PROCESS FOR THE ZINC-CALCIUM PHOSPHATIZING OF METAL SURFACES AT A LOW TREATING TEMPERATURE

摘要

The invention relates to a process for phosphatizing metal surfaces with an acidic phosphatizing solution containing zinc ions, calcium ions, phosphate ions and accelerators and, optionally, other additives, characterized in that, after degreasing and without activation, the metal surfaces are brought into contact at 30 DEG to 65 DEG C. with solutions which contain Zn2+, Ca2+, PO43- and, as accelerators, nitrate and/or nitrite and/or chlorate ions and/or an organic nitro compound and/or H2O2 or an inorganic peroxide and which have a pH-value of from 2.2 to 3.8, a ratio of free acid to toal acid of from 1:10 to 1:60 and a ratio by weight of (Ca2++Zn2+) to PO43- of from 1:8 to 1:40, and to the use of this process for pretreating the metal surfaces for painting by electrodeposition, particularly by cathodic electrodeposition.