Corrosion mapping is an ultrasonic (UT) technique that maps and identifies changes in material thickness caused by corrosion. Corrosion is the destruction of metallic materials by chemical (or electrochemical) attack. This is usually caused by the environment (mainly water), but sometimes by another substance. There are many types of corrosion.
Uniform corrosion that spreads evenly over the entire surface
Pitting with uneven, small-depth areas (holes).
Exfoliation corrosion that progresses along a layer of elongated grains
Intergranular corrosion that grows along grain boundaries
To perform corrosion mapping, automated or semi-automated scanners are used to scan critical components or infrastructure using a variety of ultrasonic techniques such as pulse echo, eddy current and phased array (PAUT). Corrosion mapping is widely used in the oil, gas, and nuclear industries to inspect pipelines, pressure vessels, storage tanks, and nuclear reactors. Corrosion mapping using a conventional UT probe offers a simple solution but can be a time-consuming method as the probe must be scanned in both directions across the test surface. Using a coarser resolution improves scanning speed but reduces resolution and can miss small clues such as pits. Alternatively, the PAUT probe is faster and can cover a larger surface area, which can significantly reduce scan time. Collecting high-resolution data at faster scan speeds improves the probability of detection (POD), improves imaging, and improves defect characterization.
