TECHNOLOGY AREAS: Ground/Sea Vehicles, Materials/Processes, Sensors

OBJECTIVE: Develop a sensor system capable of quantitatively assessing the degree of sensitization (DoS) in 5XXX aluminum alloys allowing in-situ application on ship structure.

DESCRIPTION: In order to assist maintenance decisions and guide predictions of structural integrity in service, a fieldable probe that can quantify the DoS of 5XXX alloys of interest to DON is required. The probe should be able to differentiate the DoS over the range of 5 to 50 mg/cm2 as determined by ASTM G67. It should be able to assess an area of material between 2 and 20 cm2 in a single measurement. It should be easy to be used on-board a ship or at a vehicle without the need to remove the structure of interest. The method should be applicable to a range of 5XXX alloys including 5083, 5456, 5059, 5383, 5454, and 5086. The ability to inspect welds and nearby regions would also be beneficial as well as a build-in calibration capabilities. The scientific basis for the measurement is not limited including methods based on ultrasonic, conductivity, optical, chemical, or electrochemical approaches.

The long-term benefit of such a probe would be its aid in developing an inspection approach that ensures aluminum ship structural integrity and health monitoring.

PHASE I: Conceptualize the capability to quantitatively measure DoS in a commercial 5XXX alloy, demonstrate on a single alloy in the 5XXX class under laboratory conditions and validate by comparison of results from ASTM G67 tests. The method must be applicable to development of a fieldable probe.

PHASE II: Develop and construct a prototype system capable of measurement of DoS on several 5XXX alloys on samples that show those expected to be found in service. The prototype should be applicable to 5XXX alloys in addition to those used in Phase I, i.e., robust enough to be applied to across different manufacturing lots of materials. A successful phase II effort will include delivery of a system which successfully maps out the DoS on a large (4�x4�) plate in both horizontal and vertical position in a lab setting.

PHASE III: Develop a robust portable inspection system that can quantitatively detect and assess degree of sensitization (DoS) in large area on Al ship hulls to provide improved condition-based maintenance decisions for ship structural integrity and health monitoring.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: These alloys are widely used in commercial marine structures and this method would be of use in the commercial ferry industry.

REFERENCES:
1. Craig, H. L., Jr., (1972), in Localized Corrosion � Cause of Metal Failure, ASTM STP 516, ASTM International, West Conshohocken, PA, pp. 17-37.

2. Davenport, A. J., Y. Yuan, et al. (2006). "Intergranular corrosion and stress corrosion cracking of sensitized AA5182." Aluminum Alloys 2006, Pts 1 and 2 519-521: 641-646.

3. Davis, D.A., Hays, R. A., (2002) NSWCCD-61-TR-2002/10, Naval Surface Warfare Center, West Bethesda, MD.

4. ASTM G 67-99 (2003) Annual Book of ASTM Standards, Vol. 03.02, pp. 273-275, ASTM International, West Conshohocken, PA.

KEYWORDS: corrosion, sensitization, corrosion measurement, aluminum alloys, Condition based maintenance