Methods and systems for monitoring material loss in a downhole environment arising from corrosion and/or erosion include placing a downhole sensor in a borehole. The resistance of the downhole sensor is measured using a four-probe resistance technique in which a power source is provided at two electrodes of the downhole sensor and voltage is measured at two voltage taps. A rise in voltage over time indicates loss of conductive material on the downhole sensor. The conductive material on the downhole sensor may be formed to provide discrete voltage increases for improving reliability of material loss and/or rate of material loss resistance measurements.