Electrochemical effects on rock drilling.
Engelmann WH; Watson PJ; Tuzinski PA; Pahlman JE; Khalafalla SE
J Electrochem Soc 1988 Apr; 135(4):1043-1044
A strong correlation was found between drilling performance and the zeta potential at the rock-solution interface. Maximized drilling performance occurred where the ionic concentration produced a zero point of charge (zpc). At the rock zpc, the zeta potential is also zero. A model based on correlations between the electrical double layer profiled in the rock interfacial layer and lippmann's electrocapillarity curve is proposed to account for the observed phenomena. At the zpc concentration, the rock interfacial tension is maximized; drilling enhancement is also maximized, possibly because the rock is weaker in tension than in compression. Surface tension reducers are efficient in chemical crack propagation. Taking drilling as an activated cracking with catastrophic growth of microcracks into more destructive ones, it is possible that the interfacial tension, or surface energy, must first reach a critical tension before fragmentation occurs, with an overall lowering of the interfacial tension. This distinction between the kinetic process of drilling and the thermodynamic transition of crack formation explains why an increase in interfacial tension can facilitate drilling by lowering the energy barrier for rock fragmentation.
Mining-industry; Mineral-processing; Metals;
Author Keywords: rocks; electrochemistry; surface tension; electrokinetic effects
OP; Journal Article
Journal of the Electrochemical Society