Three kinds of surface treatments, including permanganate, molybdate, and phytic acid conversion films, were fabricated on La-Ce mischmetal containing AM60B magnesium alloy. Their effects on the corrosion and tribological behaviors of the alloy in 3.5 wt% NaCl solution were systematically investigated via Mott–Schottky analysis, electrochemical measurements, and friction–wear tests. The results show three surface treatments shift the flat band potential in the negative direction, reduce the corrosion current density, enlarge the electrochemical impedance arc radius, and decrease the friction coefficient, conferring remarkably enhanced corrosion and wear resistance to the alloy substrate. The performance enhancement is ascribed to the formation of uniform, dense conversion films that act as effective physical barriers, which impede the penetration of corrosive species, isolate the substrate from the aggressive aqueous environment, and improve the chemical and electrochemical stability of the alloy–solution interface. The comprehensive performance ranking of the three surface treatments in terms of corrosion and wear resistance is as follows: permanganate conversion film > molybdate conversion film > phytic acid conversion film.

Compared with the proton exchange membrane fuel cell (PEMFC),the anion exchange membrane fuel cell (APEMFC) using non-noble metal as their catalyst not only improve the cathodic oxygen reduction reaction (ORR) dynamics,but also reduce costs and the plate corrosion.APEMFC has become a hot research topic in the new energy field.In this paper,the developments of non-noble metal catalysts for oxygen reduction in APEMFCs were reviewed.On the basis of this,the porous nano carbon materials doped with hetero atoms and the non-noble metals supported on the carrier were proposed,which could be the future development direction of APEMFC cathode catalyst.

Amorphous hydrated manganese dioxide (MnO2) was prepared as an electrode material for supercapacitors by liquid co-precipitation in the presence of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG) and sodium dodecylbenzenesulfonate (SDBS) respectively. The obtained samples were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical methods. Physical characterizations confirmed that the addition of surfactants played an important role in the preparation of MnO2. The specific surface areas of MnO2 with the addition of PEG, SDBS and PVP were 169.92 m2/g, 137.40 m2/g and 196.64 m2/g, respectively, and the corresponding capacitances were 207.9 F/g, 187.5 F/g and 238.7 F/g. Compared with the sample without surfactants, the specific surface area and capacitance of the sample with the addition of PVP were improved by 92.2% and 53.1%, respectively. Moreover, the electrode showed good cycle stability at the current density of 120 mA/g, and 91.1% of its specific capacitance still remained after 500 cycles. It was concluded that this performance improvement was attributed to the electrostatic stabilization of the multivariate alkyl residue and cyano group (-NCO) as anchoring group, as well as the steric hindrance effect from lateral polarity groups of pentabasic ring in PVP structure.

The research progresses of carbon-based catalysts for oxygen reduction in anion exchange membrane fuel cell (AMFC) were reviewed in detail.The application feasibility of heteroatom doped carbon-based catalysts in AMFC was also analyzed.On this basis,heteroatom doped porous nano-carbon materials should be the potential materials of cathodic catalysts for anion exchange membrane fuel cells.

Hydrxoyapatite-chitosan-RuCl3 nanocomposite coatings were pulsed electrochemical deposited on magnesium alloys AZ91D and studied using scanning electron microscope (SEM), X-ray diffraction (XRD), energy-dispersion spectrometer (EDS), electron probe micro-analysis (EMPA), auger electron spectroscopy (AES) and Fourier transform infrared spectroscopy (FTIR). The corrosion resistance of coating was examined by impedance measurements and potentiodynamic polarization. It was shown that the coatings can be varied by the variation of RuCl3 concentration in the solutions used for pulsed electrochemical deposition (PED). The absorption rate of Ru element on composite coatings was varied in the range of 35.02%similar to 51.62% by the variation of RuCl3 concentration from 2.1 mmol L-1 to 8.4 mmol L-1 in electrolyte. The hydroxyapatite grain of the obtained coating was refined to 180 nm, which could be explained by this mechanism: the electronegativity value of Ru was higher than Ca, which resulted in the new formation of PO43- tended to prefer attracting RuCl3 firstly on the cathode. Moreover, electrochemical impedance spectroscopy and potentiodynamic polarization studies showed that higher RuCl3 absorption rate on the coating provide corrosion protection of AZ91D in Hank's solution. With higher RuCl3 absorption rate, the induced hydroxyapatite-forming ability of the composite coating in Hank's solution has improved remarkably. The composite coatings are promising materials for the fabrication of implantable bio-materials with advanced functions properties. (C) 2015 Elsevier B.V. All rights reserved.

