This SAE practice is intended for the sample preparation of test pieces for automotive wheels and wheel trim. The practice provides a consistent scribing method for use on test panels and or component parts with substrate chemical pretreatment and coating systems. Test specimens can then be subjected to various corrosion tests in order to evaluate performance without significant variations of the degree of exposure of the substrate. The scribing is used to create a break in the coating/finishing as can occur in the field through gravel and other damaging conditions.