Corrosion Protection and mechanical performance of SiO2 films deposited via PECVD on OT59 brass

SiO2 layers deposited on OT59 brass substrate (BS) via Plasma Enhanced Chemical Vapour Deposition (PECVD) were tested to examine their corrosion performance and nano-mechanical characteristics. The electrochemical tests were carried out in a standard very aggressive solution (aerated 1N H2SO4 at 25°C) by means of DC (Tafel curves) and AC (Electrochemical Impedance Spectroscopy - EIS) techniques. After a week (168h) of immersion time the best PECVD treatment was reached by a layer thickness of 1950 nm, even if thinner coatings had a non negligible effect. The hardness and the elastic modulus of the films and the BS were measured by load-depth nano-indentation tests. The results highlighted a significant increase in the Berkovich hardness of annealed coated samples compared to that of the bulk brass. The excellent protection was also certified after examining some industrial objects treated by means of the same industrial PECVD process.