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.Keywords:PEO coating;silane polymer;sealing treatment;corrosion resistance
Shuai Zhang,Yinlong Ma,Sixu Zhao,Wenhao Dai,Baochang Liu
A modified cerium seal PEO pretreatment was developed on 2A14 alloy and combined with an epoxy coating (EP) to form a duplex coating system. The PEO coating was effectively sealed by cerium hydroxides and oxides , and also acted as a controlled release vessel for the cerium salt corrosion inhibitor , and significantly improved the adhesive strength of the EP. The results of electrochemical tests and immersion experiments show that the coating system pretreated with the modified cerium seal PEO exhibits excellent long-term corrosion resistance and active protection. This is attributed to the physical barrier of insoluble cerium-based compounds and sensitive pH-responsive deposition.
Micro-arc oxidation (MAO) has gained widespread adoption in aluminum alloy protection due to their remarkable corrosion resistance. Nevertheless, the inherent microporous defects of MAO layer persist in exposing the substrate to corrosive damage during operational conditions. While silane-based sealing techniques have emerged as a promising solution for these defects, their practical implementation still faces critical challenges including insufficient defect-filling capacity and compromised mechanical durability. The present work employs electrochemical-assisted method that selectively generates hydroxyl/hydroxide ions at microporous defect sites within the MAO layer. Such local alkalinization conditions enable the directed assembly of silane hydrolysis products, driving interfacial adhesion-condensation reactions to achieve in situ silane film deposition with spatial selectivity. The optimized sealing system demonstrates a 50 % improvement in long-term corrosion resistance (150 MΩ·cm 2 ) compared to conventional impregnation methods, accompanied by significantly enhanced self-cleaning, wear-resistant property. This provides a solution for the multifunctional anti-corrosion, wear-resistant, self-cleaning of aluminum alloy surfaces.
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