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.
This study aimed to develop an environmentally friendly corrosion inhibitor derived from okra extract to mitigate corrosion damage of mild steel in 1 M hydrochloric acid (HCl) solution. The optimal concentration of the extract was determined through weight loss and electrochemical measurements. Scanning electron microscopy was applied to characterize the surface morphology of specimens before and after corrosion behavior. The results indicated that mild steel underwent severe corrosion in 1 M HCl, which was significantly inhibited after the addition of okra extract. The inhibition efficiency increased with higher concentrations of the extract, exceeding 90 % at 8,000 mg/L. The adsorption behavior of inhibitor followed the Langmuir isotherm and was determined to be physical type. Fourier transform infrared spectroscopy (FT-IR) was conducted and found O-H, C-H, C=O, C=C and C-O bonds are abundant in okra extract, which has significant meaning on the adsorption of okra extract molecules onto the substrate. Furthermore, theoretical quantum chemical calculations were employed to elucidate the corrosion inhibition mechanism, revealing that glucose and rhamnose components in the extract contribute effectively to the corrosion protection of mild steel in HCl solution.
This study investigated the kinetics and mechanisms of high-temperature corrosion of common aerospace alloys, such as those used in aircraft engines and fuselage skins, when locally exposed to the fire extinguishing agent C 2 F 5 I.The aim is to elucidate the material degradation process and to assess the efficacy of C 2 F 5 I as a halon replacement in aerospace applications. The results of the study showed that at 200 °C, C 2 F 5 I was compatible with all metals tested with no significant corrosion. However, at temperatures above 300 °C, the thermal decomposition of C 2 F 5 I produced C1–C4 fluorinated hydrocarbon products that resulted in significant corrosion of the alloys. Among these alloys, 2024 exhibits the best corrosion resistance, which shows that the performance of Al-based alloys is better than that of Fe-based alloys and Cu-based alloys. Based on these findings, the most heavily corroded alloy, H62, was selected for further analysis of corrosion products and gas by-products. The mechanism of Cu alloy corrosion by C 2 F 5 I at elevated temperatures was elucidated. The results provide valuable insights for performance evaluation and selection of halon alternatives.
The atmospheric corrosion behavior of 60Si2MnA spring steel was investigated in environments containing chloride (Cl − ) and sulfate (SO 4 2− ). Bare steel specimens were exposed to controlled laboratory conditions that replicated key parameters of the target atmosphere. The deliquescence and weathering characteristics of the deposited salts were examined using electrochemical impedance spectroscopy, while a custom-built salt deposition system was employed to conduct corrosion tests at constant temperature and humidity (20 °C/75 % RH and 40 °C/75 % RH) with a surface salt load of 10 g/m 2 over varying exposure durations. Pronounced corrosion was observed under both temperature conditions. X-ray diffraction and Raman spectroscopy revealed that the corrosion products were primarily composed of iron oxyhydroxides and iron oxides. Scanning electron microscopy combined with electrochemical analyses showed that, at early exposure stages, the rust layer exhibited abundant cracks and pores, allowing for the ingress of corrosive species. The initial corrosion products acted as strong oxidants, enhancing cathodic reactions and thus accelerating metal degradation. With increasing exposure time, the thickening of the rust layer provided partial protection, slightly improving the corrosion resistance. Elevated temperature was found to significantly accelerate both the corrosion rate and the evolution of corrosion products.
This review paper explores the ongoing challenge of internal corrosion in oil and gas pipelines, specifically focusing on the damage caused by hydrogen sulfide (H 2 S). It highlights the superior performance of coating technologies such as chemical resistance, long-term durability, and resistance to high temperatures, including epoxy and other nonmetallic coatings, which effectively protect pipelines against H 2 S-induced corrosion. The review covers the practical application of coating technologies to improve pipeline durability and operational efficiency, beginning with an examination of the corrosive impact of H 2 S on pipelines. It reviews existing mitigation strategies, highlighting their advantages and limitations, and then analyzes nonmetallic coatings as a promising solution to H 2 S-induced corrosion. The paper demonstrates the benefits of these advanced coatings. It concludes with a summary of key findings and provides industry recommendations for selecting and implementing effective coating technologies, alongside suggestions for future research in this field.
Deep learning (DL) techniques are advancing quickly, which has increased interest in leveraging them to analyze intricate corrosion patterns and forecast corrosion behavior. This offers a huge challenge across multiple industries, resulting in large financial losses and safety risks. It results in the creation of solutions that are more accurate, effective, and proactive to tackle corrosion-related challenges, thereby enhancing the safety, reliability, and sustainability of vital infrastructure systems. This review commences by utilizing deep learning algorithms and its applications in corrosion assessment across various sectors, encompassing corrosion detection, prediction, classification, and material degradation analysis. The goal is to offer insights in current status and future prospects of corrosion management.
