The electrochemical synthesis of poly(aniline-co-o-anisidine) on copper and their corrosion performances

The copolymer films PANI-co-POA and poly(aniline-co-o-anisidine) were carried out on copper (Cu) electrode, by applying two different scan rates (20 and 50 mV s⁻¹) and using two different thicknesses at high scan rate. Synthesizes were achieved under cyclic voltammetric conditions from 0.075 M aniline and 0.075 M o-anisidine containing sodium oxalate solutions. The synthesized copolymer films were strongly adherent and homogeneous in both cases. AC impedance spectroscopy (EIS), anodic polarization plots and open circuit potential–time curves were used to evaluate the corrosion performance of copolymer coated and uncoated electrodes in 3.5% NaCl. It was shown that the copolymer film coated at low scan rate exhibited a better property initially when compared with the copolymer film produced at high scan rate. However, it could not resist the attack of corrosion products, in longer time and meanwhile its barrier property significantly diminished. It was found that the thin copolymer film produced at high scan rate by its catalysing effect led to the formation of highly protective copper oxides on the surface whereby providing a better protection for long exposure times. It also emerged that the corrosion resistances of thin copolymer film produced at high scan rate and copolymer film synthesized at low scan rate were almost same and relatively higher for much longer periods when compared with the one observed for bare copper electrode.     

Protection of copper corrosion by modification of dodecanethiol self-assembled monolayers prepared in aqueous micellar solution

A novel method of preparing 1-dodecanethiol (DT) self-assembled monolayers (SAMs) on copper in aqueous micellar solution is explored. The resulting SAMs are characterized by XPS, contact angle tests and electrochemical measurements. It is found that DT dissolved in aqueous micellar solution can adsorb rapidly to the copper surface through strong thiolate bonds to form well-organized SAMs, which have properties comparable to those formed in ethanol solution. The electrochemical measurements show that the inhibition efficiency (IE) increases with an increase in the immersion time of copper in the aqueous micellar solution. After self-assembly for 1 h, the SAMs are able to effectively protect the underlying copper against corrosion in chloride-containing solution by hindering the cathodic process. Overall, the inhibition efficiency can reach 98.94%.     

Polyaniline for corrosion prevention of mild steel coupled with copper

Polyaniline emeraldine base/epoxy resin (EB/ER) coating was investigated for corrosion protection of mild steel coupled with copper in 3.5% NaCl solution. EB/ER coating with 5-10 wt% EB had long-term corrosion resistance on both uncoupled steel and copper due to the passivation effect of EB on the metal surfaces. During the 150 immersion days, the impedance at 0.1 Hz for the coating increased in the first 1-40 days and subsequently remained constant above 10⁹ Ω cm², whereas that for pure ER coating fell below 10⁶ Ω cm² after only 30 or 40 days. Immersion tests on coated steel-copper galvanic couple showed that EB/ER coating offered 100 times more protection than ER coating against steel dissolution and coating delamination on copper, which was mainly attributed to the passive metal oxide films formed by EB blocking both the anodic and cathodic reactions. Salt spray tests showed that 100 μm EB/ER coating protected steel-copper couple for at least 2000 h.     

Electrochemical corrosion characterization of Al-Ni alloys in a dilute sodium chloride solution

The aim of this study is to characterize the electrochemical corrosion resistance of Al-Ni alloy samples which were directionally solidified under upward unsteady state heat flow conditions. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques were used to analyze the corrosion resistance in a dilute 0.05 M NaCl solution at 25 °C. Equivalent circuit analyses were also conducted. It was found that microstructural features such as the dendritic arrangement and the distribution of Al₃Ni intermetallic particles have important roles on both the resulting pitting potential and the general corrosion resistance of Al-Ni alloys.     

Electrochemical synthesis of polyindole on 304-stainless steel in LiClO4–acetonitrile solution and its corrosion performance

The use of electrochemically synthesized polyindole (PIN) film was investigated for protective coating on 304-stainless steel (SS). Polyindole was deposited via anodic oxidation of the corresponding monomer, indole in acetonitrile (ACN) solution containing LiClO₄. It provided an adherent and stable coating on SS. The corrosion performance of coated and uncoated SS was investigated in 3.5% NaCl solution using electrochemical impedance spectroscopy (EIS), anodic polarization curves and open-circuit potential–time (E_ocp–t) diagrams. These tests demonstrated that PIN coating provided important barrier effect to SS for important immersion times in aggressive medium.     

