Self-healing polymer coatings are a type of smart material aimed for advanced corrosion protection of metals. This paper presents the synthesis and characterization of two new UV-cure self-healing ...coatings based on acrylated polycaprolactone polyurethanes. On a macroscopic scale, the cured films all show outstanding mechanical properties, combining relatively high Young’s modulus of up to 270 MPa with a strain at break above 350%. After thermal activation the strained films recover up to 97% of their original length. Optical and electron microscopy reveals the self-healing properties of these coatings on hot dip galvanized steel with scratches and microindentations. The temperature-induced closing of such defects restores the corrosion protection and barrier properties of the coating as shown by electrochemical impedance spectroscopy and scanning vibrating electrode technique. Therefore, such coatings are a complementary option for encapsulation-based autonomous corrosion protection systems.
Since 2010, China's economic growth has stagnated due to an unbalanced regional industrial structure and lack of sufficient qualified technical personnel. A nonlinear autoregressive distributed lag ...(NARDL) model has been used in this study to examine the asymmetric effects of secondary vocational education and training (SVET) and higher vocational education and training (HVET) and their interaction with high-tech industries on economic growth over the period 1980–2020. The findings show that an increase in secondary vocational education and training (SVET) significantly boosts long-term economic growth, while a decrease in secondary vocational education and training (SVET) insignificantly reduces long-term China economic growth. Likewise, the upward change in higher vocational education and training (HVET) promotes and the downward fluctuation in higher vocational education and training (HVET) significantly reduces China's long-term economic growth. The moderating role of secondary vocational education in the impact of high-tech industries on China's economic growth is positive, but not significant. However, higher vocational education plays a significant positive moderating role in high technology industries impact on economic growth. Strategically, the study analysis suggests that economic transition prosperity can be achieved by encouraging higher vocational education and the equal development of high-tech industries in all regions. In addition, this study also proposes to cultivate high-quality talents related to high-tech development and modern industrial innovation and upgrading through higher vocational education, improve productivity, and promote the country's intensive development.
Since 2010, China's economic growth has stagnated due to an unbalanced regional industrial structure and lack of sufficient qualified technical personnel. A nonlinear autoregressive distributed lag ...(NARDL) model has been used in this study to examine the asymmetric effects of secondary vocational education and training (SVET) and higher vocational education and training (HVET) and their interaction with high-tech industries on economic growth over the period 1980-2020. The findings show that an increase in secondary vocational education and training (SVET) significantly boosts long-term economic growth, while a decrease in secondary vocational education and training (SVET) insignificantly reduces long-term China economic growth. Likewise, the upward change in higher vocational education and training (HVET) promotes and the downward fluctuation in higher vocational education and training (HVET) significantly reduces China's long-term economic growth. The moderating role of secondary vocational education in the impact of high-tech industries on China's economic growth is positive, but not significant. However, higher vocational education plays a significant positive moderating role in high technology industries impact on economic growth. Strategically, the study analysis suggests that economic transition prosperity can be achieved by encouraging higher vocational education and the equal development of high-tech industries in all regions. In addition, this study also proposes to cultivate high-quality talents related to high-tech development and modern industrial innovation and upgrading through higher vocational education, improve productivity, and promote the country's intensive development.
•Intermetallic compounds Mg2Ca and MgZn2 were successfully fabricated.•Real-time in situ monitoring of the current density, pH value and Mg2+ concentration of galvanic couples were ...conducted.•Self-forming cathodes on the anode along with anodic reaction were recorded.•Corrosion behavior of intermetallic MgZn2 in Hank’s solution was evaluated.•A mechanism involving galvanic corrosion and corrosion products forming was illustrated.
The purpose of this study is to comparatively investigate on intermetallic compounds Mg2Ca and MgZn2 in galvanic corrosion of magnesium alloy by using real-time in situ monitoring techniques. The results indicated Mg2Ca functioned as an anode with higher anodic current density, higher Mg2+ concentration and higher pH values than the Mg cathode, while MgZn2 worked as a cathode with a cathodic current density, lower Mg2+ concentration and higher pH value than the anodic Mg. The results also suggested a corrosion forming mechanism involving solubility product constant (Ksp) in which Zn-based corrosion products were easier to form than their Mg counterparts.
The co-polymerization of aniline with p-nitroaniline has been synthesized in oxalic acid medium, here ammonium persulfate (APS) acts as an oxidant. TGA analysis was used to study the thermal ...stability of the copolymer, as well as FTIR, UV–Vis spectroscopy, and XRD. The synthetic poly (aniline-co-p-nitroaniline) (PANA) is used as a barrier/redox pigment for PANA coatings. The anti-corrosion study on PANA coatings was performed with a 3% NaCl solution for up to 35 days. The coating resistance of PANA coatings is three orders of magnitude more than that of pure epoxy coatings, according to the results of electrochemical impedance spectroscopy (EIS). The scanning vibrating electrode method (SVET) was used to investigate the self-healing characteristics of this PANA coating.
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•The poly (aniline–co-p-nitroaniline) (PANA) is prepared by a chemical oxidation route.•The PANA doped oxalate ion acts as an inhibitor at the onset of corrosion.•The corrosion protector of PANA was studied by EIS.•The imitated corrosion process of PANA was studied by SVET.•The superior corrosion protection of PANA is better than epoxy coating.
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•GO with different aspect ratios were prepared and the uniform GO/epoxy composite coatings were fabricated.•Anti-corrosion performance of composite coatings containing GO sheets with ...different aspect ratio were investigated.•Anti-corrosion mechanism of different GO/epoxy composite coatings were studied.•The aspect ratio of GO sheets was a significant factor for enhancing corrosion resistance of GO/epoxy coatings.
