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Different types of anion vacancies were optimized in passive films on copper via first-principles calculations based on density functional theory, and numerous potentiodynamic polarizations were performed to evaluate the size matching effect between anion vacancies and halide ions in passive film breakdown on copper. The size of the anion vacancies decreased to some extent compared with the corresponding atom due to the surface relaxation effect, and electrochemical experiments showed that the pitting potential for an oxide passive film on copper followed the order F−

Accelerated corrosion tests of the 7005-T4 aluminum alloy were conducted to determine a suitable service life prediction method by using alternating wet–dry cycles in three kinds of solutions. The morphology and composition analysis of the corrosion product revealed that slight corrosion occurred on the surfaces of the samples immersed in a 0.25wt% Na2S2O8 solution. However, pitting corrosion occurred on the surfaces of the samples immersed in a 3.5wt% NaCl solution, whereas exfoliation corrosion occurred on the surfaces of the samples immersed in a mixture of 0.25wt% Na2S2O8 and 3.5wt% NaCl solutions. A power exponent relationship was observed between the mass loss and exposure time of the 7005-T4 aluminum alloy immersed in the three kinds of solutions. In the mixture of 0.25wt% Na2S2O8 and 3.5wt% NaCl solutions, the mass loss of the aluminum alloy yielded the maximum value. Based on the calculation of the correlation coefficients, the alternating wet–dry procedure in a 3.5wt% NaCl solution could be used to predict the corrosion behavior of 7005-T4 aluminum alloy exposed in the atmosphere of Qingdao, China. The prediction model is as follows: T = 104.28·t0.91, where T is the equivalent time and t is the exposure time.

The correlation between the distribution/size of carbides and corrosion resistance of 17Cr-1Ni ferritic-martensitic stainless steel after different heat treatment temperatures was investigated by transmission electron microscope, electrochemical tests, and corrosion morphology observations. The results showed that the size of the precipitated phase decreased and corrosion resistance increased with an increase in the annealing temperature. When the tempering temperature was low (290 °C), carbides precipitated mainly at the phase boundaries due to a low degree of atomic matching and higher grain boundary energy. In this case, the polarization curve had a passivation interval and the pits were mainly initiated at the phase boundary. When the tempering temperature was higher than 400 °C, the carbides gradually precipitated in the martensite laths because the accelerated diffusion of Cr healed the Cr depletion zone at phase boundary. This outcome resulted in a polarization curve that had no passivation range and uniform corrosion occurred in martensitic region.

Pure copper, tin copper and beryllium copper were exposed to a harsh marine environment, and the effects of tin and beryllium addition on copper corrosion were systematically investigated and compared. The corrosion rate for pure copper was similar with that for tin copper, but significantly higher than that for beryllium copper, indicating an improvement in corrosion resistance due to the addition of beryllium. Pitting corrosion occurred in all investigated materials and the extent of pitting damage was in the order of pure copper > tin copper > beryllium copper. Flaking corrosion was prominent on tin copper plate after long-term exposure and the primary corrosion products in all materials were Cu2O, CuCl and Cu2Cl(OH)3. The tin content in the inner corrosion layer was higher than in the outer layer for tin copper, whereas beryllium accumulated at the outer layer of beryllium copper, confirmed by auger electron spectroscopy, and related corrosion mechanisms were proposed.

Fine gas-atomized powders were prepared for fabricating 316L stainless steel by selective laser melting (SLM) for medical implant applications. The effect of 3D printing laser power on the microstructure, biocompatibility, mechanical and corrosion properties of SLM 316L were systematically investigated and compared with the traditionally quenched. The SLM 316L showed irregular grains with many sub-grains and a thicker passive film with lower Mo content than the quenched 316L. SLM 316L formed at high laser power showed improved elongation, corrosion resistance, and biocompatibility, while that prepared at low power showed poorer performance and was unstable during long-term experiments in simulated body fluid. Keywords: 3D printing, 316L stainless steel, Selective laser melting, Transmission electron microscopy, Corrosion, Bio-compatibility