Self-assembled 1-octadecyl-1H-1,2,4-triazole films on copper for corrosion protection

A film of 1-octadecyl-1H-1,2,4-triazole (OTA) was formed on a fresh copper surface by self-assembly technique. The optimum concentration of OTA and immersion time for the formation of a protective OTA film have been established using electrochemical impedance spectroscopy (EIS). These are (i) 15 mM concentration of OTA in methanol and (ii) immersion period of 48 h. X-ray photoelectron spectroscopy (XPS), reflection absorption FTIR spectroscopy, atomic force microscopy (AFM), and contact angle measurements have been used to characterize the OTA film on copper surface. The efficiency of OTA film to protect copper from corrosion in aqueous NaCl environment has been investigated using EIS, potentiodynamic polarization studies, cyclic voltammetry and weight-loss studies. All these studies showed that the OTA film affords excellent protection against corrosion of copper.     

Effect of nano-ZnO particles on the corrosion resistance of polyurethane-based waterborne coatings immersed in sodium chloride solution via EIS technique

Nano-composite coatings were formed by incorporating 3 wt% nano-ZnO in a polyurethane-based waterborne coating. The nano-ZnO based composite coatings were applied on standard phosphated steel panels by cathodic electrodeposition. The electrodeposited nano-composite coatings were then baked for 20 min at 165 °C. To investigate the corrosion resistance of the coatings, the coated panels were immersed in 3.5 wt% NaCl solutions for 2880 h (120 days). The improvement in corrosion performance of the composite coatings was evaluated using electrochemical impedance spectroscopy technique. It was found that the films containing nano-sized ZnO particles show a corrosion resistance of 2 orders of magnitude higher than that of the neat films.     

Coatings based on electronic conducting polymers for corrosion protection of metals

In this work, corrosion protection of mild steel by a novel epoxy resin (EP)-based coating system containing polyaniline (PAni) as an anticorrosive agent was studied. The corrosion behavior of mild steel samples coated with an EP/PAni-EB (emeraldine base), EP/PAni-ES (emeraldine salt), EP/SPAN (PAni sulfonated), EP/PAni-fibers, EP/PhoZn (zinc phosphate), EP/ChroZn (zinc chromate) or EP/Charge was investigated in 3.5% NaCl solution. For this purpose, electrochemical impedance spectroscopy measurements were utilized. It was found that the addition of three forms of PAni—undoped, sulfonated and fibers—to the EP resin increased its corrosion protection efficiency.     

Investigation of the first stages of the localized corrosion of pure copper combining EIS, FE-SEM and FE-AES

During the first 48 h that pure copper is submerged in a chloride containing solution, an oxide layer is formed that acts as a barrier layer between the aggressive solution and the substrate, offering some protection to the material. This barrier layer itself is subsequently attacked and localized corrosion is observed. The study of the corrosion behavior was based on open circuit potential (OCP) measurements. The evolution of this value was concurrent with the evolution of the state of the oxide layer. Furthermore the surface state was evaluated by taking impedance spectra every 2 h. This method proved to be insufficient to elucidate the surface evolution and additional techniques were employed. The thickness and the composition of the oxide layers as well as the different composition of the corrosion products in and around the zones of localized attack were determined by means of an FE-AES equipped with an ion gun. The scanning electron microscope (SEM) allowed us to visually discriminate between the three stages the surface passes through during the first 48 h. Mathematically the equivalent circuit used in literature fits the impedance data very well. The observations in this work are however in contradiction with the different physical meanings attributed to the circuit elements found in literature. Further research is necessary to reveal the real mechanism of copper corrosion in this sort of systems.     

