Electrodeposition and Characterization of Thin Film of Black-Gold

Abstract

White gold and yellow gold are the most common types of gold colours used in jewellery making. Anyway lots of other colours of gold are also possible to achieve by electroplating and some of these colours may surprise. At the moment the market is gaining more and more interesting in purple gold, or black gold and even blue gold. There are two electrochemical deposition processes used to obtain such colours: the first one is by formation of special gold metal compounds also referred to as Intermetallic Compounds. The second process is by forming a surface coating on gold, also referred to as Patination of Gold. Here we present some methods to prepare Black gold thin films. Amorphous carbon is used at times during Plasma Assisted Chemical Vapour Deposition process. Controlled oxidation of carat gold containing chromium or cobalt can also be used to yield black gold. We investigate mainly thin films obtained by Electrodeposition processes. Electrodeposition using black Rhodium or Ruthenium added to gold electroplating solution is one way. Electroplating solutions containing Ruthenium give a slightly harder black coating as compared to electroplating solutions containing Rhodium. We present some electrochemical results about the formation of thin films of black gold and their morphological characterizations by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). We’re going also to evaluate a correlation between films electrodeposited from different plating baths and corrosion resistance of the films themselves.