Detection of the early stages of degradation of coated metals is important in two distinct applications. The first is to facilitate distinction between different coatings in accelerated testing. The second is to detect or monitor degradation of a critical structure in the field.
Because high-performance coatings are very good, screening or ranking coating formulations can require a long-time, even with accelerated testing in the laboratory. It is not uncommon for an accelerated test to take three to five months. Making the test more aggressive can reduce the time required, but there is always a concern that different degradation mechanisms are involved compared to service conditions. If this is the case, the testing is not valid. Thus, there is a need for corrosion sensors that can detect and quantify the early stages of corrosion. There is a further need to be able to directly compare the degradation in an accelerated test to that occurring during service.
The second application involves health monitoring of critical structures in the field. Periodic inspection of both inaccessible and accessible areas of an airplane or other structure to track corrosion from the early stages would enable condition-based maintenance. In other cases, quick spot inspection of structures are desired without the need for permanent attached sensors or long-term exposure of sensors.
In-Situ Sensor to Detect Moisture Intrusion and Degradation of Coatings, Composites, and Adhesive Bonds, G.D. Davis, C.M. Dacres, and L.A. Krebs, DACCO SCI Inc.