Silver-based vitreous enamel coatings: Assessment of their antimicrobial activity towards Escherichia coli and Staphylococcus aureus before and after surface degradation

Porcelain enamel coatings are silica-based inorganic coatings, which are successfully applied to different kind of metallic substrates in applications where high chemical resistance and corrosion protection are needed. In addition, these coatings meet very modern criteria of durability and environmental sustainability. For this reason, they could be a valid solution for application in healthcare settings and public spaces, where cleaning and disinfection are frequently required. The possibility to produce durable antibacterial enamel coatings would broaden their application areas and represent a possible solution to address the spread of pathogens in many public spaces. The main of this work is to develop innovative antibacterial enamel coatings with the addition of silver-based additives (AgNO3) and test their antibacterial efficacy in operando conditions (i.e., after chemical and mechanical degradation) by exploiting antibacterial assays according to the ISO 22196:2011 standard. Three different sample types will be taken under consideration: the reference sample, and the sample with the addition of 1 wt% AgNO3, and the sample with the addition of 2 wt% AgNO3. The surface properties and the microstructure of the samples will be deeply investigated by surface sensitive techniques, optical microscopy, and electron microscopy observations. The antimicrobial efficacy of these samples will be tested against Escherichia coli and Staphylococcus aureus both before and after chemical/physiochemical degradation.