Corrosion of reinforcing steel remains one of the most pressing durability challenges for concrete infrastructure, with substantial economic and safety implications. This review provides a systematic and critical synthesis of research on hot-dip galvanized (HDG) reinforcement, integrating electrochemical, structural, and field-based perspectives. The methodology involved comparative evaluation of laboratory studies, long-term monitoring data, and technological advances to identify consensus findings and unresolved controversies. The novelty of this review lies in its focused analysis of three critical debates: the influence of initial hydrogen evolution on interfacial bond strength, the conditional stability of the calcium hydroxyzincate passive layer in high-alkalinity environments, and the discrepancy between accelerated laboratory testing and field performance. The review also compares HDG with alternative reinforcement systems, particularly epoxy-coated and stainless steel rebars, to contextualize durability and cost trade-offs. Recent innovations, including continuous galvanized rebar (CGR), zinc-alloy modifications, non-destructive evaluation methods, and computational service-life modeling, are highlighted as transformative developments. By systematically bridging mechanistic insights with practical outcomes, this review advances current understanding of galvanized reinforcement and identifies critical directions for future research aimed at reliable service life prediction and optimized application in durable concrete structures.
As the critical first step in structural health management and fault diagnosis, corrosion monitoring is inherently multidisciplinary in nature. While conventional in situ techniques capture real-time electrical, vibrational, and thermal signatures, their effectiveness is constrained by limited detection precision, inefficient data analysis, and unreliable predictive modeling. The convergence of artificial intelligence (AI) and big data analytics has fundamentally transformed this field, generating considerable academic interest over the past decade. Machine learning (ML) – serving as the cornerstone of this revolution – excels not only in extracting nonlinear features from nonstationary processes but also employs probabilistic inference frameworks to quantify predictive uncertainty, thereby substantially augmenting in situ monitoring capabilities. This review systematically examines advancements in ML-assisted corrosion monitoring throughout the preceding decade, categorizing prevalent algorithms according to domain-specific implementations while evaluating enhanced in situ techniques through empirical case studies demonstrating superior data processing efficacy. Finally, we project future trajectories for intelligent monitoring technology in light of persistent challenges and emergent innovations.
Atmospheric chloride deposition rate is the important factor in atmospheric corrosion. However, current research on the distribution of atmospheric chloride deposition in coastal region of China is limited, hindering accurate quantitative analysis of its corrosion effect. We conducted environment monitoring, deposition rate measurement, and metals exposure experiments in coastal region of Hainan Province, China. By analyzing the holistic process of atmospheric chloride, we proposed a deposition rate estimation model considering production, transportation, and deposition (PTD) processes. The proposed PTD regression model significantly improves estimation accuracy and generalizability, achieving an R2 of 0.88 on the measured dataset. Additionally, based on environmental exposure experiments, we developed a metal corrosion loss assessment model for coastal region, well-validated on the four metals tested, with all R2 values exceeding 0.92. Using these models, we constructed spatial and temporal distribution maps of atmospheric chloride deposition rate and its corrosion effects in coastal region of Hainan Province, China, providing guidance for the corrosion assessment, protection, and maintenance of metal products.
Traditional neutral salt spray tests fail to accurately simulate the accelerated corrosion that occurs under actual energized conditions. We have developed a salt spray test chamber capable of reducing the relative humidity (RH) in the testing environment to prevent short circuits, insulation failures, and other faults that lead to premature damage during testing. Initially, the effect of salt spray concentration on corrosion at 85 % RH was examined, and it was found that the corrosion rate does not increase when the concentration surpasses 50 mg/m 3 . The humidity-controllable salt spray test demonstrated a closer match to real environmental corrosion, judging by both the appearance of corrosion and the acceleration ratios across different metals, where the acceleration ratio difference between maximum and minimum values was reduced from 18.6 times to 1.4 times. The influence of RH on the corrosion rate was revealed, with the highest rate observed at 75 % RH. Lastly, we proposed optimal parameters for energized salt spray tests, evaluated the failure modes of several products under these tests, preliminarily confirmed the consistency and acceleration effects of this method for electrical products in real marine atmospheric conditions.
