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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: Humidity sensor based on thin micro-arc oxidation alumina (MOA) film was fabricated by a transient self-feedback control (TSFC) technique for the first time. The MOA film consisted of a polycrystalline nature of α and γ-Al2O3 phases, while high surface/volume ratio led to remarkable adsorption of the MOA film. Moreover, the humidity performance of the MOA sensor indicated good sensitivity of 8045.55 at 98% RH. Fast response and recovery times of the MOA sensor were 90s and 30s, respectively, at 20°C and 1000Hz. Exposing the MOA sensor to different humidities for longer durations indicated an excellent stability due to the α-Al2O3 phase in the MOA film. The mechanism in the sensor, to humidity, was explained by using equivalent circuits of (RC) and (C(RZ)). In the low RH range, the process was mainly dominated by the migration of protons through the adsorbed water molecule layer on the surface of the MOA film; while, in the high RH range, the process was due to the faster diffusion of protons in the single or multiple layers that were formed on the materials surface. [Copyright &y& Elsevier]

Abstract: This work for the first time reports a monolayer plasma electrolytic oxidation (PEO) coating on 2024 Al alloy substrate by transient self-feedback control (TSFC) mode. The monolayer coating without outer porous layer exhibits rather excellent compactness and corrosion protection attributed to extensive distribution of scattered ceramic particles with small size and less porosity. A possible mechanism is proposed to explain the formation of TSFC coating. Due to uniform surface distribution of the filming-formative particles and the discharge energy under high frequency square voltage (HFSV) waveform, the formation of the outer porous layer has been prevented effectively. [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: A Si-incorporated bioactive ceramic film was prepared on pure titanium by plasma electrolytic oxidation (PEO) in a new bath containing Ca2+, H2PO4 − and SiO3 2−. The film was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscope (XPS). The apatite-induced ability of PEO film was evaluated by soaking in a simulated body fluid (SBF) for various periods. The results showed that Si-incorporated PEO film present a porous microstructure, the pore size is around 1–5μm. The film mainly consists of anatase and rutile and a small amount of CaHPO4 and CaO, besides, bioactive compounds such as CaSiO3 and SiO2, also exist in the Si-incorporated PEO film. After immersion in SBF for 28 days, not only the surface layer but also the pores inside the Si-incorporated PEO film were completely filled by apatite crystals, whereas on the surface of a benchmark PEO film free of Si just present small piles of apatite crystals. Silicon incorporated into the PEO film provided more heterogeneous nucleation sites for apatite deposition and hence increased remarkably bioactivity of the PEO film. [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]

Purpose: The purpose of this paper is to investigate the interfacial conductivity and corrosion resistance of the Ni–P/Ti4O7 composite coating that is deposited on a carbon steel substrate as bipolar plates for proton exchange membrane fuel cells. Design/methodology/approach: The Ni–P/Ti4O7 coating was prepared by electroless plating. Scanning electron microscopy, white light interference, energy dispersive spectrometry and X-ray diffraction were used, respectively, to study the surface morphology, chemical composition and phase composition of coated samples. Electrochemical impedance spectroscopy, potentiodynamic and potentiostatic polarization were used to test the electrochemical performance and corrosion behavior. The interfacial contact resistance (ICR) was measured via the standard method. Findings: The surface of the Ni–P/Ti4O7 coating is complete and dense and without obvious defects. The electrochemical test results show that the Ni–P/Ti4O7 coating provides better corrosion resistance than the Ni–P coating and substrate. Compared with the Ni–P coating, the ICR of the Ni–P/Ti4O7 coating is lower by about 82.7%. This is because the coating has more conductive contact points. The more exciting thing is that the ICR of the Ni–P/Ti4O7 coating only increases to 12.38 mΩ·cm2 after 5 h of polarization. Originality/value: This paper provides a method for achieving surface modification of metal bipolar plates. Introducing Ti4O7 particles in the Ni–P layer reduces the contact resistance before and after polarization while ensuring good corrosion resistance. [ABSTRACT FROM AUTHOR]

• 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]

A flower ball shaped magnetic Fe 3 O 4 @MnO 2 core-shell catalyst has been synthesized and the average diameter is about 135–180 nm. The Fe 3 O 4 @MnO 2 (140.6 m2 g−1) showed a larger specific surface area than Fe 3 O 4 (64.6 m2 g−1) due to the thin film like nature of MnO 2. The Fe 3 O 4 @MnO 2 exhibited a great degradation performance for methylene blue (MB, 20 mg L−1, pH=7) after the addition of peroxymonosulfate (PMS, 0.18 g L−1) when the dosage of Fe 3 O 4 @MnO 2 is 0.3 g L−1, which reached 98% within 20 min. Additionally, the influences of catalyst dosage, PMS concentration and initial pH value of MB solution have been studied to maximize the catalytic performance of Fe 3 O 4 @MnO 2. Results showed that the increase of catalyst dosage and PMS concentration have improved the degradation efficiency and reaction rate of MB. However, the effect of pH on MB removal was complex and has been analyzed. According to XPS and quenching studies, the degradation effects of free radicals produced by catalyst-activated PMS on MB followed the order 1O 2 > •OH> SO 4 •−. This research demonstrates that Fe 3 O 4 @MnO 2 is an effective catalyst for the degradation of organic dye MB. [Display omitted] • A flower ball shaped magnetic Fe 3 O 4 @MnO 2 core-shell catalyst has been synthesized. • MB removal was pH dependent and has been analyzed. • The Fe 3 O 4 @MnO 2 exhibited high adsorption and catalytic degradation capacity toward MB. • This catalyst exhibited stability in catalytic activity. • The degradation pathway and catalytic mechanism were proposed. [ABSTRACT FROM AUTHOR]

• The PAM gels is a new corrosion-triggered inhibiting structure. • The inhibitor ions Ce4+ could change the morphology of the products film. • The absorption and bridging of PAM gels about the corrosion product. Biomaterial polyacrylamide (PAM) hydrogel was first studied for self-healing coatings of Mg alloys. In this work, a PAM gel with Ce4+ inhibitor was in-situ composited on the surface of micro-arc oxidation treated AZ31 Mg alloy. The results indicated that the scratched samples with the composite coating could avoid pitting corrosions and self-heal in neutral salt spray test (NSST). XPS and SEM-EDS analysis reveal that the self-healing performance was ascribable to the inhibition of Ce4+ and the bridge adsorption of PAM gels. Moreover, the results of open circuit potential and polarization curve indicate that the self-healing product film has good corrosion resistance. [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]