U.S. Department of Defence Armed with Science Update

WASHINGTON, 22nd April, 2016 (WAM)--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 protection with a wide range of pretreatments, and also evinces little adverse effect on corrosion protection after two and a half years of exposure, even when the primer is used in conjunction with different types of military-grade topcoats.

During a programme to test the performance of a magnesium-rich primer, the Navy P-3C Orion was subjected to severe outdoor exposure testing on the ground around Daytona Beach, Florida, from 2007 to the present. The P-3 was also subjected to flight exposure testing from 2009 to 2014. Photo by Victor Pitts, U.S. Navy.

During a program to test the performance of a magnesium-rich primer, the Navy P-3C Orion was subjected to severe outdoor exposure testing on the ground around Daytona Beach, Florida, from 2007 to the present. The P-3 was also subjected to flight exposure testing from 2009 to 2014. Photo by Victor Pitts, U.S. Navy.

"These conclusions will be of considerable importance to policy considerations that may impact the practical application of new chromate-free paint systems," said Rich Hays, deputy director of the DoD Corrosion Office.

"These results should diminish concerns about whether systems of this type, based on an initial cathodic protection by magnesium, should lose their effectiveness over time," Scully said. "This work is important in that it provides a technical basis for concluding that the corrosion protection will not be lost. A simple explanation is that the magnesium does provide cathodic protection for some period of time. In addition, over the long term, a barrier film of magnesium hydroxide will rapidly form at defects such as scratches and continue to provide excellent corrosion protection."

"The results from UVA’s research are consistent with other natural environment exposure results that have shown no evidence of corrosion degradation on any full paint stack-ups on aluminum alloys using the magnesium-rich primer," Scully explained. This conclusion has been extended to such systems that have been exposed in a severe natural environment for years, and then scribed, followed by extended exposure.

"At the DoD Corrosion Office, we believe the positive results of these UVA studies represent the successful way in which the TCC program was designed to function," noted Hays. "Under the auspices of the TCC, we fund and support research that addresses problems of immediate concern to the Department of Defense, which may lead to a rapid process of implementation on DoD’s fleet of aircraft, ships, ground vehicles, and infrastructure."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 protection with a wide range of pretreatments, and also evinces little adverse effect on corrosion protection after two and a half years of exposure, even when the primer is used in conjunction with different types of military-grade topcoats.

During a program to test the performance of a magnesium-rich primer, the Navy P-3C Orion was subjected to severe outdoor exposure testing on the ground around Daytona Beach, Florida, from 2007 to the present. The P-3 was also subjected to flight exposure testing from 2009 to 2014. Photo by Victor Pitts, U.S. Navy.

During a program to test the performance of a magnesium-rich primer, the Navy P-3C Orion was subjected to severe outdoor exposure testing on the ground around Daytona Beach, Florida, from 2007 to the present. The P-3 was also subjected to flight exposure testing from 2009 to 2014. Photo by Victor Pitts, U.S. Navy.

"These conclusions will be of considerable importance to policy considerations that may impact the practical application of new chromate-free paint systems," said Rich Hays, deputy director of the DoD Corrosion Office.

"These results should diminish concerns about whether systems of this type, based on an initial cathodic protection by magnesium, should lose their effectiveness over time," Scully said. "This work is important in that it provides a technical basis for concluding that the corrosion protection will not be lost. A simple explanation is that the magnesium does provide cathodic protection for some period of time. In addition, over the long term, a barrier film of magnesium hydroxide will rapidly form at defects such as scratches and continue to provide excellent corrosion protection."

"The results from UVA’s research are consistent with other natural environment exposure results that have shown no evidence of corrosion degradation on any full paint stack-ups on aluminum alloys using the magnesium-rich primer," Scully explained. This conclusion has been extended to such systems that have been exposed in a severe natural environment for years, and then scribed, followed by extended exposure.

"At the DoD Corrosion Office, we believe the positive results of these UVA studies represent the successful way in which the TCC programme was designed to function," noted Hays. "Under the auspices of the TCC, we fund and support research that addresses problems of immediate concern to the Department of Defense, which may lead to a rapid process of implementation on DoD’s fleet of aircraft, ships, ground vehicles, and infrastructure."


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