Trimethylsilane-based pretreatments in a Mg-rich primer corrosion prevention system

A trimethylsilane-based coating was investigated as a pretreatment for Al-2024 T3 in a novel Mg-rich primer corrosion prevention system. SiC-based thin films were deposited onto Al substrates by plasma-enhanced chemical vapor deposition (PECVD). A screening study of the pressure (P) dependence of films deposited at 350 °C showed an increase in growth rate from 0.6 to 1.9 Torr. A second screening study where P was fixed at 1.9 Torr and temperature (T) was varied from 125 to 550 °C showed decreasing growth rates with increasing temperature with an apparent transition around 300 °C. Electrochemical impedance spectroscopy (EIS) of the SiC-based films on Al-2024 after exposure to a corrosive environment (i.e., dilute Harrison solution) indicated that samples coated using SiC-based films exhibit higher low frequency impedance (i.e., 100–1000× higher) than bare Al-2024 with open circuit potential remaining 0.1 V higher for the former suggesting the SiC-based films slow the corrosion process. A Mg-rich primer was coated onto the SiC on Al-2024 with the galvanic function of the system determined by EIS. As compared to SiC on Al-2024, a similar behavior for the low frequency impedance was observed for the Mg-rich primer-coated samples with some films exhibiting 1E + 8 Ω at 0.1 Hz indicating a strong barrier property. Initial gas jet erosion using acrylic media indicates the Mg-rich primer coatings are removed in preference to the Si–C films—the first step toward demonstrating a permanent pretreatment. When successfully developed and optimized, the value of such a hard, protective coating is the reduction of a three-component coatings system (i.e., pretreatment, primer, and topcoat) to a two-component system (i.e., primer and topcoat).     

Electrochemical noise and impedance study of aluminium in weakly acid chloride solution

The electrochemical noise (EN) characteristics of pure aluminium in unbuffered potassium chloride solution and with acetic acid/sodium acetate buffer at pH 5.4 and 4.3 have been analysed to throw light on the influence of pH and of the presence of buffer at the aluminium surface on chloride ion-induced corrosion. Comparison has been made with results obtained by electrochemical impedance spectroscopy (EIS) and quantitative deductions made concerning the values of the noise resistance and the magnitude of the electrochemical impedance. Deviations between results obtained by the two experimental techniques are discussed.     

Electrochemical synthesis of poly(5-nitroindole) on 316L-stainless steel in LiClO4-acetonitrile solution and its corrosion performance

The preparation of poly(5-nitroindole) (P5NI) coating was achieved on 316L-stainless steel (SS). Poly(5-nitroindole) was deposited via anodic oxidation of the corresponding monomer in acetonitrile (ACN) solution containing LiClO₄. The influence of P5NI coating against SS corrosion was studied in 3.5% NaCl solution by electrochemical impedance spectroscopy (EIS), anodic polarization curves and the open circuit potential–time (E_ocp–t) diagrams. The results obtained suggest that P5NI coating forms a sacrificial layer but the efficiency against corrosion is limited with increasing time.     

Application of multisine impedance spectroscopy, FE-AES and FE-SEM to study the early stages of copper corrosion

During the first 24 h of immersion of a pure copper surface in a NaCl containing solution, this surface is in constant evolution. The reactions going on the surface are still not known; discrepancies are found between different published studies. This study resolves these discrepancies using broadband impedance spectroscopy, field emission Auger spectroscopy and field emission electron microscopy. The surface evolution was studied using time series of impedance spectra. Also the experimental variables convection and electrolyte concentration were varied. Parameter evolutions were obtained by fitting the obtained impedance spectra to an equivalent circuit. Combining the calculated parameter values and their evolution with the spectroscopic data led to the identification or replacement of the elements present in the very general equivalent circuit found in the literature: a double layer, two circuit films in parallel and mass transfer.     

Concentration monitoring and performance of a migratory corrosion inhibitor in steel-reinforced concrete

Inhibitor concentration depth profiles for concrete samples treated with a proprietary migratory corrosion inhibitor (of the Cortec MCI range) are presented. The treated concrete was cored and these cores were then sectioned and crushed before being immersed in distilled water to extract the available inhibitor. The amine concentrations were quantified using an ammonium-sensing electrode and were then related to the inhibitor concentration present. The inhibitor examined, reported to contain a combination of volatile amines and amino carboxylate compounds, was found to readily diffuse through concrete. The inhibitor was subjected to a 5-year trial and found to be effective in suppressing corrosion of steel reinforcement in the presence of high chloride concentrations. The concentration profiles indicate that only relatively low concentrations of inhibitor were required to achieve inhibition in this case.     

