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Abstract: A micro-arc oxidation alumina (MOA) support filled with a CsH2PO4 proton conductor was investigated as an inorganic composite electrolyte for a H2/O2 solid-acid fuel cell (SAFC). The MOA support was polycrystalline and contained α- and γ-Al2O3 phases; while, the proton conductor CsH2PO4 formed an interlaced network within the MOA support. The single-module SAFC using the fabricated MOA/CsH2PO4 membrane delivered a peak power of ∼38.5 m W cm−2 and a proton conductivity of ∼2.1 m S cm−1 at a low temperature (25 °C). Compared to a SAFC using an anodic alumina membrane composite electrolyte (AAM/CsH2PO4 SAFC), which displayed rapid degradation, the SAFC using the MOA/CsH2PO4 composite electrolyte showed improved stability with cycling. This was attributed to the crystalline α-Al2O3 phase that was part of the MOA support that had increased the chemical resistance. [Copyright &y& Elsevier]

Highlights: [•] Phytic acid increases compactness of self-assembled nanoparticle (SANP) film. [•] SANP-P layer in composite film indicates good barrier property against corrosion. [•] Improved adhesion of composite film obtained in a corrosive service environment. [•] SANP film with phytic acid (SANP-P) shows high thermal stability. [ABSTRACT FROM AUTHOR]

Abstract: Two microwave absorbing coatings (MACs) are applied onto magnesium alloy substrate and are studied using electrochemical impedance spectroscopy (EIS) during immersion in 3.5% NaCl solution. The diffusion behavior of electrolyte through the MACs was firstly studied. The result shows that electrolyte transfers significantly fast in carbonyl iron loaded coating than barium ferrite loaded coating. In order to account for the distribution of different absorbents on corrosion process, a modified equivalent circuit with a distribute transmission line model was proposed to fit EIS spectra of MACs. Simulated EIS diagrams agree very well with experimental spectra of 25% and 50% PVC MACs. Moreover, simulation data was studied to analyze degeneration of two MACs. The result shows that the corrosion of CI particles plays an important role for failure of CI coating, but the degeneration of BF coatings which were slower than CI coating was ascribed to defects within the coating. [Copyright &y& Elsevier]

Abstract: A composite three-layer film was prepared on AZ31B Mg alloy for corrosion protection by means of plasma electrolytic oxidation (PEO), self-assembled nanophase particle (SANP) and electroless nickel (EN) plating. Structure and corrosion protection were characterized by various analytical instruments and electrochemical methods. Experiment results indicated that the composite film consisted of compact EN plating and coherent bilayer film, which provided effective protection for Mg alloy against galvanic corrosion and long-term immersion corrosion. [Copyright &y& Elsevier]

Abstract: Protective composite coatings were prepared on magnesium alloy AZ91D by micro-arc oxidation (MAO) treatment plus a top coating with sealing agent using multi-immersion technique under low-pressure conditions. The corrosion resistance of AZ91D alloy with composite coatings was superior evidently to that with merely MAO film. SEM observations revealed that the sealing agent was integrated with MAO film by physically interlocking; therewith covered uniformly the surface as well as penetrated into pores and micro-cracks of MAO film. The anti-corrosion properties in 3.5% NaCl solution of the composite coatings were evaluated by using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Based on the results of chronopotentiometric (E ∼ t) and EIS measurements for long time immersion in 3.5% NaCl solution, appropriate equivalent circuits for the composite coatings system were proposed. It follows that due to the blocking effect of the sealing agent in pores and cracks in MAO film, the composite coatings can suppress the corrosion process by holding back the transfer or diffusion of electrolyte and corrosion products between the composite coatings and solution during immersion. [Copyright &y& Elsevier]

• Pulse current make the potential distribution of concrete more uniform compared to direct current. • Increasing current density will increase the total concrete desalination efficiency. • Total concrete resistance increases during ECR process. • Pulse current repair is a suitable method to improve the efficiency of chloride removal. Electrochemical chloride removal (ECR) technique as an effective repair method has been applied to chloride-attacked concrete structures. This research studies the influence of different external electrical fields on the ECR treatment for reinforced concrete. Two types of electrical fields including direct and pulse current with average current densities of 2, 3 and 4 A/m2 were investigated. The chloride ion content of concrete before and after ECR treatment was determined. The results show that no matter what current density was used for concrete repair, the effect of pulse current on the desalination of concrete was better than direct current. Also, increasing the current density can also promote the concrete chloride removal efficiency. When applying a current density of 4 A/m2 to the steel rebars for 28 days, the remained chloride concentration of the concrete after ECR treatment was obviously lower than that of using 2 and 3 A/m2. In addition, the half-cell potential method was used to evaluate the rebar potential distribution. It was found that the pulse current can make the cathode reinforcement arranged in parallel in the concrete have a more uniform potential distribution, which indicates that the applied electrical current is easier to uniformly pass through the whole concrete structures. [ABSTRACT FROM AUTHOR]

In this paper, a new approach of bidirectional electro-migration rehabilitation (BIEM) using pulse currents was proposed. The effect of the duty cycle and frequency of the square wave pulse current on the BIEM was investigated. The results showed that the desalination efficiency was improved by 10 % with the decrease of duty ratio and frequency. Furthermore, With the increase of duty ratio and frequency, the hydrogen permeation of steel bars decreased by 28.5 %. More uniform desalination efficiency was obtained by using pulse current. The half-cell potential of the rebars was also measured and it was higher for the samples using pulse currents than for those using direct currents, indicating a lower risk of corrosion after pulse current treatment. The pH value of the concrete also increased during the BIEM process. • The amount of hydrogen permeation in the rebars of concrete repaired by pulse current is reduced. • Increasing frequency and decreasing duty cycle of pulse current make the desalination efficiency distributed more evenly. • Decreasing frequency and duty cycle of pulse current will increase the efficiency of chloride ions removal. [ABSTRACT FROM AUTHOR]

Abstract: After being pre-plated a zinc layer, an amorphous Al–Mn alloy coating was applied onto the surface of AZ31B magnesium alloy with a bath of molten salts. Then the corrosion performance of the coated magnesium alloy was examined in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the single Zn layer was active in the test solution with a high corrosion rate while the Al–Mn alloy coating could effectively protect AZ31B magnesium alloy from corrosion in the solution. The high corrosion resistance of Al–Mn alloy coating was ascribed to an intact and stable passive film formed on the coating. The performances of the passive film on Al–Mn alloy were further investigated by Mott-Schottky curve and X-ray photoelectron spectroscopy (XPS) analysis. It was confirmed that the passive film exhibited n-type semiconducting behavior in 3.5% NaCl solution with a carrier density two orders of magnitude less than that formed on pure aluminum electrode. The XPS analysis indicated that the passive film was mainly composed of AlO(OH) after immersion for long time and the content of Mn was negligible in the outer part of the passive film. Based on the EIS measurement, electronic structure and composition analysis of the passive film, a double-layer structure, with a compact inner oxide and a porous outer layer, of the film was proposed for understanding the corrosion process of passive film, with which the experimental observations might be satisfactorily interpreted. [Copyright &y& Elsevier]