Self-assembly of (3-mercaptopropyl)trimethoxysilane on polycrystalline zinc substrates towards corrosion protection

The ability of thiol groups (X=–SH) to graft on pure zinc surfaces through self assembled monolayers (SAMs) formed by chemisorption of (3-mercaptopropyl)trimethoxysilane, (MeO)3Si–(CH2)3–SH, was investigate and compared to the grafting of n-dodecanethiol, CH3–(CH2)11–SH,—alkanethiol of different chain length (n=11 instead of 3) terminated with a non-reactive functional group (Y=–CH3 instead of—Si(OMe)3). Monolayers are obtained by immersion of mechanically polished zinc substrates in ethanolic solutions, nevertheless this solvent is not the finest choice. The effects of the alkanethiols concentration (10−1, 10−2 and 10−3 M) and of the surface immersion times (t=30 min, 1, 5, 24 h) upon the monolayers’ formation have been evidenced by X-ray photoelectron spectroscopy (XPS). This study highlighted an interesting competition effect between the two reactive tails of the (3-mercaptopropyl)trimethoxysilane molecule.