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Army Uses Smart Technology to Fight Corrosion at Fort Bragg

By Gretchen Jacobson

The inlet pipe at Fort Bragg's Central Vehicle Wash Facility has severe coating degradation, which is being mitigated with a combination of fluorescent and self-healing coatings. Photo courtesy of Army Corps of Engineers.

North Carolina's Fort Bragg, one of the largest and busiest military complexes in the world, houses and trains nearly 10% of the Army's active component forces. Widely known as the "Home of the Airborne and Special Operations Forces," the 88-year-old fort supports the most intensive and varied training program in the continental United States. Millions of personnel days are dedicated to training each year using aircraft, tactical vehicles, and equipment to prepare and ready military units for deployment.

The vehicles used for maneuvers in the field require diligent maintenance to protect them from such hostile elements as heat, humidity, mud, sand, and swamp water. Following the training exercises, each vehicle must be cleaned and decontaminated to prevent corrosion and ensure long-term dependability. The undersides of the vehicles, often caked in mud, are particularly susceptible to corrosion.

A crucial component of Fort Bragg's vehicle maintenance system is its Central Vehicle Wash Facility (CVWF). Most army installations have one or more CVWFs to provide rapid and economical cleaning of tactical vehicles. Following training exercises, the vehicles go through the CVWF pools, and water canons remove the mud and other debris. The mud is then flushed out of the CVWF systems into a grit-settling chamber. A 200-feet-long, 2-feet-diameter carbon steel, inlet pipe carries grit, oil, and other contaminants to the chamber.

Fort Bragg personnel have identified severe corrosion problems at the CVWF, primarily on the inlet pipe, which is experiencing pitting caused by its proximity to the washbasin water, exposure to the humid atmosphere, and a failing coating system. If the problem is not rectified, the CVWF must be shut down for frequent repairs, rendering it unusable for substantial periods of time. This in turn adversely affects the ability to promptly clean and maintain the vehicles, leading to concentration cell corrosion on their undersides.

"The average worker with 20/20 vision can usually locate a defect 0.5 mm in size," said Stephenson. "UV fluorescence allows the same worker to locate defects 0.1 mm in size or smaller, even in low-light conditions."

To rectify this problem, the Army Corps of Engineers began exploring the use of smart fluorescent and self-healing coatings in 2005 to protect CVWF components in the severe environment. The project—managed by the Engineer Research and Development Center's Construction Engineering Research Laboratory (CERL) and funded by the DoD Corrosion Policy and Oversight Office—demonstrates and validates these advanced coatings technologies in the field.

"The advanced technologies proposed for demonstration and validation have been researched in the laboratory but require application and study in operational environments," said Associate Project Lead L. David Stephenson at CERL. "We are confident that our corrosion control efforts will be significantly enhanced by using this coatings system at the Fort Bragg facility and elsewhere in the Tri-Services."

Commercially available fluorescent coatings contain additives that fluoresce under ultraviolet (UV) light inspection and reveal areas where coatings have developed holidays, coverage is incomplete, and where corrosion has initiated under the coating. With the fluorescent additives in the primer, areas of brighter-than-normal luminosity tend to indicate higher-than-expected dry film thickness (DFT); duller-than-normal luminosity indicates lower-than-expected DFT. After a topcoat is applied, the fluorescence should disappear; areas where the fluorescence is still present are indicative of a lower-than-normal topcoat thickness. In addition, organic dust and grit show up as speckled bright spots under the UV light, and areas of black spots are indicative of undercoating.

The CERL researchers anticipate that fluorescent coating inspection will ensure longer periods of maintenance-free service and reduce paint usage, which will in turn reduce volatile organic compound emissions at the site. Workers can take corrective action when necessary and recoat damaged areas before corrosion becomes a serious problem.

"Like our coatings projects at Fort Campbell, we expect the life of the CVWF components at Fort Bragg to be extended by 30 years."

In a technology breakthrough, the researchers also are incorporating self-healing coatings into the smart fluorescent coating system. Self-healing coatings are made by incorporating microcapsules that contain film-formers and corrosion inhibitors into commercially available paint primers at the time of coating application. When a self-healing coating is scratched, the microcapsules break and release their inhibitors and film formers, which protect the underlying steel and repair coating damage. The coating will be used to protect critical areas on the inlet pipe, such as welded joints.

Stephenson and his team have been using self-healing coatings to protect hangars, towers, and tanks at Fort Campbell. (See Project News, Spring 2006 CorrDefense.) Ongoing evaluations indicate that implementing surface-tolerant and self-healing coatings will extend the life of the Fort Campbell structures by 30 years.

"Like our coatings projects at Fort Campbell, we expect the life of the CVWF components at Fort Bragg to be extended by 30 years," said Stephenson. "Once our testing has been completed and the new coating systems are implemented, we believe the outcome will be to sustain the CVWF at its optimum operating condition, as well as reduced maintenance and increased safety both for the CVWF facility and the tactical vehicles it cleans."