Degradation of organic coatings in a corrosive environment: a study by scanning Kelvin probe and scanning acoustic microscope

Degradation of pigmented epoxy coatings on a steel substrate during exposure to aerated 3% NaCl solution has been investigated using the scanning Kelvin probe (SKP) and scanning acoustic microscopy (SAM). A method for processing SKP potential maps has been used to visualize the distribution of anodi...

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Bibliographic Details
Published in:Progress in organic coatings 2005-04, Vol.52 (4), p.280-287
Main Authors: Reddy, B., Sykes, J.M.
Format: Article
Language:English
Subjects:
Applied sciences
Coatings. Paints, varnishes and inks
Corrosion
Corrosion mechanisms
Exact sciences and technology
Film formation and curing, properties, testing
Metals. Metallurgy
Paints
Pigments
Polymer industry, paints, wood
Scanning acoustic microscopy
Scanning Kelvin probe
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Summary:Degradation of pigmented epoxy coatings on a steel substrate during exposure to aerated 3% NaCl solution has been investigated using the scanning Kelvin probe (SKP) and scanning acoustic microscopy (SAM). A method for processing SKP potential maps has been used to visualize the distribution of anodic and cathodic current. It was observed that rust deposited at the defects, or later beneath the coating, acted as a cathodic reactant, leading to development of new anodes beneath the coating. Exposure of rusty samples to moist air (rather than salt solution) during SKP mapping is shown to lead to more noble potentials at the defect that influence the electrochemistry of under-film processes.
ISSN:0300-9440
1873-331X
DOI:10.1016/j.porgcoat.2004.04.004