| 摘要 |
A black coating method for a cellular phone LCD bracket die-casting molded from an aluminum-magnesium alloy is provided to substantially lower the defective proportion of a product by preventing distortion after demolding and removing burrs during a sprue cutting, punching and post-treatment easily and neatly, and prevent scattered reflection of an LCD screen by performing a black coating process on a thin bracket. A black coating method for a cellular phone LCD bracket die-casting molded from an aluminum-magnesium alloy comprises: a step of injecting an alloy melt comprising 9.740 wt.% of Mg, 0.430 wt.% of Fe, 0.430 wt.% of Mn, 0.180 wt.% of Si, 0.080 wt.% of Cu, 0.030 wt.% of Zn, 0.010 wt.% of Cr, 0.009 wt.% of Sn, 0.009 wt.% of Ti, 0.008 wt.% of Ni, 0.006 wt.% of Pb, and the balance of Al and other inevitable impurities into a mold cavity to die-casting mold a bracket including an LCD receiving part and a frame joining part of the edge; a nickel coating step(NP) of sequentially passing the molded bracket through a chemical nickel coating process(NP1), a copper sulfate coating process(NP2), a semi-gloss nickel coating process(NP3), and a gloss nickel coating process(NP4); a chromium coating step(CP) of sequentially passing the nickel coated bracket through a microporous nickel coating process(CP1), a chromium activating process(CP2), and a chromium coating process(CP3); and a step of forming fine irregularities on a surface of the bracket passing through the chromium coating step using a strong alkaline solution, and forming a block coating on the bracket by spraying a paint comprising a black pigment onto an inner circumferential surface of an opening that functions as a display window for the LCD in order to prevent scattered reflection of an LCD.
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