[en] A 3-dimensional ZnIn₂S₄/TiO₂ nanotubes composite was prepared by a combined hydrothermal reaction and electrochemical anodization method. Photogenerated open circuit potential, photogenerated current density, electrochemical impedance spectra, Tafel curves, and i-V curves were measured to investigate the photoelectrochemical activities and photocathodic protection properties for Q235 carbon steel. The results showed that the photocurrent density of the ZnIn₂S₄/TiO₂ composite was greatly increased compared with pure TiO₂. Under visible light irradiation, the photocurrent density of the ZnIn₂S₄-0.25/TiO₂ composite can reach 400 μA cm⁻², which was two times that of TiO₂. The photogenerated potential drop of the composite photoanode was about 0.36 V, which was greater than that of TiO₂ (about 0.16 V). The introduction of the ZnIn₂S₄ improved the visible light absorption ability and photogenerated charge separation efficiency of TiO₂. The loading of ZnIn₂S₄ onto the TiO₂ surface led to a negative shift of the Fermi level of TiO₂. The generation of adsorbed oxygen can facilitate the separation of photogenerated charges.

[en] The oxo-triazole derivative (DTP) was synthesized and its inhibiting action on the corrosion of mild steel in sulphuric acid was investigated by means of weight loss, potentiodynamic polarization, EIS and SEM. The results revealed that DTP was an excellent inhibitor and the inhibition efficiencies obtained from weight loss experiment and electrochemical experiment were in good agreement. Potentiodynamic polarization studies clearly revealed that DTP acted essentially as the mixed-type inhibitor. Thermodynamic and kinetic parameters were obtained from weight loss of the different experimental temperatures, which suggested that at different temperatures (298-333 K) the adsorption of DTP on metal surface obeyed Langmuir adsorption isotherm model.

[en] The microstructure and electrochemical behaviors of Mg-Al-Zn and Mg-Al-Zn-Ga alloys as anode materials were investigated by morphology observation, composition analysis, phase identification, and electrochemical tests. The experimental results suggest that Ga alloying can refine the grains of the Mg-Al-Zn alloy by promoting second-phase segregation, which comprises Mg₁₇Al₁₂ and GaMg₂. The comparison of discharge tests indicates that adding Ga to the Mg-Al-Zn alloy can negatively shift the discharge potential, provide a high current density, promote the formation of tiny and thin products, and improve the utilization efficiency. Meanwhile, the addition of Ga can increase the corrosion resistance of Mg-Al-Zn alloy because the Ga alloying promotes the segregation of the intermetallic phases in the Mg matrix. The intermetallic phases disperse in isolate states in the Mg matrix, resulting in their falling off from the substrate once their adjacent Mg is exhausted and subsequently ceasing the micro-galvanic corrosion. The Mg-Al-Zn-Ga alloy with higher corrosion resistance performs better discharge activity than that of Mg-Al-Zn alloy in 3.5 wt.% NaCl solution, implying that the Mg-Al-Zn-Ga alloy is a promising anode material for seawater-activated battery.

[en] Highlights: ► Tannic acid has good inhibition effect for mild steel in wet/dry conditions. ► Significant difference in rust appearance is observed by means of SEM. ► Tannic acid acts as a cathodic-type inhibitor. ► The XRD and FT-IR analyses support the weight loss, EIS, and polarisation data. -- Abstract: The inhibition effect of tannic acid on mild steel corrosion in seawater wet/dry cyclic conditions was studied by weight loss and electrochemical methods. Result of the polarisation curves shows that corrosion current density decreases from 47.85 μA cm⁻² to 6.67 μA cm⁻² after tannic acid is added; charge transfer resistance remains stable in the electrochemical impedance spectra. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared reflection are performed to study the corrosion inhibition. The inhibition effect of the compound is attributed to ferric tannate film formation on the steel surface, which is relatively stable during wet/dry cycles

[en] It has been found that microbial communities play a significant role in the corrosion process of steels exposed in aquatic and soil environments. Biomineralization influenced by microorganisms is believed to be responsible for the formation of corrosion products via complicated pathways of electron transfer between microbial cells and the metal. In this study, sulfide corrosion products were investigated for 316L stainless steel exposed to media with sulfate-reducing bacteria media for 7 weeks. The species of inorganic and organic sulfides in the passive film on the stainless steel were observed by epifluorescence microscope, environmental scanning electron microscope combined with energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The transformation from metal oxides to metal sulfides influenced by sulfate-reducing bacteria is emphasized in this paper

