| 摘要 |
A process is disclosed for preparing an aqueous zinc phosphatizing solution for producing phosphate coatings on metallic surfaces of iron, steel, zinc, zinc alloys, aluminum or aluminum alloys, which comprises:(1) 0.3 to 5 g Zn2+/1;(2) 0.1 to 3 g nitroguanidine/1 as an accelerator;(3) phosphate where the acid value is 0.03 to 0.3 indicating the ratio of free acid, calculated as free P2O5 to the total P2O5, and the weight ratio of Zn to P2O5 is 1:5 to 1:30; and(4) balance water, where the solution produces finely crystallite phosphate coatings in which the crystallites have a maximum edge length <15 mum, which comprises the steps of:(a) preparing a concentrate comprising the Zn2+ and the phosphate in water;(b) supplying additional water to the concentrate so that the Zn2+ concentration in the phosphatizing solution is 0.3 to 5 g/1;(c) preparing a stabilized suspension consisting essentially of 100 to 300 g of nitroguanidine/1, 10 to 30 g of sheet silicate/1 as stabilizer and the balance water by suspending the sheet silicate in deionized water and stirring the nitroguanidine into the suspension; and(d) introducing the stabilized suspension into the phosphatizing solution so that the nitroguanidine concentration in the phosphatizing solution is 0.1 to 3 g nitroguanidine/liter.
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