Effect of the Coating Deposition Technique on the Protective Properties of Hybrid Sol-Gel on AA2024-T3

The deposition technique effect on the corrosion properties of thin films applied on AA2024-T3 was evaluated. The deposition techniques were spin-coating, dip-coating, brush painting and spray painting. For each technique different parameters were varied in accordance to its nature of deposition. The coating synthesized by the sol-gel method carried out by a copolymerization of 3-Glycydoxypropyltrimethoxysilane (GPTMS) and tetra-n-propoxyzirconium (TPOZ) was deposited on AA2024-T3 substrate. Scanning electron microscopy (SEM) and roughness measurements revealed that the spin-coating method formed a more homogenous film. The time deposition and the surface finishing significantly modified the bond strength between substrate and sol-gel coating. The corrosion properties were assessed by Electrochemical Impedance Spectroscopy (EIS). These results revealed that the spin-coating technique not only provides better corrosion properties of the sol-gel but also a marked improvement of the corrosion resistance on aluminum at larger immersion times in saline media. The combination of ground finishing in conjunction with time deposition modifies significantly the dielectric properties of the sol-gel coating.