Met-L-Check procedure

The Met-L-Chek process (also capillary, suction, penetration processes ) is a non-destructive material test to find the smallest cracks on the workpiece surface. Here, a mostly red dye is first applied to the cleaned workpiece and the surface is thoroughly freed from it again after an exposure time of approx. 10 minutes. The dye that has penetrated into existing hairline cracks due to the capillary action remains in the cracks. Now the surface is sprayed with a white dye, which pulls out the red dye present in potential hairline cracks. This process makes even the smallest surface damage visible that cannot be seen with a magnifying glass. Often the red dye is also fluorescent in order to make the damage even more visible in combination with ultraviolet light.

This procedure corresponds to the further development of the oil boiling test , in which the workpiece is immersed in hot oil for several minutes and the oil penetrates cracks. Then the workpiece is cleaned and whipped chalk is applied. As a result of the cooling, the oil that has penetrated is now pressed out of the cracks and a brown color is evident at the imperfections.