Corrosion protection of carbon steel by an epoxy resin containing organically modified clay

This study focusses on the use of montmorillonite clay (MMT) treated with an organic compound (aminotrimethylphosphonic acid (ATMP)) and dispersed in an epoxy resin to improve corrosion protection of carbon steel. X-ray diffraction was performed to verify that the individual silicate layers were separated and dispersed in the epoxy resin. Corrosion resistance of the coated steel was evaluated by electrochemical impedance spectroscopy (EIS) and local electrochemical impedance spectroscopy (LEIS). Three systems were tested: the epoxy clear-coat, the epoxy resin containing 2 wt.% clay and the epoxy resin containing 2 wt.% clay modified byATMP (ATMP-modified clay). From conventional EIS, it was shown that the incorporation of clay or ATMP-modified clay in the epoxy matrix significantly improved the barrier properties of the coating. The corrosion resistance of the carbon steel coated by the epoxy resin containing ATMP-modified clay was higher than that obtained for the system containing non-treated clay. Local electrochemical measurements performed on scratched samples revealed the inhibitive role of ATMP at the carbon steel/coating interface

Combination of epoxy coating with cerium-modified clays doped hybrid sol-gel film for active corrosion protection of aluminium alloys

peer reviewedAluminum alloy 2024 (AA2024) is widely used as an important material for aerospace industry. Therefore, with high copper content, AA2024 is susceptible to corrosion, especially pitting or intergranular corrosion. Generally, the pre-treatments exploiting the Cr (VI) compounds have been considered as the most effective conversion layers for protection against corrosion of this alloy due to the strong oxidation properties of Cr (VI). Unfortunately, as they cause problems on human health and the environment, new pre-treatments for corrosion protection have been actively developed in the last decade. This work presents a new approach to develop protective multilayer system of aluminum alloys AA2024 based on the inhibitor efficiency of cerium ions which are considered as a promising alternative to replace chromate compounds. Cerium ions were inserted into nanoclays platelets by cationic-exchange reactions (CeMMT). XRD analysis proved the presence of cerium ions intercalated into clays structure. EIS measurements and polarization curves highlighted a high corrosion inhibition effect of cerium-modified nanoclays. This effeciency can be related to the release of 60 % of cerium ions from CeMMT structure in sodium chloride solution as determined by UV-VIS measurements. EIS measurements revealed that hybrid sol-gel film doped with CeMMT improved barrier properties and anticorrosion protection of aluminum 2024 substrate. Scanning Vibrating Electrode Technique and salt spray test made on scratched sol-gel samples indicated a self-healing effect of cerium ions which provide an active corrosion protection to aluminum substrate. A second layer based on solvent-free epoxy coating was then applied onto hybrid sol-gel film. When combining cerium-nanocontainers doped sol-gel film with epoxy coating, EIS measurements showed a high potential anticorrosion property of this multilayer system to protect aluminum 2024. Results of this research indicated that epoxy coating combining sol-gel film incorporating cerium-nanocontainers can give an active corrosion protection to AA2024. Keyword: Sol-gel, AA2024, corrosion, montmorillonite, cerium salts, EIS, epoxy Acknowledgments: Authors would like to thank ARES/CCD (Belgium) for financial support. Reference: [1] R.L. Twite, G.P. Bierwagen, Progress in Organic Coatings 33 (1998) 91-100. [2] C. Motte, M. Poelman, A. Roobroeck, F. Deflorian, M.-G. Olivier, Progress in Organic Coatings 74 (2012) 326-333. [3] E.A. Matter, S. Kozhukharov, M. Machkova, V. Kozhukharov, Corrosion Science 62 (2012) 22-33 [4] R. Naderi, M. Fedel, F. Deflorian, M.Poelman, M.-G. Olivier, Surface and Coatings Technology 224 (2013) 93-100. [5] M.-E. Druart. I. Recloux, T.T. Thai, S.Ershov, R. Snyders,M.-G. Olivier, Surface and Coatings Technology 304 (2016) 40-50. [6] T.T. Thai, M.-E. Druart, Y. Paint, A.T. Trinh, M.-G. Olivier, Progress in Organic Coatings 121 (2018) 53-63. [7] A.T. Trinh, T.T. Thai, K.O Vu, T.X.H To, A.S. Nguyen, N. Caussé, N. Pébère, Surfaces and Interfaces 14 (2019) 26-33. [8] K.A. Yasakau, M.L. Zheludkevich, M.G.S. Ferreira, Surface Science and Electrochemistry, Reference Module in Chemistry, Molecular Science and Chemical Engineering (2018) 115-12

