Magnetic measurements of the response of corrosion activity within aircraft lap joints to accelerated corrosion testing

We have demonstrated the ability of Superconducting QUantum Interference Device (SQUID) magnetometers to qualitatively monitor electrochemical activity within lap joints removed from actual aircraft. This work lays the foundation for quantitative measurements of corrosion rates within occluded structures. In this study, a SQUID magnetometer was used to examine hidden corrosion activity within lap joints removed from ageing KC-135 aircraft. During exposure, we imaged each specimen every 60 minutes. We designed the protocol to expose each lap joint specimen to a range of increasingly corrosive exposure sequences. The results obtained from this protocol show that there is a clear relationship between corrosivity of the environment and the activity generated within the lap joint. Over a range of increasing corrosive environments, the activity generated shows significant increases with each step. This technique allows us to determine non-invasively the corrosivity of the chemical environment already existing inside the lap joint relative to environments of known corrosivity.