Corrosion resistance of the anodization/glycidoxypropyltrimethoxysilane composite coating on 6061 aluminum alloy

• Published in: Surface & coatings technology 2020-12, Vol.403, p.126433, Article 126433
• Main Authors: Telmenbayar, Lkhagvaa, Ramu, Adam Gopal, Yang, Daejeong, Song, Minjung, Erdenebat, Tumur-Ochir, Choi, Dongjin
• Format: Article
• Language: English
• Subjects: Adhesion tests; Adhesive strength; Aluminum alloy; Aluminum base alloys; Anodizing; Chemical composition; Corrosion resistance; Corrosion resistant alloys; Dipping; Hot water; Morphology; Pitting (corrosion); Protective coatings; Salt spray tests; Scratch tests; Sealing; Silanization; Siloxanes
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2020.126433

An anodization/γ-glycidoxypropyltrimethoxysilane (GPTMS) composite coating was prepared via anodization, followed by a siloxane sealing treatment with and without pre-sealing to improve the corrosion resistance of the 6061 Al alloy. Hot water sealing (HWS) was used as for pre-sealing, while the spinning and dipping methods for siloxane sealing treatment were compared. The morphology, structure, and chemical composition of the coatings with and without sealing were characterized by FE-SEM, EDS, FTIR, and XRD. It was found that the porous anodic film was completely sealed in the double-sealed samples, including the AHD (anodized/hot water pre-sealed/GPTMS sealed by the dipping process) and AHS (anodized/hot water pre-sealed/GPTMS sealed by the spinning process) coatings. In addition, the corrosion resistances of the coatings were evaluated using a potentiodynamic polarization test and salt spray test. The results indicated that the siloxane-sealed samples had significantly higher corrosion resistance than the hot water-sealed sample. The AHD and AHS coatings exhibited excellent corrosion resistance with absence of pitting corrosion after 336 h salt spray test. Moreover, scratch tests were carried out to measure the adhesion strength of the coatings, and the results revealed that the AHS coating had excellent adhesion strength. The effect of pre-sealing treatment on the anodized sample was also discussed. •Composite coatings prepared via anodization, followed by silanization treatment on 6061 Al alloy.•Pre-sealing treatment significantly influenced the subsequent growth of siloxane layer.•Pore-free surface morphologies obtained by double sealed coatings.•Siloxane sealed coatings exhibited excellent anticorrosion properties.•The spin-assisted silane sealing enhanced the adhesion strength of the anodic coating up to 18.57 N.