Being a commercial test house and not a research centre means that methods of identification are strictly defined within a fixed budget. The analysis tools used will depend on the type of deposit and the relevant information that is required by the Client. Scanning electron microscopy with X-ray diffraction (SEM-EDX) is usually used in the first instance. This technique will identify percentage content by element for carbon and above in the periodic table.
This technique is therefore ideal for identifying and semi-quantifying the presence of any heavy metals present in the deposit (toxicity). The very high resolution of the SEM (0.05 micron) enables detailed examination of the deposit structure. Examples: individual bacteria cells, silica diatom (algae) skeletons, crystalline structures, fibre types can all be identified. The white light photograph on the left, shows a gold coloured surface contaminant on a stainless steel part.
SEM/EDX analysis confirmed that the coating was only two microns thick. SEM/XPS analysis identified this thin gold coloured, (under white light) coating as iron sulphate, (the XPS sulphur trace is given on the right).
Deposit testing can also include failure analysis and the identification of the cause for the failure. The two pictures below detail a ductile fracture of a valve due to de-zincification caused by water attack.