New Calibration Method for Kelvin Probe in Changing Humidity Conditions

Abstract

The use of the Kelvin probe (KP) to determine E corr values is based on the relationship E corr = const. + ΔΨ (with ΔΨ = measured value of the KP and const. = constant). The constant const. is determined by calibration above a reference sample with known E corr . It has been shown that the constant const. can vary by up to 172+/−18 mV with a probe of nickel and 178 μ m probe diameter, when the relative humidity RH varies between 42% and 98%, which must be taken into account when making measurements under changing climatic conditions. It has been shown, theoretically and experimentally, that the RH at the probe tip 40 μ m above a saturated salt solution is nearly equal to its critical relative humidity. An experimental procedure is proposed to determine the dependence of const. on RH. For this purpose 4 Cu/saturated Cu-salt half-cells are used. Additionally, a method is proposed to measure the critical relative humidity of a saturated salt solution using KP.