U.S. Department of Defence Armed with Science Update

A team of materials science researchers at The University of Virginia (UVA) has identified a magnesium-rich primer used as part of a normal paint system as a promising candidate to replace chromate-based paint systems that protect aluminum alloys.

"Several long-term studies, and some conducted in severe, natural environments, have demonstrated the primer’s excellent corrosion resistance," said John Scully, professor of Materials Science and Engineering at UVA, who leads a team of graduate-level researchers investigating the primer’s effectiveness. The team’s research has benefitted from funding provided by the DoD Corrosion Policy and Oversight Office under the aegis of the Technical Corrosion Collaboration (TCC).

An Air Force C-130 Hercules assigned to the 36th Airlift Squadron is ready to perform a low-cast, low-altitude airdrop at Yokota Air Base, Japan, in January, 2016. The C-130 and other aircraft models have undergone ground and in-flight exposure testing since 2007 as the DoD evaluated the effectiveness of a magnesium-rich primer. Photo by Osakabe Yasuo, U.S. Air Force.

An Air Force C-130 Hercules assigned to the 36th Airlift Squadron is ready to perform a low-cast, low-altitude airdrop at Yokota Air Base, Japan, in January, 2016. The C-130 and other aircraft models have undergone ground and in-flight exposure testing since 2007 as the DoD evaluated the effectiveness of a magnesium-rich primer. Photo by Osakabe Yasuo, U.S. Air Force.

"In spite of the promise that the magnesium-rich primer has shown over the past several years, the U.S. military has been slow to adopt a magnesium-rich primer for use on aircraft in the DoD fleet," said Bill Abbott, a former program manager at Battelle and an independent consultant for the DoD Corrosion Office. "We believe this is largely due to questions surrounding the exact reasons that magnesium provides protection, the effects of the chemical conversion of magnesium as it is ‘used up’ in service, how long the protection may last in service, and the performance of a magnesium-rich primer with various pretreatments and topcoats."

"All of the studies conducted by UVA and Battelle appear to present a consistent result, showing that the elemental magnesium present in the starting primer is in fact converted over time to magnesium hydroxide [Mg(OH)2] or magnesium carbonate (MgCO3)," said Scully. "Moreover, the results also explain the findings from independent natural environment studies, which suggest that the magnesium-rich primer system, which includes a pretreatment, primer, and topcoat, continues to provide excellent long-term corrosion protection, even after the magnesium is believed to be effectively "used up" or converted to a form that might not continue to provide sacrificial-anode-based corrosion protection."

Recently, Santucci examined how the coating system performed on samples painted with different topcoats during a two-and-a-half-year exposure period. He concluded that the primer’s performance when used in conjunction with diverse topcoats is similar. UVA researchers also confirm independent natural environment studies that demonstrate that the magnesium-rich primer provides excellent corrosion protectio
Source :WAM