The cost associated with maintenance and field replacement of military assets is often reduced by the application of temporary coating systems that protect the military vehicles against corrosion. The performance of these coatings can be assessed using coating degradation sensors. This paper addresses the laboratory studies of an impedance based coating degradation sensor that utilizes wireless, mote based technology. The ability of the coating degradation sensor to assess coating failures in simulated coastal environments is demonstrated. The results are compared with those of field exposure at Daytona Beach, FL. The effects of the sensor design and measurement parameters on the sensitivity of the sensor are explored. Examples of the sensor output to determine failures of corrosion preventive compounds (CPCs) in case of boldly exposed surfaces and occluded sites will be presented.
The US Marine Corps vehicle fleet is subject to severe corrosion as a result of harsh operational mission environments. In order to reduce the costs associated with depot maintenance and field replacement, temporary coating systems are used to protect against corrosion. Several corrosion preventive compounds (CPCs) have been employed successfully by the US Marine Corps to mitigate corrosion1. CPCs are oils, greases or resin-based film formers that form a protective barrier, which in turn limits the contact of moisture with metallic surfaces2. As temporary coatings, CPCs need to be reapplied periodically. However, no established methodology exists to assess the coating performance or need for reapplication. This results in increased inspection costs and/or over conservative reapplication intervals. Moreover, the USMC is currently seeking Condition Based Maintenance (CBM) strategies in order to reduce inspection costs while minimizing the risk of equipment damage and/or failure due to corrosion. CBM technologies employ real-time data to prioritize and optimize maintenance resources. They utilize sensors, models and automated reasoning to monitor the operation of equipment (condition monitoring), and determine the appropriate maintenance tasks prior to impending failure. It is Department of Defense policy that CBM be “implemented to improve maintenance agility and responsiveness, increase operational availability and reduce life cycle total ownership costs”3. Sensors present an attractive option for the field monitoring of corrosion protection systems for the CBM corrosion strategy. There are, however, several significant challenges to be overcome. For example: The condition of individual vehicles as well as that of the overall fleet needs to be assessed with a limited number of sensors. The system must be capable of making autonomous recommendations regarding corrosion maintenance, i.e., it needs to provide (1) robust data acquisition, (2) wireless data transmission and (3) data interpretation capabilities. Mote-based sensor technologies are capable of wireless data transmission. They are also equipped with an on-board operating system allowing the direct, localized control of each sensor resulting in efficient data collection and transmission as well as power conservation. The data collected by the mote based sensors are transmitted to a data hub, where they can be processed and analyzed using Bayesian technique. The technique applies logical and probabilistic rules to develop a so called Bayesian Network.