Characterisation of decohesion/cracking of paint and coatings by electronic speckle pattern interferometry

Paints and coatings are a popular mitigation measure for corrosion of various industrial components in service. Accurate early detection of decohesion of paints/coatings is invaluable for the proper maintenance of coated components. Recent advances in electronic speckle pattern interferometry (ESPI) provide the capability of sensitive and precise detection of out-of-plane displacements. This paper presents recent laboratory results investigating the application of ESPI as a non-contact and non-destructive technique for the detection of decohesion of artificially created thin films over a steel substrate. Based on the success of the ESPI in detecting the decohesion of artificial paints, the technique was successfully extended to typical paints and coatings used in naval applications. This paper also establishes the need to use an external excitation source of a specific frequency range for the characterisation of decohesion in a given paint-substrate system.