Visualizing the impact of mechanical strain and the environment on pipeline coatings from a three dimensional perspective

•X-ray computed tomography (CT) has been used to characterize heterogeneities in coatings.•CT results appear to provide a physical basis for the historical D and I coating concepts.•CT results are corroborated by three dimensional FEA modelling.•The formation of a tortuous void network in a heterogeneous coating has been described.•Coating degradation processes are illustrated based on CT results and FEA modelling.