Release of metallic elements by food simulants from hardmetal coatings

Thermally sprayed hardmetal coatings are commonly applied to protect components of machines and devices from wear. This includes also machinery in food industry. Surprisingly, there is no data in the literature dealing with the release of metallic elements from wear resistant coatings to food. It was the task of the current investigation to develop a suitable analytical methodology and to make a first evaluation for state-of-the-art coatings. Thus, the release of metallic elements Cr, Co, Ni and W depending on time, from standard coating compositions WC-10Co-4Cr and Cr₃C₂-NiCr into simulants (artificial tap water, citric acid, and ethanol) was investigated. The coatings were deposited by HVOF using a DJH 2700 gun operated with propane with an industrially optimized spray parameter set on stainless steel (1.4301) substrate. Coatings were characterized by XRD and SEM of the cross-sections. These samples were immersed into the food simulants and the release of the metals was studied by flame-AAS. In order to investigate the compositional changes during the spray process, feedstock powders as well as detached and milled coatings were studied for comparison with ICP-OES. The release of the metallic elements was comparatively stuidied and will be presented.