ESPI nondestructive testing for coating interface failure

A detection platform of coating failure processes was designed and constructed on the basis of laser electronic speckle pattern interferometry (ESPI). In situ, real-time and dynamic speckle interference fringes were observed and optimized without destroying the coating. An image of coating failure information was acquired by subtracting the zero moment stripe from the in situ and real-time stripes observed and binarizing the results. An experiment of the epoxy color paint/carbon steel system demonstrated the validity of ESPI. According to the ESPI image change, the immersion process of the epoxy color paint coating was divided into three stages: no spots in the initial stage, several blurry spots in the second stage and many clear spots in the last stage. As a result, we successfully realize the in situ, real-time and dynamic nondestructive testing of the coating interface failure and the microcosmic progress of under-film metal corrosion.