Corrosion studies in high-temperature high-pressure aqueous environments, and in particular electrochemical corrosion measurements in these environments, are again becoming more important for a number of industrial applications. Reliable and accurate electrochemical measurements in high-temperature high-pressure aqueous systems (i.e. up to ca. 300 degrees C) are, however, not straightforward. Especially the stability of so-called 'internal' reference electrode systems or the accuracy of 'external' reference systems continues to pose major measurement problems. In this paper we will present a brief state-of-the-art, and we will demonstrate the possibility of transforming the huge amount of correction data for external reference electrode systems into one simple analytical expression, at least for neutral and alkaline solutions. For acidic solutions, there is a small deviation. Precisions of the order of +/- 5 to 15mV (depending on the temperature) can generally be obtained, which should be sufficient for applications like corrosion monitoring, redox potential measurements, etc. (C) 2016 Elsevier Ltd. All rights reserved.