对比研究了N80油套管钢和09Cr2AlMoRE钢（称新型合金）在饱和CO2的地层水中的腐蚀电化学行为,同时利用SEM观察了两种材料在1MPa,120℃腐蚀7d（天）所成膜的形貌。结果表明,N80钢的阳极电化学阻抗谱出现了高频的容抗弧、中低频的感抗弧和低频的容抗弧;而新型合金的阳极电化学阻抗谱只出现了高、低频容抗弧,感抗弧已很少了。对于阴极电化学阻抗谱,N80钢的阻抗谱只由一容抗弧组成,而新型合金则由高频容抗弧、中频Warburg阻抗和低频容抗弧共同组成。对两种材料阴、阳极过程中极化电阻的计算表明,新型合金阴、阳极过程中的极化电阻大于N80钢相应过程的极化电阻,表明新型合金能有效地抑制了CO2腐蚀。     

Hydroxyapatite microparticles as feedback-active reservoirs of corrosion inhibitors

This work contributes to the development of new feedback-active anticorrosion systems. Inhibitor-doped hydroxyapatite microparticles (HAP) are used as reservoirs, storing corrosion inhibitor to be released on demand. Release of the entrapped inhibitor is triggered by redox reactions associated with the corrosion process. HAP were used as reservoirs for several inhibiting species: cerium(III), lanthanum(III), salicylaldoxime, and 8-hydroxyquinoline. These species are effective corrosion inhibitors for a 2024 aluminum alloy (AA2024), used here as a model metallic substrate. Dissolution of the microparticles and release of the inhibitor are triggered by local acidification resulting from the anodic half-reaction during corrosion of AA2024. Calculated values and experimentally measured local acidification over the aluminum anode (down to pH = 3.65) are presented. The anticorrosion properties of inhibitor-doped HAP were assessed using electrochemical impedance spectroscopy. The microparticles impregnated with the corrosion inhibitors were introduced into a hybrid silica-zirconia sol-gel film, acting as a thin protective coating for AA2024, an alloy used for aeronautical applications. The protective properties of the sol-gel films were improved by the addition of HAP, proving their applicability as submicrometer-sized reservoirs of corrosion inhibitors for active anticorrosion coatings.     

The effect of extrusion speed on the structure and corrosion properties of aged and non-aged 6063 aluminum alloy

Extrusion is used in processing of Al alloy for consolidation, redistribution of reinforcements, and shape forming. The important parameter that controls the extrusion process is extrusion rate, which is a function of extrusion equipment and parameters. Homogenized AA6063 alloy billets were extruded at different ram speeds related to extrusion speed (3, 6, 10 mm s⁻¹) and then aged at 185 °C for 6 h. The extruded samples were studied for their corrosion, microstructure, and mechanical properties. The effects of extrusion speed and aging on the corrosion behavior of AA6063 were investigated using dynamic polarization and impedance techniques in 0.5 M NaCl aqueous solution. The surface structures were then characterized by means of surface profilometer. The electrochemical measurements showed that the decreasing ram speed for the aged sample improved the corrosion resistance. In addition, the aging improved the corrosion resistance of aluminum in 0.5 NaCl environments.     

EIS Study on Pitting Corrosion of AA5083-H321 Aluminum-Magnesium Alloy in Stagnant 3.5% NaCl Solution

In this research, EIS （electrochemical impedance spectroscopy） technique was utilized to study the pitting corrosion behaviour of AA5083-H321 aluminum-magnesium alloy in 3.5% NaCl solution. Impedance spectra were obtained during 240 h of exposure of the sample to the test solution. The surface and cross-section of the samples were studied by scanning electron microscopy （SEM） and EDAX （energy dispersive analysis of X-ray） analysis. The results indicated that as the resistance of the passive layer on intermetallic particles is very small, this parameter on the sample surface layers is controlled by that of pure passive layer. However, the capacitors in the proposed equivalent circuit are replaced with the constant phase elements （CPE）, due to non-uniformity and occurrence of pitting corrosion on the surface. The outward diffusion of Al^＋3 ions through the passive layer and the thickening of this layer cause the impedance decrease in the first 24 h and increase afterwards. The detachment of intermetallic particles from some of pits and the accumulation of the corrosion products inside some others are factors that prevents the continuation of cathodic reactions on the top of the intermetallic particles.     

有机羧酸在铸铝/中性冷却水体系中的缓蚀作用研究

为了提高中性冷却水系统中铸铝的耐腐蚀性能,通过极化电阻、稳态极化曲线和交流阻抗等电化学方法研究了不同比例一元、二元有机羧酸混合溶液对铸铝的缓蚀性能.结果表明,常温状态下一元、二元有机羧酸的比例对其缓蚀性能有较大的影响,当二者的比例为1:1时缓蚀效果最佳.有机羧酸对铸铝有较好的缓蚀效果,能同时有效地抑制中性冷却水系统中铸铝的阴阳极过程,表现为混合型缓蚀剂.     

