Characterisation of Electroplated Gold Coatings for Dental Applications: Estimation of Thickness Using Non-Destructive Electron-Probe Microanalysis Related to Plating Time

Abstract

Objectives: This study aimed to measure non-destructively gold (Au) electrodeposited on a high-gold alloy by modulating coating time and comparing this to sputtering Au to known thicknesses. Methods: Au was electrodeposited (plated) on 11 high-gold alloy plates (A–K) at 2.8V between 20 and 220 min. Seven Au strips were sputter coated on the same alloy to known thicknesses (range 50–500 nm). Energy dispersive X-ray spectroscopy (EDS) was used to measure minimal electron energy (E0) required to penetrate Au coatings and generate x-ray signals of 1% atomic palladium (Pd) from the underlying alloy for test samples and Au strips. % Pd X-ray concentration at maximum 30 kV was also obtained. The obtained signal–thickness relationship of known Au strip thicknesses was used to calculate Au thickness on the A–K samples based on two analytical relations. Energy dispersive X-ray fluorescence spectroscopy (XRF) was used as a complementary method to ensure coating thickness estimations were accurate. Results: EDS values for all reference and unknown thicknesses were obtained and verified with XRF. Correlating these signals with the Data Analysis Software and matching with known plating times allowed estimation of Au thickness of the unknown samples (range 27–425 nm). Estimated thicknesses were shown to have a linear relationship with plating time except for samples C–D, where there was an inverted relationship. Significance: A non-destructive method for measuring electrodeposited thickness of Au on high-gold alloys related to plating time was developed and verified. There is a linear relationship to Au thickness and plating time between 20 and 220 min.