Gravimetric tests are widely used to evaluate the effectiveness of corrosion inhibitors in pipelines and equipment. However, there is always some measurement error due to the more intense corrosion damage to the edges of the samples, and the smaller the sample size, the greater this error will be. The developed method involves testing coupons of different sizes under the same conditions, and then mathematically calculating excess weight loss along the edges of the coupon. In the experiment conducted by the authors, when testing samples in an aggressive environment without an inhibitor, the measured corrosion rate turned out to be 9 % higher than the real one. Similarly, in an environment with an imidazoline inhibitor, the corrosion rate turned out to be 15 % higher than the real one, taking into account the edge effect. The application of the method of accounting for the excessive corrosion rate of the coupon edge will increase the accuracy of gravimetric measurements and increase the accuracy of predicting the timing of structural damage. It will also reduce the costs associated with additional inhibitory treatment.
Eco-friendly water-based epoxy resins (WEP) coatings are widely applied for surface corrosion protection in marine engineering structures but their anti-corrosion performance needs to be further improved. A novel multifunctional benzotriazole (BTA)-loaded PANI@SiO 2 @h-BN (PSB) composite filler was developed to enhance the anti-corrosion and self-repairing capabilities of WEP coatings. Through sol-gel modification and in-situ polymerization, SiO 2 decoration facilitated the uniform dispersion of two-dimensional hexagonal boron nitride (h-BN) in WEP matrices, while polyaniline (PANI) provided active passivation protection. The synergistic effects of PANI and releasing of BTA inhibitors enable corrosion rates orders of magnitudes lower than pure WEP coating. Electrochemical characterization demonstrated exceptional barrier properties (|Z| at 0.01 Hz > 10 9 Ω cm 2 after 30 days immersion in 3.5 wt% NaCl) and self-repairing functionality through chelate/passivation layer formation. The composite coating exhibited enhanced hydrophobicity, mechanical durability, providing a sustainable solution for marine infrastructure protection.
Due to its lightweight structure, magnesium alloys have been widely used in the automotive and aerospace industries. However, the corrosion resistance of magnesium alloy is a key factor limiting their further application. Rare earth alloying is an economical and effective method to improve the corrosion resistance of magnesium alloys. In this work, Mg–2Y–2Al (wt%) alloy was prepared by conventional casting method. After 168 h of immersion in 3.5 wt% NaCl solution, the corrosion rates determined by hydrogen evolution test and mass loss experiment were 0.57 mm/y and 1.01 mm/y, respectively. The results provide a basic understanding of the synergistic effect of Al and Y on enhancing the corrosion resistance of magnesium alloys. The co-addition of Al and Y is conducive to the formation of a stronger protective film on the alloy surface and effectively inhibits the corrosion of alloys. It provides important insights for the future development of high-performance and corrosion-resistant magnesium alloys.
Metal corrosion is a destructive process that must be managed carefully to prevent unintentional material losses. Most organic and inorganic compounds reported as corrosion inhibitors are highly toxic, causing severe environmental pollution. Recently, expired drugs have been tried as green inhibitors for many metals. The effectiveness of expired drugs as corrosion inhibitors was investigated by techniques such as weight loss, linear polarization, potentiodynamic polarization, and electrochemical impedance spectroscopy methods. The surface morphology of specimen metals was tested before and after the addition of drug inhibitors using scanning electron microscopy, atomic force microscopy, X-ray diffraction, etc., to confirm the inhibition behavior of the drugs. Additional parameters by quantum chemical calculations and molecular dynamics study were computed, and the outcomes agreed with the experimental results. These investigations demonstrated the effectiveness of drugs as corrosion inhibitors and opened up possibilities for managing the disposal of expired drugs. The present paper gives an overview of the usage of expired drugs as efficient inhibitors to control the corrosion of carbon steel and mild steel. The comparison of inhibition performances of different expired drugs and the mechanism of corrosion inhibition have been discussed. The existing challenges faced in using expired drugs as inhibitors were highlighted.
Oil and gas pipelines play an important role in the energy transportation industry, but metal corrosion can affect the safe operation of pipeline equipment. This study uses CiteSpace software to synthesize and analyze corrosion models and keywords from research institutions, countries, and methods related to pipeline corrosion prediction. The investigation into the mechanisms of pipeline metal corrosion, with a specific emphasis on CO 2 and H 2 S corrosion, has revealed that several factors influence the process, including temperature, partial pressure, medium composition and the corrosion product film. In addition, the study provides a comprehensive review of pipeline corrosion prediction methods and models. These include traditional empirical, semi-empirical, and mechanism-based prediction models, as well as advanced machine learning techniques such as random forest, artificial neural network model, support vector machine, and dose-response function. Although there are many ways to improve model performance, no universally accepted methods have been established. Therefore, further in-depth research is needed to improve the accuracy of these models and provide guidance for improving the operational safety of pipelines.
