Direct observation of electric charges at solid/liquid interfaces with the pressure-wave-propagation method

Abstract Development of intrinsic electric charges at solid/liquid interfaces is still not fully understood and may generate large industrial damages by electrostatic discharges due to flow electrification. The pressure-wave-propagation (PWP) method is used to study solid/liquid interfaces in still and flowing conditions. Experimental results are shown with aluminum, brass, copper or pressboard in contact with demineralized water, salted water, glycerol or mineral oil. Salted water presents larger charge extent than expected. In still conditions with glycerol, copper gives more charges and pressboard has the largest charge extent. In flowing conditions, signal decrease seems attributed to physico-chemical time constant.