Nanostructured coatings approach for corrosion protection

• Published in: Progress in organic coatings 2003-09, Vol.47 (3), p.416-423
• Main Authors: Voevodin, N.N, Balbyshev, V.N, Khobaib, M, Donley, M.S
• Format: Article
• Language: English
• Subjects: Applied sciences; Coatings. Paints, varnishes and inks; Exact sciences and technology; Film formation and curing, properties, testing; Nanostructured coatings; Polymer industry, paints, wood; Self-assembled nanophase particle; Sol–gel
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/S0300-9440(03)00131-0

Nanostructured surface treatment coatings based on the Self-assembled Nanophase Particle (SNAP) approach were investigated as potential replacement for chromate-based surface treatments on aircraft aluminum alloys. In the traditional sol–gel method, hydrolysis-condensation processes are followed by condensation polymerization upon film application. This process sequence provides a low temperature route to the preparation if thin coatings which are readily applied to most metallic substrates. The recent discovery of a method of forming functionalized silica nanoparticles in situ in an aqueous sol–gel process, and then cross-linking the nanoparticles to form a thin film, is an excellent example of a nanoscience approach to coatings. This Self-assembled Nanophase Particle (SNAP) process can be used to form thin, dense protective organic surface treatment coatings on Al aerospace alloys. The ability to design coating components from the molecular level upward offers tremendous potential for creating multifunctional coatings. The important components of Al alloy corrosion inhibition by chromate are storage and release of Cr VI species, inhibition of cathodic reactions (primarily oxygen reduction), and inhibition of attack at active sites in the alloy. Unlike chromate-based treatments, current SNAP coatings provide barrier-type corrosion resistance but do not have the ability to leach corrosion inhibitors upon coating damage and minimize corrosion of the unprotected area. In this study, organic inhibitors were tested for corrosion protection of aluminum alloys in combination with the (SNAP). Scanning Vibrating Electrode Technique, anodic polarization, electrochemical impedance spectroscopy, and salt spray test were used to study this new approach for chromate replacement.