A filiform corrosion and potentiodynamic polarisation study of some aluminium alloys

The aim of the present investigation is a combined study of filiform corrosion of aluminium alloys by accelerated exposure tests and potentiodynamic polarisation measurements. The accelerated exposure tests are performed on binary Al-Cu, Al-Mg, Al-Si and Al-Zn model alloys, a ternary Al-MgSi alloy and on the two commercial alloys, AA2024-T351 and AA7075-T651, with variations of composition and surface treatments. The surface treatments cover simple degreasing, chromate and cerium based treatments. A trend of a higher filiform corrosion susceptibility with increasing alloying elements concentrations was observed for all model systems. Furthermore, the filiform corrosion susceptibility varies with the solute atom, in particular Cu was found to have a detrimental effect on the filiform corrosion properties. Both chromating and cerating improve the filiform corrosion resistance of the alloys significantly. To explain the trends observed in the exposure tests, polarisation measurements were performed on the untreated Al-Cu and Al-Zn alloys in bulk anolyte and catholyte solutions which are characteristic for the local anodic and cathodic sites in the filaments on the aluminium substrates. From these measurements a filiform corrosion current, defined as the intercept of the anodic and cathodic curves, can be determined. The present set of experiments shows a correlation between the filiform corrosion properties during accelerated exposure tests and the potentiodynamic polarisation measurements for the Al-Cu alloys. When comparing the results for the Al-Cu and Al-Zn binary alloys it can be concluded that the correlation factor differs significantly with the solute atom and the filiform corrosion current proves to be a non-uniquely discriminating parameter for the filiform corrosion susceptibility of the model alloys. The difference in correlation factor for the Al-Cu and Al-Zn alloys is attributed to differences in the electrochemical behaviour of these alloys with local variations in substrate composition. For the Al-Cu and Al-Zn model alloys the filiform corrosion initiation characteristics are related to the passive range and thus implicitly to the ease of pitting of the alloy. A smaller passive range corresponds to a higher filiform site density for both the Al-Cu and Al-Zn alloys.     

Effect of heat treatment on the Inhibition of the acidic corrosion of aluminum alloy

The effect of heat treatment on the inhibition of acid corrosion of duralumin has been studied using gasometry, mass loss measurements and potentiodynamic technique. All the data reveal that the duralumin generally developed good corrosion resistance after heat treatment and the corrosion rate ranked as follows: Non treated > Naturally aged > quenched. This improvement in the corrosion resistance was attributed to the structural homogeneity of the heat-treated alloys. The presence of some selected aryl and alkyl triazoline derivatives at the thershold concentration of 5 × 10^?3 M indicate that these compounds retard the corrosion rate of duralumin and the extend of inhibition depends on the molecular structure of the inhibitors. Polarization curves show that the triazoline compounds act as mixed-type inhibitors affecting both the cathodic and anodic process. Moreover, there is no noticeable difference in the degree by which the triazoline derivatives inhibit the corrosion of pure aluminium and heat treated duralumin alloy.     

Deposition and corrosion behavior of silicate conversion coatings on aluminum alloy 2024

Potassium silicate was deposited on AA2024 aluminum alloy as environmentally friendly conversion coatings and its corrosion behavior were examined by means of electrochemical impedance spectroscopy, potentiodynamic polarization and surfaces techniques. Potentiodynamic polarization curves show significant decrease in corrosion current density of silicate coated aluminum in NaCl solution. The corrosion resistance was increased with increasing silicate concentration of coating baths. The results indicated that the coating applied from 3 molar silicate baths is more uniform and continuous. The X‐ray diffraction (XRD) and energy discharge spectroscopy (EDS) spectra confirm the existence of silicate film on the AA2024 surface. The coating performance was evaluated in acidic and basic NaCl solution and the results show the stability of silicate conversion coating in these solutions.     

铜离子及电位对5083铝合金阴极保护行为的影响

目前有关船体防污涂料中的铜离子及阴极保护电位对铝合金船体的腐蚀电化学研究不够深入。通过极化试验、电化学阻抗谱(EIS)测试及外加恒电位阴极保护试验,并结合腐蚀形貌观察,研究了5083铝合金在有无Cu~(2+)的3.5%NaCl溶液中的极化及腐蚀特性,并结合不同电位下的阴极保护行为,探讨了其阴极保护电位范围。结果表明:防污剂中的Cu~(2+)沉积在铝合金基体表面会造成防腐蚀性能下降,降低铝合金舰船的阴极保护效果,应该避免Cu~(2+)的渗入;阴极保护电位过正,保护效果不佳,会造成铝合金表面发生点蚀,但若阴极保护电位过负,表面会发生析氢腐蚀,因此其合理的阴极保护电位范围为-1.00~-1.10 V(vs SCE)。     

