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In the present work, the temperature versus thermal deformation (strain) with respect to time, of
different coating films were studied by a non-destructive technique (NDT) known as shearography. An
organic coating, i.e., epoxy, a white enamel, and a yellow Acrylic Lacquer on a metallic alloy, i.e.,
carbon steels, were investigated at a temperature range simulating the severe weather temperatures in Kuwait
especially between the daylight and the night time temperatures, 20-60 °C. The investigation focused on
determining the in-plane displacement of the coatings, which amounts to the thermal deformation (strain) with
respect to the applied temperature range. Furthermore, the investigation focused on determining the thermal
expansion coefficients of coatings, the slope of the plot of the thermal deformation (strain) versus the applied
temperature range. In other words, one could determine, from the decreasing value of the thermal
expansion coefficients of coatings, a critical (steady state) value of the thermal expansion coefficients of
coatings, in which the integrity of the coatings can be assessed with respect to time. In fact, determination of
critical (steady state) value of the thermal expansion coefficients of coatings could be accomplished
independent of parameters, i.e., UV exposure, Humidity, exposure to chemical species, and so on, normally
are considered in conventional methods of the assessment of the integrity of coatings. In other words, with
the technique of shearography, one would need only to determine the critical (steady state) value of the
thermal expansion coefficients of coatings, regardless of the history of the coating, in order to assess the
integrity of coatings. Furthermore, results of shearography indicate that the technique is very useful NDT
method not only for determining the critical value of the thermal expansion coefficients of different coatings,
but also the technique can be used as a 2D- microscope for monitoring the deformation of the coatings in realtime
at a submicroscopic scale.
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