SEDL / STP / STP841-EB / STP29522S

Quantitative Evaluation of Blistering and Corrosion in Organic Coating Systems

McKnight, ME
Research Chemist and Materials Research Engineer, Center for Building Technology, National Bureau of Standards, Washington, DC

Martin, JW
Research Chemist and Materials Research Engineer, Center for Building Technology, National Bureau of Standards, Washington, DC

Pages: 8    Published: Jan 1984

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Abstract

A nondestructive laboratory procedure using infrared thermography for detecting air- and water-filled blisters and localized corrosion at the coating/metallic substrate interface is described. Deteriorated areas are observed in real time as varying gray levels on the cathode ray tube of an infrared thermographic camera or after digitization of the signal on a TV monitor. Digitization of the analog signal permits (1) image enhancement through signal averaging techniques, (2) association of gray levels with degraded areas, (3) quantitative analysis of the panel for amount, location, and type of degradation, (4) computerized storage of the digitized signal for dynamic analysis of the degraded coating, and (5) graphic display of thermographic images. In addition to providing a non-destructive test for assessing degradation at the coating/substrate interface, these analyses will contribute to further understanding of corrosion mechanisms and the kinetics of degradation. This knowledge will be useful in developing improved accelerated tests for predicting coating durability.