Most self tapping screw exterior coating system using galvanized or zinc phosphate coating. Because of its high cost and toxicity of cadmium plating so rarely used if appearance is important, then, to pick and nickel or chrome. Surface disposal will attack two questions: first, the appearance of disposal will not only increase the scale (for example, cavity decreases) and appearance of disposal will not affect the torque, screw the degree of strength between contact, so scoring experiments shall be galvanized, or phosphates, cadmium plated-disposal do not rule. Test for attack when the hole diameter, the use of screws must be the same appearance of the disposition of the screw. Second, high hardness, small self tapping screws using loss resulting from hydrogen embrittlement. Self tapping screws in order to score iron shall not carburizing disposed. Will attack after the carburizing disposed of high hardness and high carbon content, as well doing plating or acid disposal will attack the hydrogen embrittlement. Specification the approach advocated the Elimination of hydrogen embrittlement: a). plating or acid disposal purposes within 1 hour after baking. b). 375 ~ 425 oF temperature (190 ~ 220 oC). time for at least 4 hours.