COATED STEEL PANEL EXCELLENT IN PROCESSABILITY AND PROCESSED PART CORROSION RESISTANCE AND METHOD FOR MANUFACTURING THE SAME

摘要

PROBLEM TO BE SOLVED: To obtain a coated steel panel having excellent processability extremely reducing the generation of a crack in a coating film and also excellent in processed part corrosion resistance. SOLUTION: The coated steel panel has such a structure that a chemical forming treatment film is provided on the surface of the plating film on a steel panel and an undercoating film (a) and a topcoating film (b) are provided on the chemical forming treatment film. The undercoating film (a) is based on a modified polyester resin (C) and a hardening agent (D), and is obtained by reacting a polyester resin (A) and an epoxy resin (B). The k value represented by formula (1): k=[Wb×(Ma+2×Mb)]/[(Wa+Wb)×2×Mb] wherein, Wa is a solid weight ratio of (A) to [(A)+(B)], Wb is a solid weight ratio of (B) to [(A)+(B)], Ma is a number average mol.wt. of (A), and Mb is a number average mol.wt. of (B)] is 0.7-2.5, and a curing agent (P) and the topcoating film (b) is based on a polyester resin (E) and a hardening agent.