Development and evaluation of coatings and surface conditions on steel for antibacterial and easy-to-clean properties

This project aims to develop hygienic surfaces and coatings on steel, in order to reduce microbial proliferation and related contamination, and to provide easy-to-clean or self-cleaning surfaces. With this objective in mind, coatings/treatments with antimicrobial and easy-to-clean properties were produced by sol-gel, magnetron sputtering, organic coating application, ion implantation and plasma polymerisation techniques, on stainless steel and galvanised and polyester coated steels. The developed surfaces were characterised according to composition, morphology, surface roughness and water contact angle. The silver-containing coatings/treatments showed antibacterial activity. No evidence was detected of antimicrobial activity for TiO2 coatings, suggesting no photocatalytic activity of TIO2 under test conditions. No influence of biocide agents in corrosion performance was observed, except in the Kesternich test for silver-implanted stainless steel. Accelerated laboratory tests simulating exposure media and service conditions were successfully set up, namely the carbon black test and food staining test. The coatings/ treatments were exposed to simulated environments of outdoor industrial, food processing, and road tunnel and field tests in a sewage water plant, HVAC, food-processing environment and outdoor building exposure were carried out. Excellent cleanability and self-cleaning behaviour was observed for sol-gel coatings, mainly attributed to the highly hydrophilic surfaces achieved with these coatings. The sol-gel coating with TiO2 and Ag, the amorphous TiO2 coating with Ag by magnetron sputtering, Ag implantation and V3+B6 polyester coating modified with silver glass/zeolite were selected as the coatings/ processes with best functional performance. The functional long-term durability as well as the mechanical properties of the coatings should be further studied