Spectroscopic and corrosion resistance characterization of amine and super acid-cured hybrid organic–inorganic thin films on 2024-T3 aluminum alloy

Primary aliphatic amines (diethylenetriamine, triethylenetetramine, tetraethylenepentamine) and super acids (CF 3SO 3H, HPF 6) have been investigated as room temperature curing agents for hybrid organic–inorganic thin films. 1 H- 13 C CP/MAS NMR analysis indicates that the curing mechanisms promoted by amines and super acids are different, producing Ormosils (organically modified silicates) with different structures. Amine-cured Ormosils were found to be highly crosslinked, dense, and adherent to the underlying aluminum alloy (AA) substrate; analogous super acid-cured Ormosils were oligomeric, exhibiting poor adhesion properties to the underlying metal substrate. The choice of the curing agent was found to affect the Ormosil film corrosion resistance characteristics as indicated by results of potentiodynamic polarization curves and accelerated corrosion tests. Amine-cured films provided corrosion protection, with R corr=37–157 kΩ cm 2, the magnitude of which depended on several processing parameters including stir time prior to amine addition and amine chain length. Super acid-cured films provided poor corrosion resistance, R corr=1–2 kΩ cm 2.