Influence of Gamma Irradiation on a Fatty Acid Self-Assembling Coating of Copper

Abstract

Self-assembled molecules (SAMs) form layers on copper that have an advantage compared to traditional corrosion inhibitors because of the significant decrease of chemical application. The protective properties of such films can be improved by different procedures of application of the SAM layer. In this work, a SAM layer of elaidic acid, a monounsaturated long-chain fatty acid with trans geometrical configuration, was applied on copper surface. Gamma irradiation was used to improve the protective properties of the SAM layer toward corrosion in 3% NaCl. Influence of gamma irradiation on such layer's properties was studied by different electrochemical techniques (polarization measurements, EIS), contact angle measurements and FTIR analysis. The results have shown that gamma irradiation at doses 0.5-5 kGy improves the protective properties of the SAM. The surface film became thinner due to stronger adsorption and resulted in better ordering of molecules on the surface of the oxide film although the polymerization involving the participation of oxygen molecules has been initiated by irradiation.

Green Nanocoatings Prepared by Crosslinking Self‐Assembled Fatty Acids on Metals

“…[ 17 ] It has been shown that in the presence of oxygen, even low doses of radiation up to 10 kGy enhance the protective properties of SAMs by increasing the adsorption of FA molecules on the surface. [ 6 ] A similar observation was made for SAMs of amphiphilic undecenylphosphonic acid molecules on carbon steel, [ 18 ] but the authors incorrectly inferred crosslinking of the film. In fact, crosslinking was not possible because irradiation was done in the presence of oxygen, which is known to induce cleavage reactions under the conditions studied.…”

“…EA was applied on the copper surface according to the procedures proposed earlier. [5,6] As carboxylic acids are known to preferentially bind on metallic oxides, thermal oxidation of copper's surface is an important step prior to EA application. It has also been shown previously that heating of the fatty acid solution has a positive effect on the layer stability, as well as drying at higher temperatures after SAM application.…”

“…The peaks at 2850 and 2922 cm −1 are associated with the CH stretching modes of methylene groups and characterize the ordered aliphatic monolayer with alkyl chains in an all-trans configuration. [4,6,24] The peaks observed at 2871 and 2957 cm −1 are assigned to the CH stretching modes of methyl groups but are not always clearly distinguishable. These absorptions were observed in the spectra of 30 and 110 kGy samples, only sporadically in 250 kGy samples.…”

“…FAs are known to have the ability to self-assemble on a variety of substrates, including metals, by forming molecular layers on the surfaces, usually referred to as self-assembled monolayers or multilayers. [1,[3][4][5][6][7] Figure 1a is a simplified schematic of the assembly of FA on copper, where binding to the substrate by chemisorption is a mode to completely cover the surface. The driving force for the spontaneous adsorption of carboxylic acids on metals is the formation of a surface salt between the carboxylate anion and a metal cation on the surface.…”

Formation of Self-Assembled Anticorrosion Films on Different Metals

“…Special atmospheric conditions (e.g., ozone) can destroy the thiol SAM nanolayers, when the thiolat head group is transformed to sulfonate. Other researcher explained that the ozonolysis can occur under the influence of UV light at wavelength of 185 nm and 254 nm [ 57 , 58 , 59 ].…”