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make sure you have someone that has a ceramic bead and not just aluminum oxide media. the coarse highly abrasive aluminum oxide or similar will leave a coarse finish that has cut in to the metal. this makes for a more corrosion resistant and scratch prone finish. if you go with a ceramic bead media that peens the surface and adds the nice matte finish without being prone to superficial scratches and will not leave a coarse surface that houses moisture and helps corrosion.