Improvement of the film thickness by modification of the hydroxymethylbenzene SAM with tetraethoxysilane and octanediol for protection of iron from corrosion in 0.5M NaCl

Abstract For enhancing the protective efficiency, P of a film prepared by modification of a p -hydroxymethylbenzene HOC 6 H 4 (HOMB) self-assembled monolayer (SAM) adsorbed on iron by the formation of a covalent bond, an increase in the film thickness, d was attempted. The HOMB SAM was modified with tetraethoxysilane (C 2 H 5 O) 4 Si (TES), 1,8-octanediol HO(CH 2 ) 8 OH (C 8 DO), 1,2-bis(triethoxysilyl)ethane (C 2 H 5 O) 3 Si(CH 2 ) 2 Si(OC 2 H 5 ) 3 (BTESE) and alkyltriethoxysilane C n H 2 n +1 Si(OC 2 H 5 ) 3 (C n TES, n = 8 or 18). The P value of the film was determined by polarization measurement of a covered iron electrode in an aerated 0.5 M NaCl solution after immersion in the solution for 1.5–72 h of the immersion time, t . High values of P , more than 82% were obtained for the films of HOMB SAM modified with TES, C 8 DO and C n TES and with TES, C 8 DO, BTESE and C n TES in the range of t up to 72 h. The highest value was 93.2%, for the film of HOMB SAM modified with TES, C 8 DO, BTESE and C 18 TES, of which d was 4.7 nm. The film of HOMB SAM modified with TES, C 8 DO and C 8 TES was characterized by contact angle measurement, X-ray photoelectron spectroscopy and FTIR reflection spectroscopy.