Understanding Scribe Profile and Tool Type Effects on Visual Corrosion Assessments
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Visual analysis is the most common evaluation of accelerated corrosion performance after exposure using a scribed protective coating on a metal substrate. Although the scribed-coating visual inspection is standardized, the specificity of initial conditions relative to the final performance has never been unified between laboratories, scribing tools, nor by published testing standards. To validate the initial state of the coating performance based on the selected tool, salt spray corrosion tests ASTM B117 and GM14872 were performed on 60 epoxy-amine primer coated UNS 10080/10100 steel test panels with nine different scribes (3 test panels each with 3 non-scribed control panels). The width of the initial scribe greatly impacted the visual corrosion assessment of the test results during ASTM B117, while the initial scribe width had little impact during GM14872. These results suggest that correlating the initial scribe with the final corrosion evaluation of the coating defect resulted in a better inter-comparable evaluation of coatings subjected to visual analysis by accelerated corrosion or electrolyte corrosion.
KeywordsCorrosion Scribe Accelerated corrosion Epoxy primer Corrosion rate
The authors gratefully acknowledge the financial support of The United States Air Force (FA7000-13-2-0022 and FA7000-14-2-0011) through funding by the Department of Defense and collaborative efforts for Corrosion Prevention and Understanding via the Technical Corrosion Collaboration working group comprised of The University of Virginia, The University of Hawaii, The Ohio State University, the Air Force Academy, The University of Akron, The University of Southern Mississippi, the Air Force Institute of Technology, the Naval Postgraduate School, and the US Naval Academy.
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