Green corrosion inhibitors are promoted as sustainable substitutes for toxic or persistent additives, yet high short-term inhibition efficiency is not sufficient evidence of practical readiness. This critical review examines plant extracts, agro-industrial residues, amino acids, biopolymers, ionic liquids, deep eutectic solvents, nanoparticles, protective coatings and hybrid formulations as evidence-graded corrosion-control systems. The analysis links molecular identity, interfacial adsorption, electrochemical response, surface confirmation, microstructure, passive-film stability, toxicity, biodegradability, reproducibility and industrial qualification. Recent studies show that high efficiencies can be reached under optimized laboratory conditions when donor atoms, pi-electron density, amphiphilic organization, polymeric films, multilayer architectures or nanoparticle-assisted blocking promote surface protection. However, persistent limitations remain: poorly defined extract composition, weak batch control, short exposure windows, incomplete impedance fitting, overinterpreted quantum-chemical descriptors, scarce ecotoxicity or flow-loop validation, and limited integration with materials-engineering constraints. The review therefore proposes a qualification framework that judges green inhibitors by convergence among chemistry, electrochemistry, surface evidence, environmental compatibility, microstructural context and operational readiness rather than by inhibition efficiency alone.
In this research, two novel tri-cationic surfactant derivatives were synthesized, stemming from vanillin – a compound employed as a sweetener in the food and beverage industry, a flavoring agent in perfumery, and an odor masking substance in cleaning products and animal feed. The structural characteristics of these synthesized compounds were unequivocally confirmed by FT-IR, 1H NMR, and 13C NMR spectroscopic analyses. Furthermore, their efficacy in inhibiting the corrosion of St37 steel was systematically evaluated by integrating gravimetric (weight-loss) measurements with complementary electrochemical techniques. For the corrosion experiments, 1 M HCl was selected as the corrosive medium, and solutions were prepared with inhibitor concentrations set at 1, 5, 10, 50, and 100 ppm. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements were conducted during the electrochemical tests to ascertain the performance of the prepared inhibitors. High inhibition efficiency values, reaching up to 98.7 %, were obtained at the optimum inhibitor concentration of 100 ppm. The adsorption behavior was observed to be consistent with the Langmuir isotherm model. Additionally, theoretical calculations (DFT) were utilized to explore the correlation between the molecular structure of the inhibitors and their corrosion inhibition effectiveness. The results unequivocally demonstrate that these two newly synthesized vanillin derivative tri-cationic surfactants function as highly effective corrosion inhibitors for St37 steel within a 1 M HCl solution.
A structurally stable Zn-MoS2-TiO2 nanocomposite was successfully produced by wet-impregnation doping and a hexane-assisted TiCl4 sol-gel technique. In this present research work, a novel methodology of hexane-assisted sol-gel synthesis with precise control of reaction parameters was adopted, which helped in maintaining the stability of the anatase TiO2 structure while improving its surface and interfacial characteristics for lubrication applications. XRD analysis confirmed that the anatase phase was maintained after Zn and MoS2 inclusion, with an average crystallite size of 15-16 nm. The appearance of the characteristic MoS2 (002) peak at 14.23 degrees verified the successful integration of stacked MoS2 nanosheets without structural degradation. Consistent element distribution was confirmed by EDS analysis, and a nanoflower-like morphology was revealed by SEM. While the layered structure of MoS2 introduced controlled heterogeneity, DLS-zeta analysis showed enhanced dispersion stability after Zn doping (PDI < 0.3). UV-DRS analysis revealed that the absorption edges for Zn-TiO2 and TiO2 were approximately 380 nm and 390 nm, respectively. This nanocomposite's dual absorption properties (similar to 380 nm and similar to 600 nm) indicated the existence of strong interfacial electronic interactions. FTIR spectra confirmed the successful surface modification and revealed the presence of Mo-S and Ti-O bonds. All things considered, a clear structure-property relationship is demonstrated by the combination of improved dispersion behaviour, structural stability, and interfacial electronic modulation. These physicochemical improvements suggest the material's suitability for lubrication-related applications.
This study couples transient ISO 11997-1 cyclic salt-spray modelling with laboratory tests to assess galvanic corrosion of bolted A4 stainless-steel/EN AW-6082 assemblies. A time-dependent electrolyte-film thickness and conductivity model was coupled to a galvanic-corrosion solver to quantify how washer electrochemistry and geometry affect galvanic currents and corresponding mass loss. Washer open-circuit potential E-corr and exchange current density i(0) are primary controls: more noble washers or higher i(0) drive larger cathodic currents, especially in thin films. Design should keep the aluminium potential below the pitting potential E-pit via low-activity or insulating washers, geometric adjustments, or insulating/coating treatments. Simulations show nylon washers reduce predicted mass loss by approximate to 65 %, with a further approximate to 32 % reduction when washer diameter is increased by 8 mm. Geometry optimisation can reduce currents and mass loss up to threefold.
Coating technologies play a crucial role in protecting ship components exposed to seawater from corrosion. Oxide coatings produced by thermal spraying are widely used for corrosion protection; however, their mechanical toughness is often insufficient. Tungsten carbide (WC) coatings, known for excellent toughness, gain industry attention. This study prepared them via atmospheric plasma spraying (APS) and high-velocity oxygen fuel (HVOF) spraying, comparing with Al2O3-40 % TiO2 coatings on tin bronze substrates. The fracture toughness of APS-sprayed oxide and WC-based coatings was 1.10 and 1.37 MPa m(1/2), respectively, whereas that of the HVOF-sprayed WC-based coating reached 3.83 MPa m(1/2). The HVOF-sprayed coatings exhibited significantly fewer pores and microcracks than those produced by APS. In salt spray corrosion tests conducted for 10 and 20 days, the HVOF-sprayed WC-based coating showed the best corrosion resistance, followed by the APS-sprayed oxide coating, while the APS-sprayed WC-based coating exhibited the poorest performance. Microstructural observations and energy-dispersive spectroscopy analyses indicate that the dense microstructure of the HVOF-sprayed WC-based coating effectively inhibited the penetration of corrosive media during salt spray exposure, which is directly related to its superior coating quality.
