Synthesis of stabilized dispersion covalently-jointed SiO2@polyaniline with core-shell structure and anticorrosion performance of its hydrophobic coating for Mg-Li alloy.

Highlights • Covalently-jointed core-shell structure SiO 2 @PANI sol was synthesized by using GPTMS. • SiO 2 @PANI/VTMS sol was prepared by in situ embedding SiO 2 @PANI particles with VTMS. • The sol could form hydrophobic coatings on the surface of Mg-Li alloy directly. • The coatings have better corrosion resistance performance for the active Mg-Li alloy. • Protection is due to the synergistic effect of hydrophobicity, barrier and passivation. Abstract A new method was developed in this paper to obtain self-film-forming polyaniline (PANI) grafting SiO 2 (SiO 2 @PANI) sol which could form hydrophobic coatings on the surface of magnesium-lithium (Mg-Li) alloy directly for the purpose of anticorrosion. Firstly, covalently-jointed SiO 2 @PANI sol with core-shell structure was synthesized with (3-glycidoxypropyl)-trimethoxylsilane (GPTMS) modified SiO 2 as core and PANI as shell, and then SiO 2 @PANI/VTMS sol was prepared after embedded SiO 2 @PANI with vinyl trimethoxysilane (VTMS). The structure and morphology of SiO 2 @PANI particle were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The hydrophobic and anticorrosion properties of SiO 2 @PANI/VTMS coating on Mg-Li alloy were evaluated by contact angle, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves. The results showed that aniline is polymerizing on the surface of SiO 2 preferentially through the reaction between the epoxide group in GPTMS and amino group in aniline. The obtained SiO 2 @PANI sol dispersed stably in ethanol and supplied well microroughness to coatings, and subsequently enhanced hydrophobic properties of SiO 2 @PANI/VTMS coatings along with low surface energy supplied by VTMS. The hydrophobic angle of SiO 2 @PANI/VTMS coatings is high up to 133.8°. Consequently, the coatings have better corrosion resistance performance for the active Mg-Li alloy. Its impedance value is 5 × 104 Ω·cm2, and corrosion current density is merely 6.7 × 10−7 A·cm−2. [ABSTRACT FROM AUTHOR]