Case Study – Comparison of penetrant inspection and eddy current testing on a corroded test sample


April 2016



Our customer is an aerospace MRO (maintenance, repair and operations) company based in the UK, with an aerospace training college. Part of their training includes teaching students about NDT capabilities within the aerospace sector, identifying the strengths/weaknesses and applicability of different NDT inspection techniques.



One of the test samples used for training purposes is an aluminium component from a heavily corroded Fokker 50 main undercarriage The trainees are set a challenge to use different NDT techniques to find a single crack within the corroded test sample.

The trainees found that using eddy current testing to interpret the test results proved difficult due to the intensity of corrosion. The eddy current crack screen representation was masked by the heavy corrosion indications, which means it would be easy to miss a fatigue crack within a heavily corroded area.



The test component was inspected using ZYGLO® ZL-60C, Magnaflux  EMEAR’s  water-washable  fluorescent  Level  2 penetrant. ZL-60C is ideal for inspections where a medium sensitivity penetrant is needed, such as general engineering components.



Under UV(A) light, ZL-60C gave a clear visual indication of the fatigue crack in the test component. Using the water wash process, the crack was clearly differentiated from the background corrosion.


“The simplicity of penetrant inspection using ZYGLO ZL-60C in such a situation clearly highlighted its benefit over eddy current testing, where it is much more difficult to differentiate between defect signals and geometry effect signals.”

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