| 摘要 |
<p>The invention relates to a process for coating metallic surfaces with a phosphating coating by contacting metallic surfaces at a temperature not above 45 ¦C and at a pH value less than 3.5 with an aqueous acidic alkali metal phosphating solution or dispersion containing: At least one compound of at least one phosphorus containing acid and/or at least one of their derivatives like esters and salts in a total content of all kinds of acids and all their derivatives like esters and salts together of less than 20 g/L calculated on mole base as orthophosphate, whereby the content of such phosphorus containing compounds/ions is at least 50 % by weight in comparison to all such compounds/ions and at least one ion selected from the group consisting of at least one alkali metal ion and ammonium ion, whereby the phosphating coating has a coating composition with a phosphorus content of not more than 8 atomic% as measured by Secondary Neutral Mass Spectroscopy (SNMS) and whereby the phosphating coating has a coating weight in the range from 0.01 to 0.5 g/m2.</p> |