Objective To set up the life prediction model of the coating based on the grey theory and use the model to calculate the coating life of the solvent-free coal tar epoxy coating with different thicknesses in coastal chloride salt soil simulation. Methods By electrochemical methods, the electrochemical impedance spectroscopy of carbon steel with the solvent-free coal tar epoxy coating of different thicknesses in the simulated solution of coastal chloride salt soil was obtained. Based on the GM(1,1) model of grey theory and the relationship between the low frequency impedance modulus value and the immersion time, the prediction model of the impedance modulus at the low frequency for the coating was established in the simulated solution of coastal chloride salt soil. Results The low-frequency impedance modulus value still remained above 8. 3×108Ω·cm2, when the coatings with three different thicknesses were immersed in corrosive solution for 240 d. Applying the prediction calculation formula, the relative error was less than 6. 0% between measured and predicted modulus values of low-frequency impedance of the three kinds of coating in the simula-tion solution of coastal chlorine saline soil, C<0. 35, P=1, and the prediction accuracy of the model was good. The life prediction of the solvent-free coal tar epoxy coating with the thickness of 200μm in coastal chloride salt soil simulation was 781 days, and the coating was changed from the initial stage of immersion into the middle stage. With the increase of coating thickness, the coating life was longer, and the predicted life reached 2926 days when the coating thickness was 600μm. Conclusion The corrosion model for life prediction showed good fitting precision and prediction reliability.

By scanning electrochemical microscopy (SECM )and traditional electrochemical method,the effect of loading potential variation on direct methanol fuel cell (DMFC )anode performance was studied. When the anode was loaded for 2 h at different potential,the number of peak current reduced with loading po-tential increasing while the corresponding peak current value increased first and then decreased,which manifes-ted that the anode’s catalytic distributed rather differently and reduced with loaded time and potential.The for-ward and the reverse sweep current peaks in cyclic voltammetry also first moved to negative and then shifted to positive with loaded time increasing while its resistance ability to CO continuously decreased.After loaded for 16 h and 72 h at 0.6 V,the average size of catalysts changed from 3.4 nm to 3.6 nm and 4.4 nm,respectively. While loaded for 72 h at 0.8 V,the weight ratio of Pt/Ru in catalyst changed from 2.0 to 3.9.Changing loaded potential exacerbated the uneven distribution of catalytic site,catalyst particle enlargement and Ru lose,which contributed to the catalytic activity deterioration.

By localized impedance spectroscopy (LEIS) and electrochemical impedance spectroscopy (EIS), the effect of loading potential variation on the performance of direct methanol fuel cell ( DMFC ) anode was studied. During surface scanning, the local impedance of the anode showed sawtooth-like distribution under potential loading, which meant the electrochemical activity in the anode surface was nonuniform. Meanwhile, the local impedance tended to increase with loading potential increasing. After loading 16h and 72h at 0.6V, the average size of catalysts changed from 3.4nm to 3.6nm and 4.4nm, increased by 5.88% and 29.41%. After loaded for 72h under 0.8V, the ratio of Pt:Ru in catalyst changes from 2:1 to 3.9:1. It is the change of the difference in local area, which showed impedance increase, catalyst particle size growing up and agglomeration, the loss of Ru, that contributed to the performance decay of DMFC anode.

为考察无溶剂环氧石油沥青涂层在不同氯离子浓度土壤中的腐蚀行为,采用电化学测试技术测试涂层的腐蚀电位和低频阻抗模值.结果表明,随着土壤中氯离子含量的增加,涂层的腐蚀电位负移,容抗弧半径减小,阻抗模值降低,说明土壤中氯离子含量的增加导致涂层对土壤中腐蚀性介质的屏蔽作用能力有所下降.400 μm厚的涂层在29％ H2O+ 1.8％ NaCl土壤中的交流阻抗谱图呈现单容抗弧特征;随着埋设时间的延长,阻抗模值下降,埋设360d时涂层的低频阻抗模值达8.3020×108 Ω·cm2,涂层未发生鼓泡、裂缝和剥落迹象,表明涂层形成了有效的屏蔽层,对基体金属有着良好的防护作用.

