Domain size and thermal stability of amine-cured hybrid films as corrosion resistance treatments for aluminum alloy

Amine-cured Ormosil coatings were prepared from tetraethylenepentamine (TEPA), 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethoxysilane (TEOS) by sol–gel method. These Ormosil films were deposited by spin coated on aluminum alloy to improve the corrosion protection. The effect of the concentration of curing agent TEPA on the chain dynamic, domain size, thermal stability and corrosion performance of coated samples was investigated. The rotating frame spin–lattice relaxation times (T1ρH) and scale of the spin-diffusion path length (L) indicated that the configuration of the Ormosil films was highly crosslinked and dense and adhered to the aluminum alloy (AA) substrates. The thermal stability and the apparent activation energy (Ea), evaluated by van Krevelen’s method, of the TEPA-cured GPTMS–TEOS Ormosils decreased with increasing TEPA content. Potentiodynamic and salt-spray analysis revealed that the Ormosil films provided exceptional barrier and corrosion protection in comparison with untreated AA substrates.