The main geophysical application of spontaneous potentials (SP) anomalies, i.e., electrical signal generated by hydroelectric coupling, is the mapping of hydrothermal zones. Laboratory studies of hydroelectric coupling as a function of temperature are scarce, because of experimental difficulties. Up today experiments carried out by Ishido and Mizutani <1981> with quartz-Al-K-NO3 system for temperatures ranging from 20¿C to 80¿C are not well understood. In this work, we show that Ishido and Mizutani <1981>'s solutions are oversaturated with aluminium, and that the precipitation of Al(OH)3s is expected. Triple Layer Model (TLM) calculations for a gibbsite-KNO3 system can account for Ishido and Mizutani <1981>'s measurements. These results highlight that (1) the precipitation of a secondary mineral can hide the electrical properties of the primary rock; (2) the geochemical fluid surveys should be taken into account to grasp the interfacial processes (precipitation/dissolution), and to interpret the SP measurements in the field.