Synthesis of a new family of Schiff base nonionic surfactants and evaluation of their corrosion inhibition effect on X-65 type tubing steel in deep oil wells formation water

Some new Schiff base nonionic surfactants were synthesized and characterized using FTIR and ¹H NMR spectroscopy. The corrosion inhibition effect of the synthesized surfactants on X-65 type tubing steel in deep oil wells formation water has been studied by polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. Polarization data indicate that the selected surfactants act as mixed type (cathodic/anodic) inhibitors. EIS results show that the change in impedance parameters with the concentration of the surfactants studied is indicative of the adsorption of surfactant molecules on carbon steel surface. The adsorption of the inhibitors was well described by the Langmuir adsorption isotherm. Effect of temperature on the efficiency of the corrosion inhibition process was studied and the values of activation energy, enthalpy of activation and entropy of activation were calculated and discussed. The corrosion inhibition efficiency of the surfactants is correlated with surface tension measurements data. The protective film formed on the carbon steel surface was studied by scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDX) techniques.     

碳酸钠在氯化钠溶液中对铝合金的缓蚀作用研究

应用电化学实验方法和扫描电子显微镜（ＳＥＭ）研究了碳酸钠在氯化钠溶液中对铝合金缓蚀作用。实验结果表明,碳酸钠对铝合金具有较好的缓蚀作用,在一定程度上抑制了铝合金的点蚀。这种缓蚀作用主要是通过在铝合金表面形成一种化学转化膜和抑制阴极过程实现的。     

模拟2倍浓缩海水中聚环氧琥珀酸和Na2MoO4对304不锈钢的缓蚀作用

为开发适用于循环冷却海水／不锈钢体系的绿色缓蚀剂,采用电化学阻抗谱、极化曲线及表面腐蚀形貌分析,研究了聚环氧琥珀酸（PESA）、Na2MoO4在模拟2倍浓缩海水中对304不锈钢的缓蚀作用。结果表明：在模拟2倍浓缩海水中,PESA与Na2MoO4均能在304不锈钢表面形成保护膜,产生缓蚀作用;PESA为阳极吸附型缓蚀剂,...     

喹啉-2-甲醛对AA5052铝合金早期腐蚀的检测

为寻找适用于监测金属早期腐蚀的方法,以喹啉-2-甲醛作为荧光探针,测试了铝合金5052(AA5052)在1%Na Cl溶液中的早期腐蚀过程。通过荧光光谱法测定了溶液的荧光光谱强度与AA5052腐蚀产生的Al3+浓度之间的线性关系,以考察铝合金的腐蚀程度;采用电化学交流阻抗、电感耦合等离子体发射光谱法、表面形貌观察及能谱测定对荧光分析结果进行了分析、验证。结果表明,该方法具有较高的灵敏度和准确性。     

Characterization of the protective effect of aluminium surface treatments by d.c. and a.c. measurements

Steady-state and electrochemical impedance spectroscopy measurements have been made on anodic layers on 1050 and 2024T3 aluminium alloys prepared from solutions of phosphoric acid, boric acid and sodium tetraborate, before and after impregnation treatment with zinc. Corrosion characteristics of the anodic layers were dependent on the aluminium substrate and the electrolyte. Aluminium alloy composition was found to be the most important factor for corrosion resistance; alloying elements of 2024T3 alloy (like copper) had a harmful influence on this layer property. Steady-state measurements allowed the oxide layer behaviour to be studied in the anodic range by the determination of an anodic passivity domain. This domain was characterized by a weak aluminium oxidation through the oxide layer. The zinc impregnation treatment had a marked protective effect on each studied anodic layer. This treatment can be used as an alternative to hot sealing in water or chromic acid solution.     

Inhibitive Effect of Some Aldehydes on Corrosion ofAl-3Mg Alloy in Acid Solutions

The inhibitive action of some aldehydes towards the corrosion of Al-3Mg alloy in 2M hydrochloric acid solution has been invedigated using polarization and weight loss measurements. The two methods give the same order of inhibition effeciency Polarization Studies reveal that cathodic polarization is more pronounced than anodic one. The results indicate that all the compounds Studied are excellent corrosion inhibitors and the percentage efficiency varying with both the type and concentration of the inhibitor and being in the following order: p-methoxy-benzaldehyde (1)>benzaldehyde (2)>p-chlorobenzaldehyde (3)> p-nitrobenzaldehyde (4). The degree of surface coverage of the adsorbed additives was determined and the results obey the Langmuir isotherm.Effect of temperature on the corrosion rate in absence and prance of different concentrations of the used inhibitors was investigated using weight loss measurements. The results indicate that the corrosion rate rapidly increases with increasing temperature. Arrhenius parameters have been calculated and discussed.