The ACFM technique was originally developed for the sub-sea inspection of offshore structures in order to detect surface breaking fatigue cracks on uncoated and coated structures. The potential of its use was recognised by maintenance engineers on and offshore and the technique was then applied to the inspection of structural and process plant in some cases together with abseiling techniques. Initially the technique was used to inspect carbon steels but since then its use has been expanded to the inspection of stainless, duplex and super duplex steels, aluminium, Monel and Inconel. It has also been used to inspect through epoxy coatings as well as standard paints and aluminium. The reliability in detection and sizing crack lengths and depths has been proven during the Probability of Detection and Sizing Trials carried out at University College London, where the technique achieved better crack detection results than MPI. The addition of up to 2 mm of epoxy coating did not affect the performance of the technique.

The manual ACFM technique is now recognised by the Certifying Authorities and the on and offshore operators of oil and gas process plant. Multi element arrays have been developed for the inspection of space vehicles and irradiated acid tanks, in the latter case to detect corrosion pitting.

In conclusion the ACFM technique is now an important tool for the inspection and maintenance engineer and has proved its usefulness in the inspection of pressurised plant.