%0 Journal Article
%T Corrosion Protection of AA7075 Aluminium Alloy by Trimethoxy-Silanes Self-Assembled Monolayers
%A Rodrigo S. Neves
%A Daiane P. B. Silva
%A Artur J. Motheo
%J ISRN Electrochemistry
%D 2013
%R 10.1155/2013/142493
%X This study presents electrochemical data concerning the aluminium alloy AA7075 surface modified by self-assembled monolayers (SAMs) of octadecyl-trimethoxy-silane and propyl-trimethoxy-silane. Polarisation curves have shown SAMs blocking effect, as they partially block the oxygen reduction reaction and displace the corrosion potential to positive values. Electrochemical impedance spectroscopy experiments have suggested that the protective effect comes from the oxide layer stabilization by the organic monolayers, which block the corroding species diffusion to the surface. These results show the potential of using methoxy-silanes SAMs as corrosion protective coatings; however, they are also indicative of the superior octadecyl-trimethoxy-silane protective characteristics. 1. Introduction The corrosion protection of aluminium alloys is a very important topic in the electrochemistry and engineering fields, since these materials are used in different industrial areas and undergo localized corrosion [1, 2]. As an example, about a decade ago the US Air Force had showed interest in the development of aluminium alloys protective coatings with at least 30 years lifetime before maintenance [3]. In this context, much attention has been dedicated to the AA7075 alloy corrosion behavior [4每10], since this material is extensively used in aerospace and military industry due to its good mechanical performance and low density. In order to improve the aluminium mechanical properties, this alloy contains zinc (5.1每6.1ˋwt%), copper (1.2每2.0ˋwt%), and magnesium (2.1每2.9ˋwt%) as its main alloying components. The presence of such allowing elements results in the formation of intermetallic particles during the casting and homogenization processes. From an electrochemical standpoint, copper and zinc rich intermetallics are cathodic to the aluminium matrix, hence promoting the dissolution of aluminium, while the magnesium rich ones are anodic to the matrix and undergo dissolution [11]. This mechanism favours the occurrence of localized corrosion processes, hence making the development of specific corrosion protection technologies a subject of continuous interest. In the scope of new corrosion protection methods for aluminium alloys, the interest in the electrochemical properties of such materials modified with self-assembled monolayers (SAMs) has grown in the recent years [12每14]. This interest is a consequence of the potential application of SAMs as corrosion protective coatings as a substitute for the typical chromium conversion coatings [13每15], which are good protective
%U http://www.hindawi.com/journals/isrn.electrochemistry/2013/142493/