By Debbie Gregory.

It scours the bottom of Navy ships, invades the crevices of Air Force jets and costs the Pentagon more money annually than many of its most expensive weapons systems—up to $21 billion per year, according to a Defense Department-commissioned audit.

Corrosion happens to anything exposed to weather, including the metals that make up modern weapons systems like fighter jets, ships, ballistic missiles and nuclear weapons.

In 2002, the department established the Office of Corrosion Policy and Oversight to ensure big-dollar weapons systems weren’t taken offline by oxidation and to help branches determine how much money ought to be spent on rust prevention.

Technically, the problem is bigger than just rust. Rust is only the most commonly known type of corrosion, and occurs when iron reacts with water or moist air. The broader category includes any type of metal broken down or disintegrated by a chemical reaction. Data being reported by the military branches has been inconsistent and the office has yet to issue guidance on how funding levels should be categorized, according to a related audit released Thursday by the Government Accountability Office (GAO).

“The Army data GAO received did not reconcile with data presented in the Corrosion Office annual reports to Congress for five of eight fiscal years,” auditors wrote. “The Navy data did not reconcile for two of eight fiscal years, and there was no supporting documentation identifying how these figures were calculated. Air Force officials did not provide any figures or supporting documentation for four fiscal years, stating that these figures were not available.”

Army officials told GAO they’re not able to accurately report how much is spent preventing or combating corrosion because many of those duties are performed by personnel who do many other things, as well.

“The corrosion-related costs of conducting the corrosion executive role are not separated from this other function,” they told GAO.

The GAO has made the following recommendations to the Defense Department:

• Issue guidance for identifying and reviewing funding levels for performing corrosion executive duties.
• Ensure that the Corrosion Office develops a process to maintain documentation of its reviews of corrosion planning.
• Ensure that corrosion executives establish guidance on reviewing the adequacy of corrosion planning.

While the military is looking into more coating options – from aluminum- to polyurethane-based waterproofing – there are some alternatives. Cathodic protection is an electro-chemical process that prevents corrosion entirely, and super-finishing is a surface treatment process that prevents damage from friction.