电化学阻抗谱在缓蚀剂研究中的应用进展

概括了电化学交流阻抗谱的基本原理,介绍了电化学阻抗谱在缓蚀剂研究中的应用进展,并对电化学阻抗谱在腐蚀科学领域其他方面的应用进行了展望。     

Influence of rare earth Y on the corrosion behavior of as-cast AZ91 alloy

The influence of different contents of rare earth Y on the corrosion resistance of AZ91 alloy was investigated by the salt spray test and electrochemical measurements. It was found that the proper amount of Y was effective on improving the corrosion resistance of AZ91 alloy. The optimal modification effect was obtained when the Y content in the alloys was 0.3 wt.%. However, with the increase of rare earth Y, the corrosion rate became bigger slightly, and further addition of Y content over 0.3 wt.% resulted in the increment of the corrosion rate. It is suggested that the excessive rare earth Y can reduce the corrosion resistance of AZ91 alloy.     

1,2,3-苯并三氮唑铜缓蚀剂的研究进展

苯并三唑(BTAH)是一种非常有效的铜及其合金的缓蚀剂。到目前为止有许多关于BTAH缓蚀作用的研究,但其缓蚀机制仍然不为所知。对BTAH的缓蚀研究作出了总结,以便为进一步研究和开发新的高效缓蚀剂提供依据。     

Influence of pH on the synthesis and properties of polypyrrole on copper from phytic acid solution for corrosion protection

Polypyrrole (PPy) films were deposited on copper from “green” inhibitor of phytic acid solution for corrosion protection of copper. The corrosion protection property of the PPy layer was studied by an immersion test in a NaCl aqueous solution. The polymerization process of PPy on copper changed with the pH values of phytic acid solution and current density applied. When one oxidized bare copper in phytic acid solution at various pHs containing pyrrole monomer, a thin layer consisting of complex compound of Cu-phytate was firstly formed, followed by the formation of the PPy layer doped with phytate anion on the complex compound layer. The complex compound layer passivated the copper surface and its thickness increased with the lower pH value of the solution and the lower current density applied. It was found that the PPy coating prepared in the phytic acid solution at pH 4 exhibit the most protective property against copper corrosion.     

An environmentally friendly coating for corrosion protection of aluminum and copper in sodium chloride solutions

Triacetoxyvinylsilane (TAVS) has been used as precursor to prepare sol-gel under aqueous conditions for the surface treatment of aluminum and copper metals. The corrosion behavior of the sol-gel-treated metals has been investigated with cyclic voltammetry, potentiodyamic polarization and electrochemical impedance spectroscopy. Results from the electrochemical measurements have shown that the TAVS sol-gel-coated metal provided a better corrosion protection than the triethoxysilane (TES) sol-gel-coated metal due to the hydrophobic nature of vinyl group. Contact angle measurements have been conducted and the results have been applied to explain the degree of the corrosion protection of the coating film.     

Electrochemical corrosion characteristics of type 316 stainless steel in simulated anode environment for PEMFC

The corrosion behavior of type 316 stainless steel in simulated anode environment for proton exchange membrane fuel cell (PEMFC), i.e., dilute hydrochloric acid solutions bubbled with pure hydrogen gas at 80 °C, was investigated by using electrochemical measurement techniques. The main purpose is to offer some fundamental information for the use of stainless steels as bipolar plate material for PEMFC. Both polarization curve and electrochemical impedance spectroscopy (EIS) measurements illustrate that 316 stainless steel cannot passivate spontaneously in the simulated environments. The absorbed (and/or adsorbed) hydrogen atoms from cathodic corrosion reactions on the steel surface may deteriorate the passivity and corrosion resistance. The oxidation of these hydrogen atoms gives rise to a second current peak in the anodic polarization curve, and the current increases with immersion time. EIS spectra also reveal that a porous corrosion product layer formed on the steel surface during the active dissolution in the test solutions. 316 stainless steel exhibits the similar corrosion behavior in sulfate ions containing dilute hydrochloric acid solution.