Multi-functional AlZr-TiO2 bilayer coatings
Matériaux, Strasbourg 19-23 Novembre
The fouling in marine environment is characterised by the development of organic matters and different types of bacteria which can accelerate the saline water effect on steel by modifying the reaction rates and the corrosion mechanism. We propose in this work a multi-functional coating consisting in an architectured material formed by an anticorrosion Al-Zr interlayer and antibiofouling TiO2 top layer. High speed steel (HSS) substrates were first coated by DC magnetron sputtering with Aluminum-Zirconium alloy 3 μm thick films containing 5 at.% Zr. Aluminum-based alloys coatings are potential candidates for galvanic corrosion protection of mechanical steel parts with the advantage of using environmentally friendly methods such as PVD. Al-Zr film is proposed as a potential candidate for providing sacrificial anticorrosion resistance of steels since it shows a good compromise between the mechanical reinforcement and the electrochemical properties. TiO2 presents photocatalytic activity and hydrophilic / hydrophobic behavior which can induced antifouling properties in order to slow down the biofouling process in the marine structures. Photocatalytic oxidation is a low cost promising technology to control fouling in submerged surfaces by production of reactive oxygen species. On the top of the Al-Zr layer, TiO2 films were deposited by atmospheric pressure Aerosol-Chemical Vapor Deposition (AACVD). This deposition technique allows to obtain nanostructured TiO2 with a high surface area and rough self-cleaning films. AACVD is a fast suitable technology for the deposition of thin films with tunable properties on large scale substrates. In this work, the architectured samples were analyzed by XRD, SEM in order to investigate its structures and morphologies. Water contact angle was used to evaluate the surface energy. Electrochemical tests in saline solution were carried out and photocatalytic activity using Orange G under UV illumination has been measured. The corrosion and biofouling behavior and performance in natural sea water were also evaluated.