Southwest Research Institute (SwRI) News
Printer Friendly VersionSwRI®-developed sensor detects early paint and coating degradation
San Antonio -- September 23, 2003 -- Corrosion engineers at Southwest Research Institute® have developed an embedded sensor system that can detect paint and non-metallic coating degradation on metal structures before it can be noticed by the human eye.
Corrosion under coatings and in hidden areas is a major problem, especially for bridge deck structures, automotive components, electronic packages and aircraft structures. At present, maintenance cycles for these structures are often based on experience and visual appearance. Continuous monitoring, early detection and remote data gathering could increase safety and enable more cost-effective maintenance.
The new, patent-pending embedded sensor system developed at SwRI consists of an array of pins that penetrate the substrate from underneath the substrate, electronics to conduct the measurement, and radio frequency telemetry and data transmission components. Fabrication using silicon microspheres enables the sensor probes to be applied with the coating.
The sensor measures the electrical impedance between two systems, in this case a metal and its surface coating, or paint. The sensor can be assembled using commercial off-the-shelf components, and its placement does not adversely affect coating performance. Depending on the application, the system can be custom configured to a variety of hardware packages from hand-held computers to large, remote workstations.
"Previous research in this area was restricted to systems that required physical contact with the top of the coating, and in many cases resulted in coating degradation or damage at the test site," said Dr. Sean Brossia, a senior research engineer in SwRI's Mechanical and Materials Engineering Division. "The SwRI-developed system overcomes this by embedding the sensor probes either underneath or within the coating. Testing has demonstrated that such configurations do not lead to coating degradation even under highly aggressive conditions."
In laboratory tests, three-coat polyurethane, one-coat polyurethane and one-coat enamel coatings were evaluated on carbon steel and aluminum alloy substrates. In each instance, the sensor was able to detect laboratory-induced degradation successfully. Besides degradation, the sensor can also detect defects in the form of surface contamination and coating damage.
The sensor can be placed in areas not easily inspected for coating integrity and can detect the onset of coating degradation prior to significant substrate corrosion. Additionally, the sensor can be used to monitor the corrosivity of rinse water and to test the effectiveness of corrosion inhibitors.
Currently the sensor is being used to monitor coating degradation in aircraft, but the technology could be easily applied to automobiles, trucks and military vehicles as well as large structures such as suspension bridges.
For more information about the coating degradation sensor and SwRI corrosion technology, contact James Dante at (210) 522-6238 or jdante@swri.org.
For more information, contact Deborah Deffenbaugh, Communications Department, (210) 522-2046, Fax (210) 522-3547, PO Drawer 28510, San Antonio, TX 78228-0510.
