Nanoclay-based self-healing, corrosion protection coatings on aluminum, A356.0 and AZ91 substrates

Abstract

Investigations were carried out to explore the feasibility of using Ce3+/Zr4+ encapsulated in environmental friendly nanoclay containers for prolonged corrosion protection of pure aluminum, aluminum alloy A356.0 and Mg alloy AZ91. Dimensions of clay nanotubes were studied using SEM and TEM analysis. They were subjected to pore volume and surface area analysis to confirm the loading of inhibitor into their lumen. The smart nanocontainers loaded with active cationic inhibitor were dispersed in an organic–inorganic hybrid sol–gel matrix synthesized from the hydrolysis and condensation of glycidoxypropyltrimethoxysilane and tetraethoxysilane. The loading of nanocontainers in the matrix sol was optimized. Coatings were generated on pure Al, A356.0, AZ91 substrates using a dip-coating technique and cured at 130°C for 1 h in air. The coated substrates were characterized for their corrosion resistance using potentiodynamic polarization and electrochemical impedance spectroscopic analysis by exposing them to 3.5 wt% NaCl solution for time intervals varying from 1 to 120 h. Micro-Raman spectroscopic studies were carried out to analyze the chemical composition of phases in the scribed area after exposure to corrosive medium. A few coated aluminum substrates were subjected to scanning vibrating electrode technique experiments to study the self-healing mechanism.