Coating Analysis
What is the “surface”?

CSMA specialises in surface and interface analysis but what is “the surface”?
Traditional surface analysis techniques such as SIMS (Secondary Ion Mass Spectrometry) and XPS (X-Ray Photoelectron Spectroscopy) have a sampling depth of between 0 and 10nm whilst depth profiling SIMS and XPS can investigate the outer microns of a sample, particularly suitable for layered systems.

However, when a coating needs identifying but is thought to be a homogeneous layer several microns thick techniques such as SEM/EDX (Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis) and ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infra red) are often more suitable than SIMS and XPS. With sampling depths of between 1 and 3 microns the information gained by SEM/EDX-quantified elemental, and ATR-FTIR-organic groups present, can often be enough to identify the coating.

An example
CSMA was recently approached to fingerprint a specific coating product which was thought to be a commercially available lacquer compound.
The coating was analysed by SEM/EDX with the resultant high-resolution images showing that the surface was cracked and had numerous particulates present and the EDX data identifying the particulates as well as indicating the presence of an organic lacquer coating with small areas of the substrate also identified i.e. the coating was incomplete. Due to the indication of the presence of organic species ATR-FTIR was undertaken. As with traditional FTIR ATR-FTIR provides detailed organic information but with the ATR technique the information is only from the outer 3 microns not from the bulk of the material.

The combination of these techniques led to the identification of the chemical composition of the lacquer which in turn led to the commercial product.

For further information please contact Justine Bentley, e-mail: justine.bentley@ceram.com, tel: +44 (0)1782 764269.