Corrosion behavior of brass coinage was investigated in synthetic sweat solution by electrochemical measurement and surface analysis methods including scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX). It is indicated that chloride ions in sweat solution accelerate the anodic active dissolution of brass, which is the main reason of pitting corrosion and dezincification corrosion. Meanwhile, lactic acid and ammonia water also promote the anode reaction. The corrosion products on the surface are mainly composed of basic copper chloride, cuprous oxide, the complex consisting of urea in association with copper, and few lactate ion. The kinetics of pitting corrosion development obeys the following equation of J0=0.3735(t+185.93)−1/2, and the process is controlled by dissolution of salt deposited on pit surface.

The wear ability and the corrosion resistance of TAMZ alloy implanted by carbon ions were investigated in Hank's body fluid. The results show that the uniformly modified layer formed by implanting carbon ion on TAMZ alloy surface is composed of TiC and Ti with carbon content of 1.07wt%. The thickness of the carbon ions implanted layer is 9 μm. Electrochemical test results indicate that the implanted alloy corrosion potentials and the charge transfer resistance are all increased, and the anodic polarization current density is decreased in Hank's body fluid. This is because the disordered carbide film is formed, which blocks the dissolution of alloying elements. In Hank's body fluid, the friction coefficient and the wear rate of the TAMZ alloy implanted by carbon ions are less than those of TAMZ matrix, but hardness is increased after implantation. In addition, the implanted alloy's anodic polarization current density is decreased and the charge transfer resistance is increased after friction. It means that the modified layer formed by implanting carbon ions has the excellent wear resistance and the corrosion resistance in a simulated human body fluid.

To improve the anode performance of aluminum alloy anode, anode characteristics of Al-Zn-In sacrificial anodes with different Cu impurity content in the seawater were studied by electrochemical method, galvanic corrosion and ICP?MS. The results show that the sacrificial anode has good dissolution morphology by adding 0.005wt.% Cu. Its working potential is between -1.047~-1.068 V, and the current efficiency reaches 93%. The coupling potential is negative and stable and the coupling current is moderate. The dissolved amount of Al and Zn are 22 ppb and 3. 8 ppb at 2 h, and the current peak values of 2 h and 48 h are 27 mA and 36 mA. It means that the anti?corrosion property is enhanced. While the Cu content exceeds 0.005wt.%, with the increasing of Cu content, the resistance of active solution increases gradually, which indicates that the activation of In is limited. The current efficiency of anode decreases obviously. It is found that the aluminum alloy material owns better anode characteristics with 0.005wt.% Cu.

采用电化学测试技术考察无溶剂环氧煤焦沥青涂层在模拟滨海氯盐土溶液中的电化学行为.结果表明,模拟滨海氯盐土溶液中,无溶剂环氧煤焦沥青的开路电位随涂层厚度的增加呈上升趋势,说明涂层厚度的增加提高了侵蚀性溶液的屏蔽阻挡能力.600μm无溶剂环氧煤焦沥青涂层在模拟滨海氯盐土溶液中浸泡30 d内,侵蚀性介质仍没有渗透到涂层-金属基体界面处,交流阻抗谱图显示单容抗弧,阻抗值为8×108Ω·cm2,表明涂层形成了高电阻、低电容的有效屏蔽层,对Q235碳钢基体起到有效的防护作用.

The effects of lanthanum and cerium mixed rare earth metal on the abrasion and corrosion resistance of AM60 magnesium alloy were analyzed by the hydrogen evolution method, mass gain test, electrochemical test, as well as friction and wear characteristics test. It can be found that after adding lanthanum and cerium mixed rare earth metal, AM60 magnesium alloy's electrochemical properties, friction and wear performance are all improved in 0.35%NaCl solution. For example, hydrogen evolution corrosion current density, polarization current density and capacitance all decrease while its corrosion potential and polarization resistance increase. Moreover, its friction coefficient and specific wear rate decrease. This is because adding of lanthanum and cerium results in refining of the grains of alpha phase and Mg17Al12 phase of AM60 magnesium alloy and forming of new Al2Ce and Al11La3 phases, which inhibit the progress of cathodic depolarization, whilst the added Ce and La form a composite anodic film on the surface of the alloy, which block the dissolution and improve the corrosion resistance.

