SURFACE PRETREATMENT FLUID FOR THE METAL TO BE COATED BY CATIONIC ELECTRODEPOSITION

摘要

The invention provides a surface pretreatment fluid for the metal substra te to be coated by cationic electrodeposition which makes it possible to att ain satisfactory throwing power in the electrodeposition and which is excell ent in corrosion inhibition performance. A surface pretreatment fluid for th e metal to be coated by cationic electrodeposition which contains zirconium ions, copper ions and other metal ions and has a pH of 1.5 to 6.5, wherein t he above other metal ions are at least one kind of ions selected from the gr oup consisting of tin ion, indium ion, aluminum ion, niobium ion, tantalum i on, yttrium ion, and cerium ion, and the zirconium ion concentration is 10 t o 10000ppm with the concentration ratio of copper ion to zirconium ion and t hat of other metal ion to copper ion being 0.005 to 1 by mass and 0.1 to 100 0 by mass respectively.