Photocatalytic TiO₂ and Doped TiO₂ Coatings to Improve the Hygiene of Surfaces Used in Food and Beverage Processing: A Study of the Physical and Chemical Resistance of the Coatings

TiO₂ coatings deposited using reactive magnetron sputtering and spray coating methods, as well as Ag- and Mo-doped TiO₂ coatings were investigated as self-cleaning surfaces for beverage processing. The mechanical resistance and retention of the photocatalytic properties of the coatings were investigated over a three-month period in three separate breweries. TiO₂ coatings deposited using reactive magnetron sputtering showed better mechanical durability than the spray coated surfaces, whilst the spray-deposited coating showed enhanced retention of photocatalytic properties. The presence of Ag and Mo dopants improved the photocatalytic properties of TiO₂ as well as the retention of these properties. The spray-coated TiO₂ was the only coating which showed light-induced hydrophilicity, which was retained in the coatings surviving the process conditions.