Zr-based coating for the prevention of silver tarnishing

Abstract

Purpose – This work aims to focus on evaluation of the ability of cathodically deposited ZrO2-based coatings to stabilise the surface of silver against tarnishing caused by S2−-based species and comparison of these coatings with Cr oxide-based coating. Design/methodology/approach – The coatings were evaluated using inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), impedance spectroscopy (EIS) and galvanostatic reduction of specimens exposed to H2S vapours. Findings – The kinetics of deposition were studied and optimum conditions for coating formation were determined. The options of manual application suitable for practical use were studied also. Zr specimens showed better barrier properties than did a chromated specimen. The best properties were observed on a specimen with a manually fast-applied coating. However, Zr coating does not provide as good protection from tarnishing as chromate. The structure of the Cr coating contains species of chromate that oxidize species of S2−. Originality/value – The paper provides new information regarding the anticorrosive properties of cathodically deposited ZrO2 coating as an alternative to Cr coating for the preservation of silver surfaces.