Efficient operating of drilling system depends on the technical condition of the equipment. Therefore, nondestructive testing of the breaking pads is an important task. Image processing approach is proposed to evaluate the degradation degree of the brake pad by the analysis of its friction surface. The image preprocessing step includes elimination of uneven illumination and geometrical transformation. The parameterized Retinex method is applied with the purpose to remove non-uniform illumination. The mapping of brake pad surface to the rectangular image of predefined size is performed to avoid the influence of surface curvature and angle of image acquisition. The scale-space theory is used for crack detection. Integral characteristics are calculated based on segmented and skeletonized cracks. They are proposed to estimate the degree of brake pad surface degradation. Experimental results of proposed method application are demonstrated on operated brake pads surfaces.