Graphene oxide (GO) has a wide application prospect in the field of metal protection due to its good dispersion, chemical activity and physical barrier property. Herein, graphene oxide sheets with different aspect ratio were first prepared by simply controlling the procedure of chemical exfoliation and then used to fabricate GO/epoxy composite coatings. The morphology and structural features of as-prepared GO sheets were characterized by Raman spectroscopy, X-ray diffraction and atomic force microscopy. The dispersion and anticorrosive performances of GO with different aspect ratios incorporated in epoxy-based waterborne composite coatings were investigated by Raman spectroscopic mapping, electrochemical measurements and scanning vibrating electrode technique. The results demonstrated that the different types of GO showed homogeneous dispersion in epoxy resin and GO with higher aspect ratio exhibited larger corrosion protection potential. Furthermore, the anti-corrosion mechanisms for composite coatings enhanced via GO with different aspect ratio were tentatively proposed, which indicating that the GO sheets with higher aspect ratio provided a more tortuous permeation path for corroding medium and thus displayed better corrosion resistance.
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•Microstructural studies of 2524-T3 Al alloy welded by FSW were performed.•Corrosion resistance of the base material and nugget zone was assessed by EIS and SVET.•Base material and ...nugget zone possess a cathodic behaviour.•The influence of FSW process on FCG curves in nugget and base material was studied.
The corrosion processes and its influence on the FCG curves of the 2524-T3 alloy joined by FSW was studied in the nugget and BM. To assess the corrosion process, SVET, pH micro-potentiometry and EIS were used. The localised corrosion results showed similar BM and nugget zone electrochemical behaviour, while the TMAZ/HAZ region was electrochemically the weakest zone, susceptible to anodic dissolution. The FSW process and saline environment was found to modify the BM and nugget FCG resistance, being more detrimental for the BM due to the primary IM particles that are not present in the nugget, making it chemically more homogeneous.
•The physico-chemical model of galvanic corrosion AA2024-Ti was developed.•Local corrosion effects and formation of porous corrosion products were considered.•The diffusion layer for O2 was ...introduced, although convection was not considered.•A qualitative agreement was found between the model and experiment.
This study focuses on the development of a physico-chemical model based on mechanistic and kinetics understanding of the corrosion process in galvanic couple Ti6Al4V-AA2024. Proposed model provides deeper insights at macro level for initiation and propagation of localized corrosion of AA2024 in galvanically coupled multi-material assemblies. The model is able to reveal the localized corrosion, related to heterogeneity of AA2024 microstructure, including local pH changes, the deposition of the reaction products, and emphasizes the important role of AA2024 self-corrosion in galvanic assemblies. The validation of the developed model was performed using relevant data collected by advanced in situ localized techniques.
•Copper protection in 3.5 wt.%NaCl by 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol (PyODT).•High inhibitive efficacy of PyODT on Cu corrosion was reached at long exposure.•A uniform and compact inhibitor ...film was formed on copper surface.•Interaction between Cu and PyODT proceeded through thiol and oxadiazole groups.•Machine learning algorithms and Raman data were firstly applied in corrosion study.
An oxadiazole derivative with functional groups favouring its adsorption on copper surface, namely 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol, has been explored as potential inhibitor of copper corrosion in 3.5 wt.% NaCl. Electrochemical evaluation by electrochemical impedance spectroscopy, potentiodynamic polarization and SVET reveals high inhibition efficiencies. Surface microscopy inspection and spectroscopic analysis by Raman, SEM-EDX and XPS highlight the formation of a compact barrier film responsible for long-lasting protection, that is mainly composed of the organic molecules. Machine learning algorithms used in combination with Raman spectroscopy data were applied successfully for the first time in corrosion studies to allow discrimination between corroded and inhibitor-protected metal surfaces. Quantum Chemistry calculations in aqueous solution and Molecular Dynamic studies predict a strong interaction between copper and the thiol group and an extensive coverage of the metal surface, responsible for the excellent protection against corrosion.
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In order to study the effect of defects on the corrosion behavior of MAO coatings, global electrochemical method including potentiodynamic polarization (PDP) and electrochemical impedance ...spectroscopy (EIS) was used to measure the corrosion resistance of MAO coatings. Local electrochemical measurements including local impedance spectroscopy (LEIS) and scanning vibrating electrode technique (SVET) were used to study the local corrosion mechanism. The confocal microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to observe the microstructure and phases of the samples. Results of global electrochemical measurement demonstrate that the scratches cause the reduction of the impedance and the increase of the corrosion current density. LEIS results show the impedance value distribution of the coating with the scratch. With the changes over time, the minimum impedance value of the scratch decreases first and then increases from the third hour. SVET results show the corrosion current density distribution of the scratched coating. The maximum corrosion current density at the scratch increases first and then decreases. The results of local electrochemical measurements show that the corrosion rate at the scratch decreases when the reaction lasted 3 h. Confocal microscopy found that the scratch is expanding with increasing time, and the depth and cross-sectional area of the coating is 5 times deeper and 10 times larger than that of 7075Al with scratch at the first 6 h. The 6-day immersion test proved that the scratch coating still has the protective effect on the substrate. The main corrosion product is Al(OH)3. A physical model reflecting the mechanism of the scratch propagation and the formation of the corrosion product film is proposed.
•Global and local electrochemical corrosion of scratched MAO coating on Al Alloy was studied.•The electrochemical impedance and current distribution of scratches were analyzed by LEIS and SVET.•A phenomenological model for the influence of scratch on the local corrosion of the MAO coated Al alloy was proposed.
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