The surface protection processes are performed for metals in order to improve paint adhesion and dye yield, increase corrosion strength, and eliminate the necessity of re-processing. The desired quality to be received in the parts processed in the surface protection processes which constitutes multiple sub-processes can be obtained only if the sub-processes are conducted effectively. In this study, the criteria being effective on surface protection processes have been identified, and an approach based on the Analytic Hierarchy Process (AHP) and the process capability (C-p) values have been developed in order to identify the significance level of these criteria on the surface quality. The approach developed has been applied to the immersion phosphating process of a large-scale company. First of all, the significant levels of sub-processes were identified through the AHP method based on the quality parameters followed by the company. Then the C-p values were calculated based on the measurement criteria in order to understand the competence of each sub-process. Important subprocesses affecting the final quality of the immersion phosphating process have been identified by means of the PPN (Process Priority Number) index developed by using the AHP results and C-p values.