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

摘要

The invention provides a zirconium ion containing surface pretreatment fluid for the metal to be coated by cationic electrodeposition which makes it possible to develop satisfactory throwing power in the electrodeposition and is excellent in corrosion inhibition performance. The invention relates to a surface pretreatment fluid for the metal to be coated by cationic electrodeposition which contains zirconium ions and tin ions and has a pH of 1.5 to 6.5, wherein the zirconium ion concentration is 10 to 10000ppm and the content ratio by mass of tin ion to zirconium ion is 0.005 to 1. The fluid may further contain a polyamine, copper ion, fluoride ion, or a chelate compound.