Coating thickness in welded joints and its effect on detectability by magnetic particle testing

Magnetic particle nondestructive testing is widely used to evaluate defects in welded structures and components and to ensure their reliability and functionality. As they are often subjected to surface coating processes to extend their service life, there is uncertainty in the detection of these defects, so it was proposed to determine the effect of coating thickness size on the ability of magnetic particle testing to reveal defects in welded joints. Tests were performed on welded specimens containing surface defects and coated at three thickness levels. The estimation of the detection capability of the tests was performed by the POD Hit/miss statistical method using the mh1823POD program, obtaining the probability of detection curves for each thickness level. The results showed that as the coating thickness increases, the detection rate and capacity decrease; the magnetic particle inspection presents a better performance in samples with an average thickness of 73 μm, detecting defects greater than or equal to 14.15 with a high probability.