Influence of Sealing Treatment on the Corrosion Resistance of PEO Coated Al-Zn-Mg-Cu Alloy in Various Environments

Abstract

In the present work, a coating was prepared on an Al alloy substrate by plasma electrolytic oxidation (PEO). To seal the micro defects in the oxide scale, a siloxane layer was prepared on the PEO coating by sol gel method. The polymer sealant was synthesized from Tetraethoxy silane (TEOS) and methacryloxy propyl trimethoxyl silane (MPTES). The chemical structure of the polymer was studied by Fourier transform infrared spectroscopy (FTIR). The morphologies and microstructure of the PEO coating and siloxane coating were investigated by scanning electron microscopy (SEM). The results showed that siloxane formed a continuous layer on the surface and effectively sealed the micro defects. The corrosion behavior of the coatings in three different corrosion solutions (NaCl, HCl, and NaOH) was examined by electrochemical impedance spectroscopy and potentiodynamic polarization. The corrosion resistance of the sealed coatings was superior to that of the PEO coating because it prevented the penetration of corrosive solutions. The corrosion resistance of the sealed coatings was found to decrease with increasing electrolyte concentration. The work demonstrated that siloxane sealing may greatly enhance the corrosion resistance of Al-based PEO coating in acidic, neutral, and alkaline environments.

A Comprehensive Review on Surface Modifications of Biodegradable Magnesium-Based Implant Alloy: Polymer Coatings Opportunities and Challenges

“…As a result, the future focus may be on enhancing the barrier effect and binding force for a full-life corrosion-resistant service. In this regard, composite coating may be a viable option for increasing the adhesion force of organic biopolymer coating [117][118][119][120][121][122][123][124][125][126][127][128][129][130][131][132][133][134]. Furthermore, the formation of composite coatings not only improves corrosion resistance but also endows the Mg alloys with potential bioactivity and biocompatibility in long-term tests.…”

Enhanced corrosion‐resistant performance of the PEO coatings on AA7075 alloy by a sol–gel‐derived silica layer

“…Sol–gel‐derived siloxane sealing layers were found to greatly enhance the corrosion resistance of PEO‐coated Al–Zn–Mg–Cu alloy in acidic, neutral, and alkaline environments. However, the stability of those layers over time in corrosive media was provided 31 . The better corrosion protection performance was observed by Sopchenski et al 32 .…”

Influence of Complex SiF62− Ions on the PEO Coatings Formed on Mg–Al6–Zn1 Alloy for Enhanced Wear and Corrosion Protection

“…Tafel curves were obtained from 4.0 V below the open circuit potential (OCP) to 2 V above the OCP at a scan rate of 1 mV/s. The exposed surface area of the coated specimens to the corrosion solution was~0.75 cm 2 . Corrosion potential and corrosion current density were obtained by curve fitting process of the obtained tafel curves using IVman software provided by the Wonatech Inc. (Seoul, Korea).…”

“…Using PEO process, hard ceramic coatings can be formed on various kinds of light metal alloys using appropriate solutions and additives such as alkaline silicates, phosphates, etc. Though the PEO coatings have comparable mechanical properties, due to porosity and defect issues, however, the coatings need further improvement in regards to corrosion protection, for long-term applications [1][2][3][4][5][6][7].…”