Seawater is used for a number of applications and systems aboard ship. The majority of fire main systems use seawater, including the fire mains for the flight deck (on carriers) and any decks above. Larger ships in the fleet also utilize seawater in several auxiliary machinery systems including nuclear powered propulsion plants that use the seawater as a cooling medium. In addition, on-board A/C plants also use seawater-in "chilled water systems"-as heat exchangers. Each of these systems is compartmentalized, allowing them to function alone or, when another system is damaged or requires maintenance, to act as a backup.

All of the seawater systems incorporate piping of various sizes according to the volume and flow of water necessary. As the systems branch throughout the ship, the size of the piping decreases increasing the velocity of the water flowing through the pipe. Each piping system utilizes valves, strainers, check valves, and other pressure regulating components to maintain the required seawater flow rates and pressures. Because these components are manufactured using materials similar to the piping itself, galvanic corrosion is not ordinarily a problem. However, because flanges, used at the point where piping connects to a piece of equipment, are generally manufactured from dissimilar materials, crevice corrosion remains a persistent concern. Since the crevice corrosion is almost always confined to within the crevice itself, the pipe joints must be periodically disassembled and visually inspected for evidence of crevice corrosion. This process is time consuming and, consequently, expensive.

CORMIT Technology

The goal of the CORMIT project is to develop a state-of-the-art crevice corrosion detection and mitigation technique for the ship seawater pipe system components. The KBSI team, led by Dr. Paul Koola, is applying their expertise in artificial neural networks (ANN) to develop multi-fusion software technology that integrates a variety of data from a number of different sensors. This give users a more nuanced perspective of corrosion build up in the piping system.

Because of the awkward geometry of the pipe systems, the real time monitoring of crevice corrosion using traditional monitoring techniques was not possible. Following a careful study of the piping system and traditional monitoring technologies, we determined that crevice areas had to be directly monitored. KBSI's work in Phase I of the project addressed this difficulty by developing an instrument O-ring and gasket with multiple sensor integration capability for multi-sensor fusion analysis. We embeded several minitiaturized electrodes within O-ring and/or gaskets for monitoring the impedance of crevice surface, pH of crevice solution, solution resistance, and dissolved oxygen of crevice solution. These sensors, when used concurrently, yielded enough information to develop mitigation techniques based on impressed currents.

The second step focused on developing condition based maintenance (CBM) software for detecting the onset of crevice corrosion. This software has the novel capability to detect crevice corrosion of varying severity, incipient crevice corrosion in the presence of significant sensor noise, crevice corrosion conditions for which no prior information nor sensor data is available.

The goal of KBSI's work in Phase II is to develop state-of-the-art software that performs multi-sensor fusion on crevice corrosion detection sensors. This involves developing a centralized monitoring device (CMD) with distributed intelligent corrosion sensing and mitigation (ICSM) hardware/software to detect and mitigate crevice and galvanic corrosion in seawater pipe components. The CDM displays the corrosion status for the seawater components. The ICSM component developed in the Phase II project will have the capability to sense and mitigate crevice corrosion for seawater components like flanges, valves, and strainers. Using the data gathered by the ICSM, the CDM displays the corrosion status for the seawater components.

Clearly the CORMIT technology has applications beyond the Navy's use. A market for corrosion mitigation products already exists for the shipping and offshore platform industries. Additional CORMIT commercial application opportunities exist in power plants and the oil and gas refining industries, where large shore based facilities also use seawater as a cooling medium.