Self-healing polymer coatings with cellulose nanofibers served as pathways for the release of a corrosion inhibitor

Polymer coatings containing cellulose nanofibers were applied to carbon steel for corrosion inhibition. The specimens were scratched with a knife-edge, and then polarization resistance was monitored in a sodium chloride solution. The polarization resistance of the scratched specimen containing nanofibers and corrosion inhibitor was higher than that of a polymer coating that contained only a corrosion inhibitor. The optimal mixing ratio of corrosion inhibitor for cellulose nanofibers was 4. Empty holes were confirmed on a cross-section of the polymer coating after the corrosion test, which showed that the nanofibers served as pathways for the release of the corrosion inhibitor.     

Copper(II) 8-hydroxyquinolinate 3D network film with corrosion inhibitor embedded for self-healing corrosion protection

This work presents a self-healing protective coating for copper. The complex coating is composed of copper(II) 8-hydroxyquinolinate (Cu(8HQ)₂) 3D network film storing corrosion inhibitor as base layer and epoxy as top layer covering on the base layer. The results of EIS and polarization curves reveal the self-healing effect of Cu(8HQ)₂ 3D network film with corrosion inhibitor embedded. After being scratched with a knife-edge, the complex coating rapidly releases inhibitor embedded in 3D network structure to suppress the corrosion process. The scratch on the coating is covered with inhibitor adsorption film and the anodic activity is restrained.     

Polybenzoxazine/SiO2 nanocomposite coatings for corrosion protection of mild steel

A series of nanocomposite coatings (PBS) consisting of silane functional polybenzoxazine (PB-TMOS) and SiO₂ nanoparticles were developed for corrosion protection of mild steel. The influence of silica content on corrosion resistance of PBS coatings was investigated by electrochemical measurements. The surface chemistry of nanoparticles and its effect on morphology of the PBS coating was also studied utilizing Fourier Transforms Infrared Spectroscopy, ²⁹Si Nuclear Magnetic Resonance and Scanning Electron Microscopy analyses. The results indicate that the presence of the covalent bond between nanoparticles and PB-TMOS, greatly improves the interfacial interactions at the polymer/filler interfaces resulting in a better corrosion performance.     

Influence of polyaniline and ceria nanoparticle additives on corrosion protection of a UV-cure coating on carbon steel

Influence of a few percents additives of polyaniline doped with phosphoric acid (PAni-PA) and ceria nanoparticle on corrosion protection of a new ultraviolet (UV)-cure polyester acrylate coating have been studied for coil coating on carbon steel by electrochemical measurements during exposure to a NaCl solution. The results demonstrate that the presence of ceria nanoparticles improves the barrier property and stability of the coating. Adding the PAni-PA results in active corrosion protection for carbon steel due to passivation of the steel, and the combination of both additives greatly enhances the protection property over that of the coating matrix alone.     

Direct-to-metal UV-cured hybrid coating for the corrosion protection of aircraft aluminium alloy

Finding eco-efficient and environmentally viable alternatives to chromate coatings represents a fundamental milestone in the aerospace industry. Here, we show a chromate-free approach to protective hybrid coatings on aluminium alloy (AA2024-T3) departing from photoinduced sol–gel and cationic polymerizations. Beginning with a film of n-alkyltrimethoxysilane and diepoxy monomer, we rely on photogenerated superacids to induce the single step formation of two inorganic and organic barrier networks. Such system combines the unique aspects of photopolymerization including fast reactions, temporal control, solvent-free composition and temperature independence. Used without chemical conversion coating or anodizing, some films have passed 2000 h of salt spray testing.     

Direct electrosynthesis of polyaniline–montmorrilonite nanocomposite coatings on aluminum alloy 3004 and their corrosion protection performance

Homogeneous and adherent polyaniline–montmorrilonite (MMT) nanocomposite coatings were electrosynthesized on aluminum (Al) alloy 3004 (AA 3004) by using the galvanostatic polarization method. The synthesized coatings were characterized by UV–Vis absorption spectrometry, Fourier transform infrared spectroscopy, X-ray diffraction patterns and scanning electron microscopy. The corrosion protection effect of the coatings was demonstrated by performing a series of electrochemical experiments of potentiodynamic and impedance measurements on Al in 3.5 wt% aqueous NaCl electrolytes. The corrosion current (i_corr) values decreased from 6.55 μA cm⁻² for uncoated Al to 0.102 μA cm⁻² for nanocomposite-coated Al under optimal conditions.     

