| 摘要 |
The phenomenon of "mapping" (surface defects) after electrophoretic painting ove r phosphate conversion coatings passivated with hexavalent chromium containing passivating compositions can be avoided or reduce d by keeping the surface being treated constantly wet from the time it is conversion coated until it is electrophoretically painted, b y preceding the passivating step by treatment with an aqueous liquid treatment composition comprising at least one of the following components ; (A) a water soluble and/or water dispersible polymer with a weight average molecular weight of at least 500; (B) fluorometallic acids and anions thereof, the molecules of which consist of (i) at least one atom of boron, silicon, zirconium, iron, aluminum, or titanium, (ii ) at least four fluorine atoms, and, optionally, (iii) one or more atoms of oxygen, hydrogen, or both; (C) zirconium salts of ethylenediamine acid; and (D) alkali metal and ammonium zirconyl carboxylates and carbonates; or by replacing the chromium containing pa ssivating composition with an aqueous liquid treatment composition of the same type as described above.
|
