Ultrasonic testing with permanently installed transducers is widely used for online corrosion monitoring in the field. In this paper, a carefully optimized ultrasonic corrosion monitoring technique for performing measurements in the laboratory is presented. It is shown that for thickness measurements of a 10 mm steel component, a repeatability of ∼40 nm can be maintained over the period of a day. The technique has been applied to monitoring the wall losses of a steel sample during driven and free corrosion experiments. All ultrasonic wall loss measurements reported have been validated by optical surface profile scans and, where possible, by analytical predictions based on Faraday’s law. Further analysis of the results shows that wall loss rates of the order of 0.1 mm/y to 0.2 mm/y can be detected within 1 h to 2 h. This state-of-the-art laboratory technique is highly accurate and responsive, and possesses the potential for becoming a powerful alternative corrosion assessment tool that is convenient to use.