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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 nondestructive technique (NDT) known as shearography. An organic
coating, i.e., ACE Premium Enamel, on a metallic alloy, i.e., a carbon steel, was 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 coating,
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 real-time at a submicroscopic scale.
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