H. Weiland, J. Moran, F. Bovard, Alcoa Incorporated, Alcoa Center, PA; D. Grundy, Jentek Sensors, Inc., Waltham, MA; V. Zilberstein, I. Lorilla, D. Schlicker, N. Goldfine, JENTEK Sensors, Inc, Waltham, MA
Joints of electrochemically similar and dissimilar materials are susceptible to hidden corrosion that is detectable only with NDE equipment during scheduled inspections. Material loss due to hidden corrosion reduces residual strength of the structure. As a part of a Structural Health Monitoring concept, it is necessary to develop technology capable of detecting hidden corrosion at faying surfaces in difficult-to-access locations, e.g., on aircraft at intervals shorter than specified in maintenance schedules. For structural members, early detection and characterization of material loss using sensor arrays is preferable to the use of electrochemical methods that measure local corrosion reaction parameters but do not provide actual metal loss. MWM-Array eddy current sensors were mounted on the outside of lap joints made from Al 2024-T3511 of 1.5 mm gauge with a 7055-T76511 attachment in one set of joints, a 2029-T8511 attachment for another set of joints, and a GLARE attachment with exposed graphite layer towards the joint interface for the third set. The surface of the parts were not coated, however, the outer surface of the assembly was covered with electroplaters tape to ensure corrosion occurring only under the footprint of the sensor. These lap joints were exposed to an EXCO solution and the corrosion process was continuously monitored using MWM-Array sensors. The data successfully determined the material loss from hidden corrosion at material losses of 2 percent of the thickness onwards at a sufficiently high accuracy. Future plans include long duration tests with intermittent data collection and on-aircraft tests.
Summary: N/A
