Crosslinking control of hydrophobic benzoxazine-based hybrid sol-gel coating for corrosion protection on aluminum alloys

Benzoxazine (Bz)-based hybrid sol-gel coating (TEOS-PBz) was prepared by compositing benzoxazine functional silane and Tetraethoxysilane (TEOS) and its distinct crosslinking structures were controlled by a designed curing procedure. The coatings' structures were analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectrums and differential scanning calorimetry. It is evident that a prolonged curing procedure could promote curing of Bz functionality completely with high crosslinking degree in the coating, which is a key factor to the coatings' corrosion resistance. The hydrophobicity of the coating is also taken into account as this is also one of the factors affecting the corrosion protection performance. According to the result of electrochemical impedance spectroscopy, the TEOS-PBz with the maximum static water contact angle of 105.6 +/- 0.4. showed the highest impedance with the value of Rct above 105 O after being immersed in 3.5 wt% NaCl aqueous solution for one week, more than one order of magnitude higher than traditional TetraethoxysilaneGlycidoxypropyltriethoxysilane (TEOS-GPTES) hybrid sol-gel coating. It is possible to conclude that complete curing crosslinking structure with the conversion of Bz structure >94 % and high hydrophobicity contributed by less intermolecular hydrogen bonding ratio in the coating presented better corrosion protection performance.

Automated summary

The study found that a complete curing crosslinking structure with high crosslinking degree contributes to better corrosion protection performance in the coating. Additionally, the hydrophobicity of the coating is also an important factor affecting corrosion protection performance.