Protection of iron against corrosion by coverage with ultrathin two-dimensional polymer films of a hydroxymethylbenzene self-assembled monolayer anchored by the formation of a covalent bond

Abstract

Ultrathin films of two-dimensional polymers were prepared on an iron electrode by modification of a p-hydroxymethylbenzene p-HOCH 2C 6H 4 (HOMB) self-assembled monolayer (SAM) with 1,2-bis(triethoxysilyl)ethane (C 2H 5O) 3Si(CH 2) 2Si(OC 2H 5) 3 (BTESE) and alkyltriethoxysilanes C n H 2 n+1 Si(OC 2H 5) 3 (C n TES, n = 8 and 18). The electrode was derivatized by cathodic reduction of p-hydroxymethylbenzenediazonium tetrafluoroborate HOCH 2C 6H 4N 2BF 4 in an electrolytic acetonitrile solution below 10 °C for 1 h to form the SAM via a covalent bond between carbon and iron atoms. The protective ability of the polymer film against iron corrosion was determined by polarization measurement of the coated electrode in an oxygenated 0.5 M NaCl solution. The protective efficiencies of the polymer films prepared by modification with BTESE plus C 8TES and C 18TES were 63.9% and 68.5% after immersion in 0.5 M NaCl for 1.5 h, respectively. These values were higher than those of the one-dimensional polymer films prepared with the respective C n TES. The film of the HOMB SAM modified with BTESE plus C 8TES was characterized by contact angle measurement using a drop of water and X-ray photoelectron and FTIR reflection spectroscopies. The films of the HOMB SAM modified with BTESE plus C 8TES and C 18TES were persistent during immersion of the coated electrodes in 0.5 M NaCl for many hours by far as compared with the alkanethiol SAM anchored on iron by the formation of a coordinate bond.