Evaluation of the active corrosion protection and self-healing properties of a silane sol-gel coating doped with Zn-Al-PO_4~(3+) layered double hydroxide nanoparticles

摘要

The influence of incorporation of layered double hydroxide (LDH) nanoparticles, as a smart corrosion inhibitor, into an eco-friendly silane layer was studied. The silane composite was made of the mixture of tetraethoxysilane (TEOS) and 3-Aminopropyl triethoxysilane (APTES) silanes applied on the mild steel substrate. At first, Zn-Al LDH with nitrate as the charge balancing anion in the interlayer space was synthesized via a co-precipitation route. Then, the Zn-Al-NO_3~- LDH nanoparticles were loaded with phosphate ion through anion-exchange reaction to synthesize Zn-Al-PO_1~(3-) LDH. The nanoparticles were characterized by Fourier transform infrared (FT-1R) spectroscopy and scanning electron microscopy (SEM). Then, the active corrosion protection properties of the LDHs were investigated by an electrochemical noise (EN) technique. In this paper, a multi-resolution wavelet analysis was performed for feature extraction from the electrochemical signals. In this regard, the electrochemical signals are decomposed in predefined number of scales (or crystals) in undecimated wavelet transform (UWT) framework. EN data revealed that the silane coating in the presence of Zn-AI-PO_4~(3-) could provide superior corrosion protection and self-healing properties compared to the sol-gel film which is solely incorporated with Zn-Al-NO_3~-. Further, addition of LDHs namely Zn-Al-NO_3~-and Zn-Al-PO_4~(3-) to the sol-gel film increased its barrier properties due to their planar structure.