[en] Three triazole derivatives (4-chloro-acetophenone-O-1'-(1',3',4'-triazolyl)-metheneoxime (CATM), 4-methoxyl-acetophenone-O-1'-(1',3',4'-triazolyl)-metheneoxime (MATM) and 4-fluoro-acetophenone-O-1'-(1',3',4'-triazolyl)-metheneoxime (FATM)) have been synthesized as new inhibitors for the corrosion of mild steel in acid media. The inhibition efficiencies of these inhibitors were evaluated by means of weight loss and electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and polarization curves. Then the surface morphology was studied by scanning electron microscopy (SEM). The adsorption of triazole derivatives is found to obey Langmuir adsorption isotherm, and the thermodynamic parameters were determined and discussed. The relationship between molecular structure of these compounds and their inhibition efficiency has been investigated by ab initio quantum chemical calculations. The electronic properties such as the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) energy levels, energy gap (LUMO-HOMO), dipole moment and molecular orbital densities were computed

[en] CdTe/graphene/TiO_2 films that served as photoanodes for cathodic protection application were prepared by an electrochemical deposition method. The deposition of graphene and CdTe nanoparticles (NPs) on the surface of the TiO_2 nanotubes was confirmed by scanning electron microscope and transmission electron microscopy. The composites exhibited high light absorption in both the UV and visible light region. The results indicated that TiO_2 nanotube photoelectrodes sensitized by 20-cycle graphene and 30-cycle CdTe NPs exhibited effective photocathodic protection properties for 304 stainless steel (304SS) under the visible-light illumination, with an photopotential of −750 mV versus saturated calomel electrode and a current density of 560 μA cm"−"2. Due to the efficient photogenerated charge separation, the three-component CdTe/graphene/TiO_2 showed stronger photoresponse than pure TiO_2 under visible-light illumination. In summary, the CdTe/graphene could improve the photocathodic protection properties of TiO_2 films. (paper)

[en] Highlights: • Hydrothermal method for synthesizing ZnFe₂O₄ nanoparticles on TiO₂ NTs. • The photoelectrochemical property of TiO₂ could greatly improve by doping ZnFe₂O₄. • The ZnFe₂O₄/TiO₂ composite films provide a better photocathodic protection for 304SS. - Abstract: ZnFe₂O₄ sensitized TiO₂ nanotubes were fabricated via anodic oxidation and hydrothermal method. The ZnFe₂O₄/TiO₂ composite films with different concentrations were synthesized to explore the optimal photoelectrochemical property compared with pure TiO₂ nanotubes. The morphology and chemical composition of samples were characterized by scanning electron microscopy, energy-dispersive spectrometry, and X-ray diffraction. The performance of protection for 304 stainless steel was investigated by electrochemical tests, such as open circuit potential and photocurrent density. The results indicate that ZnFe₂O₄/TiO₂ composite films showed efficient photocathodic protection effect for 304 stainless steel under visible light, and the optimal specimen composite films shifted the corrosion potential of 304 stainless steel to −780 mV.

[en] For improving the photocathodic protection performance of TiO₂ photoanode, ZnIn₂S₄/reduced graphene oxide (RGO)/TiO₂ nanotubes (NTs) composite was synthesized by electrochemical anodizing combined with hydrothermal method. The photoelectrochemical and photocathodic protection properties of the ZnIn₂S₄/RGO/TiO₂ composite were investigated in detail. Compared with pure TiO₂ NTs, the ZnIn₂S₄/RGO/TiO₂ composite showed a significant improvement in photocathodic protection performances. The photogenerated open circuit potential drop of ZnIn₂S₄/RGO/TiO₂ coupled with Q235 carbon steel in 3.5 wt% NaCl solution under visible light could reach 420 mV versus saturated calomel electrode, which was more than twice as much as that of pure TiO₂. The photogenerated current density of ZnIn₂S₄/RGO/TiO₂ could reach 5.6 mA cm⁻², which was twice as much as that of pure TiO₂. The appearance of the adsorbed oxygen (O_A) enabled the ZnIn₂S₄/RGO/TiO₂ to have better photo-carrier separation efficiency and better photogenerated cathodic protection than pure TiO₂. The present work demonstrated ZnIn₂S₄/RGO/TiO₂ could be a potential material for photoanodes because of its better visible-light response, higher electrical conductivity and smaller charge transfer resistance. (paper)

[en] ZnWO₄/TiO₂ composite films were fabricated on TiO₂ substrate by hydrothermal method. The ZnWO₄ nanorods-sensitized TiO₂ coupled with 304 stainless steel was served as photoelectrode to study its anticorrosion effect for metal. Under visible light, the photocathodic protection ability of TiO₂ and ZnWO₄/TiO₂ composite film was measured by photoelectrochemical program on potentiostat. Open circuit potential variation result showed that sanmartinite ZnWO₄ nanorods could enhance the photoelectrochemical activity of TiO₂, and the ZnWO₄/TiO₂ composite films could absorb energy and store electrons to play a role in corrosion protection for metal. (paper)