Eddy current evaluation for thickness loss estimation of aluminum alloys used in aircraft structures

Aluminum alloys are commonly used in the aircraft industry but it tends to corrode and needs to be inspected properly. Eddy current testing is the widely used non-destructive testing (NDT) for aircraft metals. This research studied estimating the thickness loss due to corrosion in an aircraft aluminum sheet metal. The Al1100, Al2024, and Al7075 were 2 mm thick. Aluminum sheet metals were used to create artificial damage in hydrochloric acid. The thickness loss due to corrosion was inspected with eddy current testing (ET) and compared with the measurement from the coordinate measurement machine (CMM). The results showed that the thickness loss due to corrosion could be estimated using the eddy current skin depth frequencies. However, in the practical application, the skin depth could be guessed from the corrosion rate which could reduce the inspection time. In this research, the corrosion rate was measured by using potentiodynamic measurement. It can be used for estimating the thickness loss for an appropriate inspection interval.