Honda Motor Co., Ltd.

Nippon Paint Surf Chemicals Co., Ltd.

Yuji Ohtake

Takayuki Ueno

Yuki Kasahara

Katsuyoshi Kaneko

Tatsumasa Hidaka

Osamu Izumi

Yu Koganezawa

Yuya Kotani

Koichiro Izumi

Provided is a method of performing pre-paint treatment of an automobile body including a high-tensile steel sheet, in which desirable corrosion resistance can be obtained after painting. A method of performing pre-paint treatment of an automobile body, the method including performing an alkaline degreasing step, a first water-washing step, a chemical conversion treatment step, a second water-washing step, and a cationic electrodeposition painting step, in this order, wherein the chemical conversion treatment step is performed using an chemical conversion treatment agent including zirconium (A), free fluorine ions (B), an allylamine-diallylamine copolymer (C), aluminum ions (D), nitrate ions (E) each at a predetermined concentration; the allylamine-diallylamine copolymer (C) forms an acid addition salt having an anionic counter ion, and the pKa of an acid thereof falls within the range of &#x2212;3.7 to 4.8; and the content percentage of diallylamine is 80 mol % or more and 98 mol % or less.

Method of performing pre-paint treatment of automobile body and automobile body

Growing community of inventors

Tokyo, Japan

Yuji Ohtake