This study evaluated the corrosion behavior and ion release of assembled orthodontic appliances incorporating different archwire alloys in artificial saliva with and without fluoride, focusing on localized degradation and the susceptibility of welded joints. Two additional appliances with titanium brackets and stainless steel archwires were evaluated exclusively in fluoridated saliva as an exploratory, descriptive assessment. Thirty-two fixed orthodontic appliances (30 stainless steel and 2 titanium brackets) were tested under controlled electrochemical conditions. Half of the stainless steel samples were exposed to fluoridated saliva (0.2% NaF), while the other half served as controls. Titanium brackets were tested exclusively in fluoridated saliva. Electrochemical characterization was performed using polarization measurements and chronoamperometry at 37 °C to assess the electrochemical behavior of the assembled appliances. Surface degradation was analyzed via optical and scanning electron microscopy (SEM), and ion release was quantified using atomic absorption spectroscopy. In fluoride-containing artificial saliva, the highest measured nickel concentration was associated with appliances incorporating thermoactivated NiTi archwires (147 ng/g), whereas the highest chromium concentration was associated with appliances incorporating β-Ti archwires (122 ng/g). These concentrations represent release from the complete assemblies rather than from the archwires alone. Stainless steel brackets showed localized corrosion in spot-welded areas, with steady-state potential shifting from +60 mV (ECS) in non-fluoridated saliva to approximately 0 mV (ECS) in fluoridated conditions. The two appliances with titanium brackets exhibited different current–time responses, which were interpreted descriptively and did not establish the comparative corrosion resistance of the bracket material. Fluoride accelerates the localized degradation of nickel–titanium archwires and spot-welded stainless steel components, though non-fluoridated saliva demonstrated greater overall electrochemical aggressiveness due to chloride activity. The exploratory findings for appliances with titanium brackets require confirmation using larger samples and matched control groups.
Pipeline transportation systems (PTS) move oil and gas reliably and economically, but internal and external corrosion threaten their mechanical integrity. This systematic review examines how microscopic analysis, image processing, and artificial intelligence (AI) have been used to identify, monitor, and predict corrosion in oil and gas PTS. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement, we searched Scopus and Web of Science for English- and Spanish-language records from 1987 to 2025, with the last search in August 2026. Of 1085 records, we removed 270 duplicates and excluded 536 that failed three quality-assessment questions. This left 279 studies from 1987 to 2024 for narrative synthesis. We did not apply a formal risk-of-bias tool. AI-based modeling was the largest cluster with 152 studies, followed by corrosion processes (57), microscopy (40), and image processing (30). A total of 141 studies provided open data. Monte Carlo simulation and Bayesian networks were the most commonly applied AI methods to real pipelines, appearing in 82% and 72% of studies, respectively. A sixteen-criterion matrix applied to twenty representative works showed that they met 3 to 12 criteria, with a mean of 5.85. Only two studies covered all four clusters. This result was robust to cluster-weighted scoring (Spearman ρ = 0.94). Integrated, AI-supported corrosion assessment remains uncommon. Limitations include using only two databases, consensus-based screening, and no meta-analysis. The review was not registered and received no external funding.
The effects of stacking configuration on the environmental durability of carbon fiber-reinforced polymer (CFRP) laminates were investigated under hygrothermal and salt spray aging. Unidirectional [0]n and cross-ply [0/90]n laminates were aged for up to 42 d, and their moisture absorption, chemical structure, dynamic mechanical behavior, flexural properties, and fracture characteristics were evaluated. Hygrothermal exposure produced higher moisture uptake and diffusion rates than salt spray, while the Langmuir model described the absorption behavior more accurately than the Fick model. After 42 d, the glass transition temperatures of the [0]n and [0/90]n laminates decreased by 23.8% and 23.7% under hygrothermal aging compared with 9.0% and 6.9% under salt spray. The corresponding flexural-strength losses were 16.1% and 18.6% versus 9.6% and 10.7%. Although the [0/90]n laminate exhibited slightly lower moisture uptake, it suffered greater strength degradation because transverse cracking in the 90° plies promoted interfacial debonding and delamination. These results show that the environment governs degradation intensity, whereas stacking configuration controls damage propagation and flexural failure.
This study investigated the effects of Nb additions on the microstructure, hardness, and high-temperature oxidation behaviour of mechanically alloyed and spark-plasma-sintered Ti–48Al–2Cr–xNb alloys containing 1–5 at.% Nb. The aim was to clarify the role of Nb in phase evolution, strengthening, and oxidation protection, and to identify factors that limit its effectiveness. Following mechanical alloying and consolidation at 950 °C, the alloys exhibited predominantly globular γ-TiAl/α2-Ti3Al microstructures with localized Nb enrichment. Relative densities remained below 92%, indicating that residual porosity was a significant processing-related factor. The alloy containing 5 at.% Nb exhibited the highest hardness, consistent with Nb-induced solid-solution strengthening and changes in phase constitution. Isothermal oxidation was assessed by measuring weight gain per unit area after exposure at 700 °C for 400 h and at 900 °C for 200 h. At 900 °C, the alloys formed stratified scales consisting primarily of an outer TiO2-rich layer and an underlying Al2O3-rich region. NbO2 was detected in selected samples; however, no continuous, protective Nb2O5-rich scale formed. Preferential TiO2 growth, together with cracking, exfoliation, and spallation, hindered the formation of a fully protective alumina barrier. At 700 °C, exposure for 400 h produced a substantially thinner, non-adherent oxide scale, consistent with the slower oxidation kinetics at lower temperatures. Consequently, increasing the Nb content did not result in a monotonic improvement in oxidation resistance. Overall, Nb enhanced hardness and influenced phase stability but did not, by itself, overcome the oxidation limitations of TiAl. Its effectiveness depends on densification, Al activity, microstructural homogeneity, and scale adhesion.
2-mercaptobenzimidazole (2-MBI) and propargyl-functionalized MBI (propargyl-MBI) as corrosion inhibitors for API 5L X70 steel in CO2-saturated NaCl solution was evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), gravimetric weight loss, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), and atomic force microscopy (AFM). Electrochemical tests showed that both inhibitors reduced corrosion, with propargyl-MBI exhibiting the best inhibition. propargyl-MBI achieving efficiencies of 96.1% by EIS and 97.4% by polarization at 10 ppm. After 96 h, corrosion rates decreased from 2.23 mm·year−1 (blank) to 0.40 and 0.14 mm·year−1 for 2-MBI and propargyl-MBI, respectively. SEM/EDS and AFM confirmed improved surface protection, with roughness decreasing from 142 nm (blank) to 76.8 nm (2-MBI) and 51.1 nm (propargyl-MBI). Adsorption followed the Langmuir model (R2 = 0.99), with ΔG°ads values of −25.1 and −34.25 kJ·mol−1 for 2-MBI and propargyl-MBI, respectively, indicating stronger adsorption after functionalization. Dispersion-corrected density functional theory calculations were used to elucidate the adsorption modes as well as the main interactions between the 2-MBI, in thiol and thione tautomers, and propargyl-MBI. The binding energy as well as the charge transfer were increased in the case of propargyl-MBI.
