A solid-contact Mg2+ ion-selective microelectrode (ISME) usually consists of a carbon fiber coated with conducting polymer, such as electropolymerized 3, 4 ethylenedioxythiopene (PEDOT), in contact with the ion-selective membrane. PEDOT is typically electrochemically deposited onto the carbon fibers from rather expensive ionic liquid based dopants. Herein, Mg2+ ISMEs were assembled using a commercially available Mg2+ ionophore-containing solution and PEDOT electrochemically deposited from sodium p-toluenesulfonate, thus providing a simple and inexpensive method to develop Mg2+ ISMEs. The ISME fabricated by this procedure is successfully able to respond to Mg2+ ion concentrations arising from pure Mg during free corrosion and also galvanic corrosion (when Mg is coupled to pure iron). (C) The Author(s) 2018. Published by ECS.