Titanium dioxide (TiO2) nanotube arrays coupled with a narrow gap semiconductor—bismuth selenide (Bi2Se3)—exhibited remarkable enhancement in the photocathodic protection property for 304 stainless steel under visible light. Bi2Se3/TiO2 nanocomposites were successfully synthesized using a simple two-step method, including an electrochemical anodization method for preparing pure TiO2 and a chemical bath deposition method for synthesizing Bi2Se3 nanoflowers. The morphology and structure of the composite films were studied by scanning electron microscopy, energy dispersion spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. In addition, the influence of the Bi2Se3 content on the photoelectrochemical and photocathodic protection properties of the composite films was also studied. The photocurrent density of the Bi2Se3/TiO2 nanocomposites was significantly higher than that of pure TiO2 under visible light. The sensitizer Bi2Se3 enhanced the efficient separation of the photogenerated electron-hole pairs and the photocathodic protection properties of TiO2. Under visible light illumination, Bi2Se3/TiO2 nanocomposites synthesized by the chemical bath deposition method with Bi3+ (0.5 mmol/L) exhibited the optimal photogenerated cathodic protection performance for 304 stainless steel.

In this work, the morphology, chemical constitution, and pH sensing performance of IrO _x electrode prepared by cyclic voltammetry (hydrous) and thermal oxidation (anhydrous) are investigated. The results suggest that, IrO _x film prepared by the electrochemical method consists of Ir(III) and Ir(IV). A hydration treatment of 30 days is required to establish a super-Nernstian response to pH (67 mV/pH). IrO _x film prepared by thermal oxidation has a stronger adhesion with the substrate and consists of Ir(III), Ir(IV) and Ir(VI). A more thorough hydration of 60 days is required to establish a Nernstian response to pH (59 mV/pH). The pH sensing mechanism of both electrodes is discussed and their respective application field is recommended.

This work studied the application of phosphoric acid-gallic acid in vinyl chloride acrylic emulsion and its rust conversion performance. The increase of phosphoric acid affected the stability of the system, leading to the rapid precipitation of flocculent precipitation. Rust conversion coating (RCC) showed the best synergistic conversion effect when gallic acid (GA) was 0.2 wt.% and phosphoric acid (PA) was 2 wt.%. XRD and FTIR analysis show that the components of adherent rust (AR) are α-FeOOH, γ-FeOOH and Fe₃O₄. The conversion products are ferric phosphate (FP) and ferric gallate (FG). The RCC can effectively treat the rusted steel (RS) produced by simulated marine atmospheric corrosion. The corrosion current density was reduced by three orders of magnitude, the adhesion reached 2.75 MPa, and the salt spray corrosion resistance was 20 days. The results of Raman, XPS, SEM and EDS show that the ionic dissolution of iron, complexation and further oxidation reactions occur at the interface between the adherent rust and the RCC. After rust conversion treatment, unreacted rust (UR) affects the further improvement of adhesion strength and anti-corrosion performance.

In this study, the galvanic corrosion behavior of Cu and CS (carbon steel) in simulated Beishan groundwater was investigated. The influence of Cu:CS area ratio (up to 8000), temperature (20–70 °C), O ₂ content (groundwater sparged with air, N ₂ , and in a N ₂ -filled glove box), on galvanic current density ( i _g ) was investigated. In the presence of sufficient O ₂ , the slope of steady-state galvanic current density ( i _g ^∞ ) to Cu:CS area ratio indicates the segmented control process of galvanic corrosion, which are O ₂ reduction kinetic control, O ₂ diffusion control, and anodic reaction control. As Cu:CS area ratio increases, i _g ^∞ plateaus show up, revealing the most intense galvanic corrosion situation. As the O₂ content decreases, the Cu:CS area ratio at which the i _g ^∞ plateau appears decreases. In addition, it was found that in the presence of O ₂ , Cu, as the cathode of the galvanic couple, undergoes anodic dissolution. The dissolution of Cu ⁺ was confirmed by complexing it with bathocuproine disulfonate disodium (BCS). The oxidation of Cu ⁺ to Cu ²⁺ in solution was confirmed by ICP-MS analysis.