Do novel hybrid coatings protect aluminum alloys from corrosion?
What corrosion protection properties do three novel eco-friendly hybrid epoxy-silicon (EP-S) coatings have in comparison to commercial epoxy (EP) coatings on aluminum alloys? This question was in the centre of a research work by international scientists.
The protective properties of the coatings were evaluated by means of Electrochemical Impedance Spectroscopy (EIS), also supported by physico-chemical characterization of the coated surfaces by Fourier Transformed Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM), as well as Contact Angle (CA) and Energy Surface measurements.
Excellent barrier properties
The very high impedance (Z) values confirmed the excellent protective properties and the suitability of the novel EP-S coatings to protect 5005 aluminium substrates exposed to a simulated harsh marine environment (10% (w/w) NaCl solution), when compared with commercial EP coatings providing an adequate corrosion protection performance. Surface characterisation tests to the hybrid coatings corroborated their excellent barrier properties.
Low wettability
The comparison of the IR spectra before and after immersion test in the referred NaCl solution demonstrated the absence of water inside the EP-S coatings. Additionally, the very high water contact angle (>90°) and low surface energy values, confirmed the hydrophobic nature as well as the low wettability of the hybrid coatings. It was concluded that the addition of silane containing an amine functional group allowed obtaining a denser and more effective protective coating.
The study is published in: Progress in Organic Coatings, Volume 110, September 2017, Pages 78–85
