High-accuracy ultrasonic corrosion rate monitoring

Corrosion is one of the most pervasive degradation mechanisms of engineering infrastructure. In the petroleum industry, it is particularly challenging because crude oils contain a large amount of corrosive substances. Ultrasonic testing with permanently installed transducers is widely used for online corrosion monitoring in the field. 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 approximately 40 nm can be maintained over the period of a day. 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 showed that wall loss rates of the order of 0.1 mm/y to 0.2 mm/y can be detected within 1 hr to 2 hr. 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.