Severe abrasion which smears the surface of the pipe, producing shallow surface laps. SpallingSevere abrasion which smears the surface of the pipe, producing shallow surface laps. Spalling is caused by mechanical damage and might be associated with denti… is caused by mechanical damagePhysical harm or degradation that occurs in a pipeline due to external forces, human activities, construction activities, or other mechanical actions. It can re… and might be associated with denting.