Cleaning of Metal Surfaces

Many steps in metal processing require a thorough surface cleaning. The use of test kits and contact angle measurements are established methods to check the result of a cleaning step. However, these methods do not yield information about the cause of cleaning problems once they occur. In this case, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) can give additional information:

The details of the ToF-SIMS spectra show chemical changes on a high-grade steel surface after a cleaning process (ultrasonic bath with surfactant). Prior to the cleaning step, the surface is clearly contaminated with mineral oil and fats. Even single fatty acid residues (e.g. palmitate (255 u) and arachidate (311 u)) can be identified  in the ToF-SIMS spectrum of negatively charged secondary ions. The cleaning step leads to a considerable reduction in the intensity of the characteristic signals for mineral oil and fatty acids.

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