Crevice corrosion behavior of commercial pure titanium (CP Ti), Ti-6Al-4V alloy and Ti-Ni Shape Memory Alloy (SMA) were investigated through an electrochemical methods in Ringer's artificial body fluids. The results indicate that the crevice corrosion occurs for all alloys in Ringer's artificial body fluids at potential of 400 mV. The crevice corrosion for all alloys increases with the increase of corrosion solution temperature. The corrosion potential of Ti-6Al-4V alloy is more positive than that of CP Ti and Ti-Ni SMA, manifesting that the anodic polarization characterization of Ti-6Al-4V is better than those of both CP Ti and Ti-Ni SMA. So its crevice corrosion resistance is enhanced. The dynamic equations of crevice corrosion for CP Ti, Ti-6Al-4V and Ti-Ni SMA are as follows: iT, CPTi=0.028 e−2×10−4t, iT, Ti-6Al-4V =0.0149 e−3×10−4t, iT, Ti-Ni SMA =0.4712 e−7×10−4t, which indicate that the process of the crevice corrosion is controlled by the dissolution of chloride salt film on its surface.

In order to improve the anti-corrosion characteristic of Ag-coated 316SS bipolar plates in PEMFC environment, self-assembled monolayer (SAM) was prepared on its surface by chemical methods. The electrochemical characteristic of modified bipolar plate was also investigated. The results indicated that the SAM was composed of dodecyl thioalcohol. After forming SAM, the bipolar plate’s contact angle increased from 58° to 102°. In addition, its double layer capacitance (Cd) was decreased and charge transfer resistance was increased. The homogeneous SAM, which acted as a protective barrier, inhibited the corrosive ion from corroding. SAM may provide significant protection against corrosion in PEMFC environment.

ABSTRACT:Objective The electrochemical behavior of the solvent-free epoxy coal tar coating was investigated in the soil solution of saturated water content. Methods The solvent-free epoxy coal tar coating was applied on Q235 steel, the open circuit potential and electrochemical impedance spectroscopy of the coatings at different thicknesses and different buried time were tested, and the effects of coating thickness and buried time on the electrochemical behavior of the coating were explored. SEM analysis of the ele-mental composition of corrosion products on the substrate surface were used to explore whether the aggressive substances reached the substrate surface and was involved in the corrosion. Results The stable open circuit potential of Q235 steel with a coating thick-ness of 200μm was about-0. 37 V, and the corrosion potential shifted positively by about 0. 28 V as compared to that of the Q235 bare steel. With the increase of coating thickness, the open circuit potential showed a rising tendency, the capacitance arc radius <br> increased, and the shielded blocking ability of the coating in aggressive solutions was improved. The protective performance of the coating declined, the capacitance arc radius reduced and water absorption increased with the prolonging buried time in soil, but the low-frequency impedance modulus value still reached up to 8. 8×107 Ω·cm2. The energy spectrum analysis showed that no corro-sive substances such as Cl-appeared on the surface of Q235 steel. Conclusion The solvent-free coal tar epoxy coating in soil solu-tion could effectively form a shielding layer and provided an effective protection for Q235 carbon steel.

The inhibition effects of B-Mo-W complex inhibitor on corrosion of mild steel in 55% LiBr solution were investigated using weight-loss method, electrochemistry tests, SEM, EDX, and XRD. The ingredients of B-Mo-W complex inhibitor included organic phosphonic acid B, Na2MoO4, and Na2WO4. The results revealed that B-Mo-W complex inhibitor was capable of inhibiting the corrosion of mild steel in 55% LiBr solution, exhibiting high inhibition efficiencies around 97.7%. B-Mo-W complex inhibitor promoted the formation of a protective passive film composed of Fe, Mo, W, and O elements. The passive film decreased the corrosion rate, improved the electrochemistry performance, and enhanced anti-corrosion ability of mild steel.

Corrosion behavior of brass coinage was investigated in synthetic sweat solution by electrochemical measurement and surface analysis methods including scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX). It is indicated that chloride ions in sweat solution accelerate the anodic active dissolution of brass, which is the main reason of pitting corrosion and dezincification corrosion. Meanwhile, lactic acid and ammonia water also promote the anode reaction. The corrosion products on the surface are mainly composed of basic copper chloride, cuprous oxide, the complex consisting of urea in association with copper, and few lactate ion. The kinetics of pitting corrosion development obeys the following equation of J 0 =0.3735(t+185.93) -1/2 , and the process is controlled by dissolution of salt deposited on pit surface.