Formation Mechanism and Anticorrosive Properties of Thin Siloxane Films on Metal Surfaces

Abstract

The adsorption of different ethoxysilanes on Al was studied. It was established that during polymolecular adsorption of ethoxysilanes from the vapor phase on aluminum the first monolayer is adsorbed irreversibly with adsorption van der Waals bonds between silane molecules and the aluminum surface. The covalent bonding of silanes with the surface (Al-0-Si bonds) occurs in the presence of adsorbed water on the aluminum surface. The presence of a silane monolayer on Al decreases water adsorption on the surface, and inhibits hydration of the oxide metal film. The formation of a negatively charged siloxane film on the aluminum surface inhibits local metal corrosion, and a positively charged layer activates it in chloride containing media. The formation of the surface siloxane polymer by the modification of metals inhibits the metal dissolution under polymer coatings. It is caused by silane chemisorption and negative charging of the metal surface. The presence of negatively charged groups causes difficulties of an electrostatic character for the migration of aggressive ions to the metal surface. 9-14, 1994.

Electrochemical performance of sol–gel derived phospho-silicate-methacrylate hybrid coatings

“…The E corr of the MEMO and M:E -1:1 samples shift positively as high as 140 mV and 250 mV respectively. The shifting of the E corr values of all the coated samples to the noble direction in comparison to bare MS sample indicates the enhanced corrosion resistance due to the inhibition of anodic reaction [14,15]. Inhibition of anodic reaction is explained as follows: (a) The higher absorption ability of the phosphate groups (compared to Cl À ion) to form stable surface complexes with metallic oxide surfaces and (b) the negative charge of the functional groups (silicate and phosphate) can reject the negative chloride ions, thereby decreasing the chloride ion concentration close to the metallic surface.…”

Polymer Brushes by the “Grafting to” Method

“…[46,47] Thiol and silane approaches have been extended to other metal and oxide surfaces, respectively. [48][49][50][51][52][53][54][55] Furthermore, thiol and silane substances can bear other functionalities and thereby can bring different chemical groups to a surface for further chemical modifications. Numerous examples exist for the utilization of thiol [18,[56][57][58][59][60][61][62][63][64] and silane [14,16,20,21,33,41, reactions for polymer brush preparation via the ''grafting to'' method.…”

Characterization and corrosion performance of poly(pyrrole-siloxane) films on commercial Al alloys

“…Several approaches have been investigated to improve ECPs processability, such as derivatization of monomer molecules and use of surfactantlike doping ions [4,5], as well as adhesion by pre-treating Al substrate either mechanically or performing anodic galvanostatic activation before electropolymerization [6,7]. Parallel to ECPs, silane-based treatments, usually performed by dipping the metal in dilute alcohol or water-based solutions for a short period, have also been intensively studied [8][9][10][11][12]. Among these compounds, organofunctional silanes are most suitable for corrosion protection of various metals and alloys since they provide effective coupling with both metal substrate and organic topcoat [13].…”