| 摘要 |
PROBLEM TO BE SOLVED: To produce a surface treated steel plate having safety and excellent corrosion resistance by treating a zinc plated steel plate with a chromium free aqueous treating solution. SOLUTION: A chemical conversion coating film is formed in 0.005-2.0μm thickness on a galvanized surface by treating a zinc plated steel plate with an acidic aq. solution of pH 1.0-4.0 followed by heat-treating. The acidic aq. solution contains a silicate and/or silica fine particles of 0.01-3.0 mol/L in total amount expressed in terms of SiO2 , 0.001-2.0 mol/L of Al ion, 0.001-2.0 mol/L of Mg ion, and moreover contains 0.001-6.0 mol/L of nitric acid ion and 0.001-6.0 mol/L of chlorine ion as anions, and further preferably contains one or more than two kinds selected from metal ions of Ca, Sr, Ba, Hf, Zr, V, Ti, Ce, La, Ni, Co, Fe, Mn and a water-soluble cation contg. one of these metals.
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