Journal
THIN SOLID FILMS
Volume 590, Issue -, Pages 33-39Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.tsf.2015.07.055
Keywords
Aluminum alloy; Organic-inorganic coatings; Scanning Electron Microscopy; Electrochemical Impedance Spectroscopy; Electrophoretic deposition
Categories
Funding
- National Natural Science Foundation of China [21371019]
- Aero Science Foundation of China [2011ZE51057]
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Electrophoretic deposition (EPD) silicon-zirconium organic-inorganic hybrid coatings were applied on LC4 aluminum alloy for corrosion protection. 3-Glycidoxypropyl-trimethoxysilane (GTMS) and Zirconium (IV) n-propoxide (TPOZ) were used as precursors. 3-Aminopropyl-trimethoxysilane (APS) was added to enhance the corrosion protective performance of the coatings. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize morphology, microstructure and component. The results show that the addition of APS leads to the enhanced migration and deposition of positively charged colloidal particles on the surface of metal substrate, which results in the thickness increasing of coatings. However, loading an excessive amount of APS gives a heterogeneous coating surface. The corrosion protective performance of coatings were measured by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results indicate that the addition of APS improves corrosion protective performance of coatings. The optimal addition content of APS is about 15%. The 15% APS coating is uniform and dense, as well as has good corrosion protective performance. The impedance value (1.58 x 10(5) Omega.cm(2), at the lowest frequency) of 15% APS coating is half order of magnitude higher than that of coating without APS, and 15% APS coating always keeps the best corrosion protective performance with prolonged immersion time. This kind of coating is identified with double-structure properties based on the analysis of EIS and potentiodynamic polarization. Furthermore, the equivalent circuit results indicate that the intermediate oxide layer plays a main role in corrosion protection. (C) 2015 Elsevier B.V. All rights reserved.
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