A new corrosion inhibitor for copper protection

Methyl 3-((2-mercaptophenyl)imino)butanoate (MMPB) was synthesized as inhibitor compound for copper protection. The molecule was designed with azole, thiol functional groups and carboxylate tail group. The inhibition efficiency was examined in acidic chloride media, by means of various electrochemical and spectroscopy techniques. Electrochemical study results showed that high efficiency of MMPB was mainly related with its capability of complex formation with Cu(I) at the surface. The thiol group also improves the adsorptive interaction with the surface, as the carboxylate groups provide extra intermolecular attraction.     

Multifunctional epoxy coatings combining a mixture of traps and inhibitor loaded nanocontainers for corrosion protection of AA2024-T3

This work aims at investigating the corrosion protection effectiveness of multifunctional epoxy coatings modified with pigments such as ceramic nanocontainers loaded with corrosion inhibitor, chloride and water traps, applied on AA2024-T3. Characterizations on the morphology, composition and structure of the coatings were conducted. The corrosion resistance was studied by electrochemical impedance spectroscopy, localized electrochemical impedance spectroscopy and scanning vibrating electrode technique. The mechanical behaviour of the coatings was examined through nanoindentation and nanoscratching tests. Electrochemical and nanomechanical testing results, evidenced the improvement of the corrosion protective properties and mechanical behaviour of the coatings in the presence of the various pigments.     

The behaviour of praseodymium 4-hydroxycinnamate as an inhibitor for carbon dioxide corrosion and oxygen corrosion of steel in NaCl solutions

Praseodymium 4-hydroxycinnamate (Pr(4OHCin)₃) was investigated as a novel corrosion inhibitor for steel in NaCl solutions, and found to be effective at inhibiting corrosion in both CO₂-containing and naturally-aerated systems. Surface analysis results suggest that the corrosion inhibition ability of Pr(4OHCin)₃ in the naturally-aerated corrosion system could be attributed to the formation of a continuous protective film. For the CO₂-containing system, the corrosion inhibition efficiency of Pr(4OHCin)₃ was predominantly because of formation of protective inhibiting deposits at the active electrochemical corrosion sites, in addition to a thinner surface film deposit.     

Zinc corrosion protection with 1,5-diphosphono-pentane

A set of identical measurement was performed to characterize the corrosion behaviour in Na₂SO₄ solution and surface structure of layers formed in aqueous and ethanol solutions of 1,5-diphosphonic acid on mechanically polished zinc substrates in order to understand the inhibition mechanism. Although, the protective layers formed in ethanol and in aqueous solution show substantial differences, their protection efficiency tends to the same value after about 4 h in corrosion tests. Based on EIS, XPS and GD-OES data, a simple oxide–hydroxide/diphosphonate model of the interface is proposed.     

Blue tetrazolium as a novel corrosion inhibitor for cold rolled steel in hydrochloric acid solution

The inhibition effect of blue tetrazolium (BT) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution at 20 °C was investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) methods. The results show that BT is a very good inhibitor, and the adsorption of BT on CRS surface obeys Langmuir adsorption isotherm. Polarization curves reveal that BT acts as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of BT is also evidenced by SEM images.     

Benzyltrimethylammonium iodide as a corrosion inhibitor for steel in phosphoric acid produced by dihydrate wet method process

The inhibition effect of benzyltrimethylammonium iodide (BTAI) on the corrosion of cold rolled steel (CRS) in phosphoric acid produced by dihydrate wet method process (7.0 M H₃PO₄) solution was investigated for the first time by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) methods. The results show that BTAI is a good inhibitor, and the adsorption of BTAI obeys Langmuir adsorption isotherm. Polarization curves show that BTAI behaves as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of BTAI is also evidenced by SEM images.     

Characterization and corrosion studies of ceria thin film based on fluorinated AZ91D magnesium alloy

The CeO₂ thin film was prepared via sol-gel method on fluorinated AZ91D magnesium alloy surfaces. The surface morphology, composition and the corrosion resistance of the film were investigated in details using scanning electron microscope, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy as well as potentiodynamic polarization tests. It was found that small amount of MgO and MgF₂ were encapsulated in CeO₂ thin film. The electrochemical measurement results demonstrated that the CeO₂ thin film on fluorinated AZ91D magnesium alloy could improve the corrosion resistance approximately by two orders of magnitude compared with that of the bare substrate.     

The adhesion properties and corrosion performance of differently pretreated epoxy coatings on an aluminium alloy

The influence of various blends of hexafluorozirconic-acid (Zr), polyacrylic-acid (PAA) and polyacrylamide (PAM) pretreatment on the performance of an epoxy coated aluminium substrate was investigated and compared to that of a so-called chromate/phosphate conversion coating (CPCC).Adhesive-strength of epoxy coated substrates was evaluated using pull-off and tape tests. Salt spray, humidity chambers and EIS were employed to characterize corrosion performance of coated substrates with different initial surface pretreatments. Among the Zr-based formulations, PAA/Zr and PAA/PAM/Zr showed the best adhesion strength, while the later revealed a good corrosion performance as well. However, CPCC pretreated sample was still superior in these aspects.     

