Corrosion mapping by ultrasonics is a nonintrusive (noninvasive) technique which maps material thickness using ultrasonic techniques.
Variations in material thickness due to corrosion can be identified and graphically portrayed as an . The technique is widely used in the oil and gas industries for the in-service detection and characterization of corrosion in pipes and vessels. The data is stored on a computer and may be color coded to show differences in thickness readings.
Corrosion may be mapped using Zero degree ultrasonic probes, an Eddy current array and/or Time of flight detection methods. The book Nondestructive Examination of Underwater Welded Structures by Victor S. Davey describes a "fully automated dual axis robotic scanner used for corrosion mapping normally using a single zero degree compression probe scanned in a raster pattern over the area of interest." He also goes on to explain that "typically a 4 mm by 4 mm raster" is used.
References
Computer modelling for the prediction of the probability of detection of ultrasonic corrosion mapping Authors: Burch, S F; Stow, B A; Wall, M Eddy current array probe for corrosion mapping on ageing aircraft AIP Conf. Proc. 509, pages 489–496; 8 pages) REVIEW OF PROGRESS IN QUANTITATIVE NONDESTRUCTIVE EVALUATION: Volume 19 Date: 25–30 July 1999 Location: Montreal (Canada) Rémi Leclerc and Rock Samson Pipeline Corrosion and Cracking and the Associated Calibration Considerations for Same Side Sizing Applications Ginzel, R.K. & Kanters, W.A. Eclipse Scientific Products Inc, Williamsford, Ontario, Canada https://web.archive.org/web/20160304064220/http://www.turkndt.org/sub/makale/ornek/Pipeline%20Corrosion%20and%20Cracking%20and%20the%20Associated%20Calibrati.pdf Improved plant availability by advanced condition based inspections Harry J.M Hulshofa, Jan W Notebooma, Paul G.M Welberga, Leo E de Bruijnb KEMA Nederland BV, P.O. Box, 9035 6800 ET Arnhem, The Netherlands Benelux Generation N.V., Rotterdam, The Netherlands