Hybrid sol-gel coatings doped with cerium -nanocontainers for active protection of aluminium alloys

peer reviewedAbstract Aluminum alloy 2024 (AA2024) is widely used as an important material for aerospace industry. Therefore, with high copper content, AA2024 is susceptible to corrosion, especially pitting or intergranular corrosion. Generally, the pre-treatments exploiting the Cr (VI) compounds have been considered as the most effective conversion layers for protection against corrosion of this alloy due to the strong oxidation properties of Cr (VI). Unfortunately, as they cause problems on human health and the environment, new pre-treatments for corrosion protection have been actively developed in the last decade. This work presents a new approach to develop protective pre-treatment for AA2024 based on the inhibitor efficiency of cerium ions which are considered as a promising alternative to replace chromate compounds. In this study, the inhibition properties of cerium salts for improving the anti-corrosion performance of AA2024 have been characterized by polarization curves and EIS measurements. Cerium ions were inserted into nanoclays platelets by cationic-exchange reactions (CeMMT). XRD analysis proved the presence of cerium ions intercalated into clay structure. EIS measurements and polarization curves highlighted a high corrosion inhibition effect of cerium-modified nanoclays. This effectiveness can be related to the release of 60% of cerium ions from CeMMT structure in sodium chloride as determined by UV-VIS measurements. Scanning Vibrating Electrode Technique and salt spray test made on scratched sol-gel samples indicated a self-healing effect of cerium ions which provide an active corrosion protection to aluminum substrate. EIS measurements revealed that hybrid sol-gel films doped with CeMMT improve barrier properties and anticorrosion protection of aluminum 2024 substrate. Results of this research indicated that sol-gel films incorporating cerium-nanocontainers can give an active corrosion protection to AA2024. Keywords. Sol-gel, AA2024, corrosion, montmorillonite, cerium salts, EIS

Hybrid sol-gel coatings doped with cerium nanocontainers for active corrosion protection of AA2024

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Layered double hydroxides as containers of inhibitors in organic coatings for corrosion protection of carbon steel

The present work focuses on the use of layered double hydroxides (LDH) as containers for corrosion inhibitors in an epoxy coating. 2-Benzothiazolylthio-succinic acid (BTSA), used as corrosion inhibitor, was intercalated by co-precipitation in magnesium-aluminum layered double hydroxides. The obtained LDH-BTSA was characterized by infrared spectroscopy, X-ray diffraction and scanning electron microscopy. BTSA release from LDH-BTSA in NaCl solutions was investigated by UV-vis spectroscopy. The inhibitive action of LDH-BTSA on carbon steel corrosion was characterized by electrochemical methods and the protective properties of an epoxy coating containing LDH-BTSA were evaluated by electrochemical impedance spectroscopy. It was shown that the BTSA was intercalated in the layered double hydroxide and its loading was about 33%. The BTSA release was dependent on the NaCl concentration in the electrolyte. The polarization curves obtained on the carbon steel sample showed that the LDH-BTSA is an anodic inhibitor. Its efficiency was about 90% at a concentration of 3 g/l. The impedance results showed that the incorporation of LDH-BTSA (3%) in the epoxy matrix improved the corrosion protection of the carbon steel

Effect of cast iron microstructure on adherence of an epoxy protection

To study the influence of the microstructure of cast iron on the adhesion of an epoxy coating, ferritic, pearlitic and austempered samples were prepared in as-received, polished and oxidised states. A pull-off test (dry adhesion) was performed before immersing in water while the crosscut test was made after 24 days of exposition in distilled water (wet adhesion). X-rays were combined with optical microscopy (LOM) and scanning electron microscopy (SEM) for surface analysis. The adhesion of the epoxy coating on the cast iron surface firstly depends on the roughness of the surface; polished samples showed high adherence by comparison with asreceived samples. On the oxidised samples, the surface oxide significantly improves the adhesion of the coating in both dry and wet states for all three sample microstructure. The presence of carbide in the structure was observed to decrease adherenc

Incorporation of an indole-3 butyric acid modified clay in epoxy resin for corrosion protection of carbon steel

