In order to mitigate the corrosion of steel rebar in concrete, a new environmentally friendly corrosion inhibitor formula (WKI) was designed and the corrosion inhibitive effects of WKI on steel rebar were studied by gravimetric method, electrochemical impendence spectroscopy (EIS), potentiodynamic polarization and Mott–Schottky scanning in simulated concrete pore solution. Furthermore, surface analysis and quantum chemical calculations were conducted in order to illustrate the corrosion inhibitive mechanism. The results indicate that WKI exhibits excellent corrosion inhibitive activities on steel rebar in simulated concrete pore solution. By the presence of WKI, local corrosion was significantly suppressed and no pitting could be detected during the whole experimental period. The total corrosion resistance was increased from 5469 Ω cm² to 64 440 Ω cm² and the corrosion current density was reduced from 3.23 μA cm⁻² to 0.21 μA cm⁻² for the sample immersed in the corrosion medium for 7 d with WKI. The corrosion potential of the steel rebar electrode moved to a higher level and the charge transfer resistance increased, indicating that the anti-corrosion properties of the steel rebar were enhanced. The corrosion inhibitive mechanism of WKI can be attributed to the fact that it can promote the formation of a passive film and reduce its defect concentration via its adsorption and interaction with the metal surface, consequently inhibiting the corrosion of steel rebar caused by chloride ions.

An extract of cucumber leaves (ECSL) was prepared as a green corrosion inhibitor for carbon steel. Its carbon steel corrosion inhibition performance against 0.5 mol L⁻¹ H₂SO₄ was investigated using electrochemical methods and scanning electron microscopy (SEM). Its composition was analyzed by gas chromatography and mass spectroscopy (GC−MS). Quantum chemical calculations and molecular dynamics simulations (MDS) were conducted to elucidate the adsorption mechanism of the inhibitor molecules on the carbon steel surface. The results indicated that the inhibition efficiency increases with its increasing concentration. The extract acted as a mixed type corrosion inhibitor, and its inhibition properties were ascribed to the geometric coverage effect induced by its adsorption on the metal surface in accordance with Langmuir’s law. The active components in the extract were identified as mainly organic compounds with functional groups such as aromatic moieties and heteroatoms. The inhibition activities of ECSL are delivered through the ability of the active components to adsorb on the metal surface through their functional groups to form a protective layer which hinders the contact of aggressive substances with carbon steel and thus suppresses its corrosion. This research provides an important reference for the design of green corrosion inhibitors based on plant waste materials.

Glucosamine is a natural drug widely used for treating osteoarthritis and is usually left until it expires, which will cause a waste of resources if treated as garbage. However, its molecule contains many heteroatoms, entitling it to be a potential corrosion inhibitor. In this investigation, the corrosion inhibition activities of two types of expired glucosamine drugs (glucosamine hydrochloride and glucosamine sulfate) on carbon steel were estimated by electrochemical methods in the acidic solution. The results demonstrated that the glucosamine drugs were mixed-type corrosion inhibitors. Glucosamine hydrochloride could inhibit the carbon steel corrosion more significantly than that of sulfuric style at the same glucosamine content, suggesting a possible synergistic effect of glucosamine molecules with halide ions. Then, the co-adsorption behaviors of glucosamine sulfate with iodide ions were studied by experimental research, as well as theoretical investigations. The results indicated that the inhibition effect could be significantly enhanced when the glucosamine drug was utilized in combination with iodide ions. The electronic structures played a critical role in the synergistic inhibition of glucosamine drugs and iodide ions. Neutral molecules could interact with the metallic surface vertically through the amino and carbonyl groups, while protonated molecules were able to adsorb on it in parallel with the help of multiple functional groups. Since glucosamine molecules would be protonated and positively charged in the acidic solution, they were difficult to adsorb on the solid surface with metallic cations. When the iodide ions were presented, they preferentially adsorbed on the carbon steel surface and induced it to be negatively charged. Therefore, protonated glucosamine molecules could adsorb on the metallic surface using iodide ions as a bridge and form a protective film to mitigate the carbon steel corrosion.

A series of Zr-TiO₂ catalysts were prepared using a facile sol-gel method and were used for N-methylmorpholine (NMM) oxidation to N-methylmorpholine-N-oxide (NMMO). The structure features of Zr-TiO₂ catalysts were studied in detail through a variety of characterization methods, such as XRD, SEM, N₂ adsorption-desorption isotherms, XPS, EPR, and O₂-TPD. As-obtained 5%Zr-TiO₂ catalysts had superior catalytic performance and stability with a 97.6% NMMO yield at 40 °C, which related to Zr doping, a higher surface area, more oxygen vacancies, and oxygen chemisorption on the catalytic surface. This work provides an efficient preparation strategy of TiO₂-based catalysts for selective oxidation reactions by a facile method.