The effects of chloride concentration, applied potential and time on the passive film of Cu-Zn-Ni ternary alloy in alkaline solution were systematically investigated using potentiodynamic and potentiostatic polarizations, electrochemical impedance spectroscopy, Mott–Schottky analysis, laser confocal microscopy, atomic force microscopy and x-ray photoelectron spectroscopy. Results showed that the pitting potential decreased as a linear function of log( $$ a_{{{\text{Cl}}^{ - } }} $$ ), and the size of pits extended faster in the horizontal direction than in the vertical direction. The passive oxide film formed on Cu-Zn-Ni alloy mainly exhibited p-type semiconductor behavior, which was consistent with cuprous and nickel oxide, the main components in the film. The density of cation vacancy (approximately 1020-1021 cm−3) increased with potentiostatic time but reduced by the increasing potentials. The kinetics of passive film growth followed a parabolic law D = m * tn, where m is a constant considered as the initial growth rate and n is the time exponent. Subsequent to the formation of a compact and coherent passive film at higher potential, it was hard for an ion to migrate or for an aggressive ion to penetrate, which indicated better corrosion resistance for passive film formed under higher potential.

In order to explore the characteristics of soil enzyme activities under different types of plastic film mulching, we set up four different types of plastic film mulching models at Dongyang experimental base of Agricultural Sciences Academy in Shanxi Province in 2016, including common plastic film mulching(P), water-permeable plastic mulching film(SS), biodegradable plastic film mulching(SW), light degradation mulching(G), uncovered film covering in open field(CK) was used as control. The results showed that alkaline phosphatase and nitrate reductase under four kinds of coating treatments were higher than CK in all growth stages, while urease, catalase, and nitrite reductase under plastic film were lower than CK; Soil urease activity was highest in flare opening stage, with CK > G > SW > SS > P; Alkaline phosphatase activity was highest during harvest, SS, SW, P, and G treatments at 0~20 cm soil were 16.17%, 18.97%, 16.34%, and 14.56% highter than CK. The activity of nitrate reductase at 0~20 cm soil of SS, SW, P, and G treatments were 68.57%, 42.86%, 42.86%, and 25.71% higher than that of CK; Combining other factors such as maize yield, we found that the changes of soil alkaline phosphatase activity and nitrate reductase activity were highly significant positively correlated with soil respiration rate and maize yield(P

Microstructure and corrosion behavior of 316L stainless steel fabricated by selective laser melting (SLM) for bipolar plate were investigated and the subsequent heat treatment effect was also clarified. Results showed that sub-grains widely existed in the SLM 316L and the dislocations in the grain boundary migrated and disappeared after heat treatment. The as produced SLM 316L exhibited inferior corrosion resistance than the wrought in 0.5 M H2SO4 solution with 50 ppm Cl− and 2 ppm F− ions at 70 °C due to the SLM defects (molten pool boundaries, non-equilibrium phases etc.), and short, stress relief annealing did not homogenize the non-uniform structures. However, recrystallization heat treatment can improve the durability due to the more uniform structure and thicker passive film. Meanwhile, the proportion of the oxides in passive film formed on SLM 316L increased after heat treatment, especially for the chromic oxide, leading to a better anti-corrosive property.

The evolution of the corrosion process on Cu-Ni-Zn alloy in alkaline chloride solution was investigated by in-situ scanning electrochemical microscopy, X-ray photoelectron spectroscopy, and ex-situ laser confocal microscopy, and the effects of ambient temperature and polarization time were also discussed. The results demonstrated a higher pitting nucleation rate and lower pit growth rate at low temperature. The ratio of pit depth to mouth diameter decreased with increasing pit volume and temperature, indicating that pits preferentially propagate in the horizontal direction rather than the vertical direction owing to the presence of corrosion products and deposited copper. The surface current was uniform and stabilized at approximately 2.2 nA during the passive stage, whereas the current increased after the pits were formed with the maximum approaching 3 nA. Increasing the temperature led to an increase in porous corrosion products (CuO, Zn(OH)2, and Ni(OH)2) and significantly increased the rate of transition from pitting to uniform corrosion. Dezincification corrosion was detected by energy dispersive spectrometry, and a mechanism for pitting transition into uniform corrosion induced by dezincification at the grain boundaries is proposed.

