In-situ detection of single particle impact, erosion/corrosion and surface roughening

Abstract

Particle impact is technologically important and can cause significant damage to a surface. Detecting the approach and impact of a particle would give key information on the process. High-speed imaging of this process gives information on a particle's velocity and movement but does not answer key questions relating to changes in electrochemical properties of a surface caused by the resultant damage on impact. Furthermore, it is difficult to apply in non-transparent media. To gain this key information, we have deployed a high-speed electrochemical impedance technique with the ability to determine the uncompensated resistance, Faradaic current and effective capacitance of an electrode. This technique has a time resolution of 1.25 μs. Individual impacts of sand particles in a fluid jet (jet velocity ~4–5 m s−1) are used to cause erosion/corrosion of an aluminium interface. Surface properties are shown to change after individual particle impacts, which is preceded by the electrochemical detection of the particle as it approached the solid/liquid interface. For the first time, the in-situ roughening of the electrode surface is reported for a single particle impact. A link between the effective mass loss of the electrode and the overall surface erosion is shown, with an equivalent roughening rate of 8.5 F g−1 as determined from the data. This study shows how individual sand particles, and the damage they cause to an interface, can be detected with high precision and new insight. This will improve our understanding of erosive environments.