A Novel Linear Polarization Resistance Corrosion Sensing Methodology for Aircraft Structure

Douglas Brown, Richard Connolly, Bernard Laskowski, Margaret Garvan, Honglei Li, Vinod Agarwala, and George Vachtsevanos
Submission Type: 
Full Paper
Supporting Agencies (optional): 
Air Force Research Laboratory
phmc_14_033.pdf1.48 MBSeptember 16, 2014 - 3:14pm

A direct method of measuring corrosion on a structure using a micro-linear polarization resistance (uLPR) sensor is presented. The new three-electrode uLPR sensor design presented in this paper improves on existing LPR sensor technology by using the structure as part of the sensor system, allowing the sensor electrodes to be made from a corrosion resistant or inert metal. This is in contrast to a two-electrode uLPR sensor where the electrodes are made from the same material as the structure. A controlled experiment, conducted using an ASTM B117 salt fog, demonstrated the three-electrode uLPR sensors have a longer lifetime and better performance when compared to the two-electrode uLPR sensors. Following this evaluation, a controlled experiment using the ASTM G85 Annex 5 standard was performed to evaluate the accuracy and precision of the three-electrode uLPR sensor when placed between lap joint specimens made from AA7075-T6. The corrosion computed from the uLPR sensors agreed with the coupon mass loss to within a 95% confidence interval. Following the experiment, the surface morphology of each lap joint was determined using laser microscopy and stylus-based profilometry to obtain local and global surface images of the test panels. Image processing, feature extraction, and selection tools were then employed to identify the corrosion mechanism (e.g. pitting, intergranular). Features extracted from images were correlated with exposure time and LPR sensor measurements.

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Submission Keywords: 
structural health management
fault diagnostics
failure analysis
Submission Topic Areas: 
Structural health monitoring
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