In the present work, indole-3 butyric acid (IBA) was inserted between montmorillonite clay platelets by cation exchange. The clay treated with the organic compound (IBA-modified clay) was then dispersed in an epoxy resin at a low concentration (2 wt.%). IBA was chosen to act both as an inhibitor and an adherence promoter. The effect of the IBA-modified clay on the microstructure and on the protective properties of the epoxy coating deposited on carbon steel was evaluated by a thermostimulated-current (TSC) method and by electrochemical impedance spectroscopy (EIS). The TSC measurements showed the specific action of IBA-modified clay which decreased the molecular mobility of the polymer chain by comparison with the pure epoxy. Impedance measurements corroborated the role of the modified clay on the barrier properties of the coating which remained high as a function of exposure time in a 0.5 M NaCl solution. The corrosion resistance of the carbon steel coated with the epoxy resin containing IBA-modified clay was significantly higher than that obtained with the clear coat. Polarization curves plotted in the presence of an artificial defect demonstrated the inhibitive role of IBA at the carbon steel/coating interface. The good adherence of the coating was seen during salt spray test

Effect of cerium salts in the cut edge of zinc-based sacrificial coatings: influence of Al and Mg alloying elements on galvanic corrosion

peer reviewedZinc sacrificial coatings alloyed with Al and Mg for sacrificial protection of steel have been developed during the last decades and improved significantly the performance of steel against corrosion compared to pure zinc coating [1]. Despite the significant reinforcement achieved by this sacrificial coating, the cut edges or the appearance of scratches reaching the steel are the major problems due to the formation of galvanic coupling between steel and zinc-based coating. Therefore, it required supplementary active protection for galvanic coupled metallic materials. In previous work [2], cerium chloride has been reported as a promising corrosion inhibitor on the top surface of electro-galvanized steel. Thus, this study aims at investigating the protective properties of cerium salts for the cut edge of zinc-based sacrificial layers. Four types of the sacrificial coating were employed in this study: pure zinc coating on steel (fabricated by electrodeposition), Hot Dip Galvanized steel (HDG), ZA (9 wt. % Al), and ZAM (7 wt. % Al and 4 wt. % Mg). A galvanic corrosion prediction was established through the potentiodynamic polarization curves performed on the top surface of sacrificial coatings and steel in 0.1 M NaCl + 5.10-3 M cerium salts. Then, a local electrochemical technique (Scanning Vibrating Electrode Technique) was conducted on the cross-section of Zn-based coated steel in 0.015 M NaCl + 5.10-3 M inhibitor. In addition, cross-section characterizations of all substrates after 24 h of immersion in the electrolyte solution without and with inhibitor were analyzed by Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy.4617 - ARES PRD 2020 - Vietnam - Renforcement de l'expertise du centre de compétences en protection contre la corrosion et en éléctrochimie - Fédération Wallonie Bruxelles9. Industry, innovation and infrastructur

HIGH PROTECTION PERFORMANCE OF COATING SYSTEMS BASED ON ZINC RICH PRIMER AND FLUOROPOLYMER COATING

Coating systems based on zinc rich primer and fluoropolymer top coat were exposed for 8 years at different atmospheric stations in Vietnam: Hanoi, Ha Long and Nha Trang. For comparison the coating system with zinc rich primer and polyurethane topcoat was also tested. The degradations of coating systems were evaluated by gloss measurement and electrochemical impedance spectroscopy. The obtained results show that coating systems with zinc rich primer and top coatings based on fluoropolymer  and polyurethane topcoats show very high weather resistance and corrosion protection performance, but the systems with fluoropolymer are better than coating system with polyurethane topcoat

8-hydroxyquinoline-modified clay incorporated in an epoxy coating for the corrosion protection of carbon steel

In the present work, a well-known corrosion inhibitor (8-hydroxyquinoline (8HQ)) was inserted within the montmorillonite platelets (8HQ-MMT) and the modified clay was incorporated (3 wt.%) into a solvent-free epoxy coating which was afterwards deposited on carbon steel substrates. First, the inhibitive action of 8HQ was investigated by electrochemical methods carried out on a bare carbon steel rotating disk electrode in a 0.1 M NaCl solution. Then, electrochemical impedance measurements were performed to assess the effect of the 8HQ-MMT in the epoxy coating for the corrosion protection. The results were compared with a reference sample constituted by the epoxy coating containing an ammonium quaternary salt-modified clay. It was shown that the two coatings presented good barrier properties. Dry and wet adherence measurements revealed an improvement of the adherence when the 8HQ-MMT was incorporated into the coating by comparison with the reference sample. It was concluded that the 8HQ mainly had an effect at the metal/coating interface but its concentration was too low to afford significant corrosion protection of the carbon steel