However, the corrosion protection and permanent barrier properties for metallic substrates such as aluminium can only be provided if the DLC coating contains metallic anodic or cathodic nano contacts that prevent the metallic substrate from corrosion.
In the present project ProBar the PE-MOCVD (plasma enhanced metal organic chemical vapour deposition) process has been developed and improved for industrial applications in food packaging. Excellent protection for aluminium foils against aggressive environment have been achieved and as a result, the PBA containing lacquers (thickness up to 1 mm) can be substituted by the sustainable and inert DLC layer (about 50 nm thin) doped with less than 2 mg of metallic nano contacts per meter square.
The DLC coated aluminium foils have been exposed to 0.1 M NaCl and 50% acetic acid solutions up to 27 days without being damaged. The oxygen permeability has been reduced up to 96 % compared to the uncoated PET-film, independent of the climate conditions. A global migration has not been observed for the best diffusion barrier coating during exposure to organic solutions for 10 weeks. However, the aluminium substrate was attacked in an aqueous solution at pH 1.5 after 7 days.