ABSTRACT Corrosion resistance of zinc coatings containing various metal ions was evaluated by a salt spray test. At first, we studied the effect of impregnated metal ions such as Al3+ Mg2+ and Cr3+ into pores in the zinc coatings prepared by using a porous zinc electroplating bath including No3-. As a result, the corrosion resistance of zinc coatings increased compared with that of non impregnation. Then, we investigated the same effect in zinc coatings using an acid composite zinc electroplating bath containing divers metal ions. In case of the composite electroplating, Mg was not deposited in zinc coatings, but Al and Cr were co-deposited as metal oxides or hydroxides. By providing composite coatings containing 0.5 to 1.5 wt% Al or 0.3 to 20 wt% Cr on a steel sheet , the corrosion resistance increased 5 to 10 times as high as ordinary electrogalvanized steel sheet., The adhesion property and workability were also improved. |