The outer layer nanostructure of stainless steel’s passive film in 0.1 M NaOH has been studied by electrochemical atomic force microscopy and the role of the outer layer in the electrochemical response of stainless steel has been characterized. The outer layer is mainly composed of nanoscale particles whose average diameter is up to 13.14 ± 3.52 nm at the end of the formation period. The formation process is characterized by the nucleation, growth, and contact of oxide particles. Based on the study on the outer layer nanostructure, the gaps/boundaries between particles in the outer layer should be diffusion paths for ions across the layer. The electrochemical impedance spectroscopy analysis revealed that the ion diffusion resistance first increased and then remained stable due to the three-dimensional growth of nanoscale particles.

s In this study, the structure and composition of primary and secondary passive films formed on AM355 martensitic stainless steel were characterized and compared. The film composition analysis revealed that the Fe/Cr ratio in the secondary passive film is significantly lower than that in the metal matrix. Both the primary and secondary passive films are composed of nanoscale particles, and some pores are present in the secondary passive film. Compared to the secondary passive film, the primary passive film exhibits reduced donor density, with a more positive formation potential.

The semiconductor properties and protective role of a single-component Cu2O layer were studied using cyclic voltammetry, Mott–Schottky (MS) tests, electrochemical impedance spectroscopy (EIS), in-situ laser Raman spectroscopy, and electrochemical atomic force microscopy techniques (ECAFM). The results suggest that the single-component Cu2O layer exhibits p-type semiconductor properties. An interesting phenomenon was observed; the carrier concentration, and the diffusivity of the Cu+ vacancies increased progressively as the oxide layer formation potential increased. The oxide layer was composed of granular cuprous oxide; relatively large Cu2O particles were formed on the surface under − 120 mV (Ag/AgCl) and − 60 mV (Ag/AgCl). At a film formation potential of − 120 mV (Ag/AgCl), the thickness of the oxide layer (Cu2O) was approximately 6.046 nm, while it was 0.5594 nm at 0 mV (Ag/AgCl). The Cu2O layer formed at a lower potential offers superior stability and protection.

In this study, the 5-Amino-1,3,4-thiadiazole-2-thiol grafted graphene oxide (AMT-GO) composite was synthesized and the corrosion protection properties of the neat EP, GO/EP and AMT-GO/EP coatings at the ambient and low temperatures were comparatively studied. Based on the experimental results, AMT is anchored on GO mainly via the reactions between -NH2 and -SH of AMT and -COOH and -CH(O)CH- of GO. After modification, the dispersity of the GO nanosheets is significantly improved. As the filler, both of the GO and AMT-GO nano-platforms could enhance the protective ability of the polymer coating, the latter possessing the more remarkable effect because of its better dispersity and the beneficial impact provided by exposed -NH2 and -SH. All of the three coatings exhibit worse anti-corrosion performance at the low temperature than the ambient temperature, because the diffusion of corrosive media across the polymer matrix and along the substrate/coating interface could be accelerated by freezing.

The semiconducting properties of passive films formed on copper, in anaerobic alkaline sodium chloride solution, were studied using Mott–Schottky analysis and electrochemical impedance spectroscopy, based on the point defect model. Results showed that the corrosion resistance increased with increasing potential, which was attributed to a well crystallised, refined grain structure, and a thicker passive film at higher potential. P-type semiconducting characteristics were obtained with or without chloride. The density of copper vacancies was approximately 1020 cm−3, and increased with the increasing chloride concentration, which was attributed to faster film-formation in a higher chloride environment. The diffusion coefficient of the defects, a key dynamic parameter for passive film breakdown, was in the range of 10−16–10−15 cm2 s−1, and increased with increasing chloride concentration, thus leading to a greater probability of pitting.

In situ atomic force microscopy, scanning Kelvin probe force microscopy, and potential pulse technology were used to study the pitting behavior induced by inclusions in AM355 martensitic stainless steel. The MnS-(Cr, Mn, Al)O duplex inclusion exhibited the highest sensitivity to the pitting corrosion with respect to the individual MnS and (Cr, Mn, Al)O inclusions. When exposed to a solution containing Cl−, the selective dissolution occurred on the sulfide segment of the duplex inclusion, leading to trenching along the oxide part. The dissolution mechanism of MnS segment in the duplex inclusion is similar to the individual MnS inclusion. The Cr depletion in the boundary layer at the inclusion/metal interface promoted the transition from metastable to stable pitting corrosion in the duplex inclusion.

Influence of temperature on the electrochemical and passivation behavior of 2507 super duplex stainless steel in the simulated desulfurized flue gas condensates in thermal power plant chimney are investigated. Cathodic reactions are enhanced with temperature, accompanying with the involvement of oxygen reduction when the temperature is raised to 60 °C or higher. The unchanged semiconductor type, enrichment of Cr and thickening of the passive film are observed as the temperature increases. The temperature-induced variations of film structure and doping concentrations are responsible for the degradation of protective ability of the passive film.