| 摘要 |
Disclosed is a method for zinc phosphating a molded metal article wherein a treating bath composition comprises from 1.5 to 5.0 g/l of zinc ion, from 0.1 to 3.0 g/l of manganese ion, from 5 to 40 g/l of phosphate ion, from 0.05 to 3.0 g/l of a fluorine compound as HF and hydoxylamine as a chemical conversion accelerator. A concentration of hydroxylamine is maintained to satisfy the following relationship: 0.5</=[hydroxylamine](g/l)-2.0x[Fe2+](g/l)</=3.0 The treating bath is agitated by a vibratory agitating means provided in the treating vessel so that a mean acceleration a of a treating solution present within a bath region in which the molded metal article is immersed to be treated under fluid agitation is at least 8 cm/sec2. The mean acceleration is calculated from the following equation: <IMAGE> wherein values of X, Y and Z, each in unit of cm/sec2, indicate average acceleration values of treating solution in three respective X, Y and Z axial directions which are perpendicular to each other. The velocity changes of the treating solution in a flow state in respective X, Y and Z directions are synchronously measured at measuring locations for 60 seconds to be averaged to obtain the respective average acceleration values in X, Y and Z directions.
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