Corrosion protection of magnesium alloy AZ31 sheets by spin coating process with poly(ether imide) [PEI]

In the present study, the potential of poly(ether imide) as corrosion protective coating for magnesium alloys was evaluated using the spin coating technique. The influence of different parameters on the coating properties was evaluated and the corrosion behaviour of the coatings was investigated using electrochemical impedance spectroscopy. The best corrosion protection was obtained preparing the coatings under N₂ atmosphere, using 15 wt.% solution in N′N′-dimethylacetamide (DMAc) which resulted in a coating of approximately 2 μm thickness, with an initial impedance of 10⁹ Ω cm² and of 10⁵ Ω cm² after 240 h of exposure to a 3.5% NaCl solution.     

Low-temperature atomic layer deposition of Al2O3 thin coatings for corrosion protection of steel: Surface and electrochemical analysis

ToF-SIMS, XPS, voltammetry and EIS investigation of the anti-corrosion properties of thin (10, 50 and 100 nm) alumina coatings grown by atomic layer deposition at 160 °C on steel is reported. Surface analysis shows a thickness-independent Al₂O₃ stoichiometry of the coating and trace contamination by the growth precursors. The buried coating/alloy interface has iron oxide formed in ambient air and/or resulting from the growth of spurious traces in the initial stages of deposition. Electrochemical analysis yields an exponential decay of the coating porosity over four orders of magnitude with increasing thickness, achieved by sealing of the more defective first deposited 10 nm.     

Electrochemical techniques for practical evaluation of corrosion inhibitor effectiveness. Performance of cerium nitrate as corrosion inhibitor for AA2024T3 alloy

In this work, a split-cell technique and image-assisted electrochemical noise analysis, which provide minimal perturbation of the freely corroding system and good time resolution, are proposed as a tool for simultaneous investigation of the corrosion inhibition mechanism and assessment of performance. The results obtained are compared with results from traditional electrochemical impedance spectroscopy, disclosing the advantages of these techniques in the evaluation of inhibitor performance. Specific attention is also given to the investigation of corrosion inhibition by cerium nitrate.     

Study of iron benzoate as a novel steel corrosion inhibitor pigment for protective paint films

The aim of this work was to study the lab-synthesized iron benzoate as a novel steel corrosion inhibitor pigment to formulate anticorrosive paint films. The iron benzoate anticorrosive properties were studied by electrochemical and spectroscopic essays employing pigment suspensions. In a second stage, it was evaluated the performance of anticorrosive paint films containing iron benzoate by accelerated (salt spray and humidity chambers) and EIS tests. The protective layer nature grown under the paint films in the salt spray chamber was also assessed.Experimental results shown that ferric benzoate was adequate to formulate anticorrosive paint films with improved anticorrosive assessed.     

On the degradation mechanism of corrosion protective poly(ether imide) coatings on magnesium AZ31 alloy

In previous publications of the authors, good performance of poly(ether imide) as corrosion protective coatings for magnesium AZ31 alloy was reported. It was suggested that during the sample degradation magnesium hydroxide could react with the imide ring forming magnesium polyamate and polyamic acid, but this could not be experimentally confirmed. In the present letter, we confirm the occurrence of this reaction by infrared and X-ray photoelectron spectroscopy and discuss its influence in the corrosion behavior observed in electrochemical impedance spectroscopy tests.     

Studies on enhancement of surface durability for steel surface by camphor oil modified epoxy polyamide coating

Epoxy polyamide coatings are generally used to protect mild steel structures from corrosive atmosphere due to their better adhesion over under prepared surface and effective barrier protection. But the coating has the ability to disintegrate due to UV radiation and high humidity condition. To improve the weatherability and chemical resistance performance of epoxy polyamide, there is a need to modify it with suitable cross linking agent. In this work, it has been found that camphor oil at 5 wt.% as the optimum level to protect the mild steel structures from corrosive electrolyte. Further the impedance study has shown that the resistance exerted by the Camphor oil incorporated coating in 0.5 M NaCl solution after 60 days is 3 × 10⁷ Ω cm² where as the resistance of the coating without this modifier is 3 × 10⁶ Ω cm². The FTIR spectral study indicates that the formation of ether linkages in the dried film and also the other functional groups present in the epoxy polyamide polymer is completely disappeared in the modified coating. Similarly the TG and DTA analysis showed that considerable shift in the degradation temperature has been noticed for the polymer coating with modifier.