| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a chromium-free surface treated steel sheet excellent in corrosion resistance in a flat plate or after processing, even if subjected to alkaline decreasing by a user or exposed in a corrosive environment for long periods of time. <P>SOLUTION: In a chromium-free surface treated steel sheet, on the surface of a galvanized steel sheet or an aluminum plated steel sheet, a surface treatment film is formed from a surface treatment composition obtained by compositely adding an organic phosphoric acid compound and an inorganic phosphoric acid compound at a prescribed ratio to a titanium-based aqueous liquid obtained by mixing a specific titanium compound with a hydrogen peroxide solution. The chromium-free surface treated steel sheet further has, on an upper layer of the surface treatment film, an upper layer film formed by coating and drying a coating material composition including a specified high molecular weight epoxy group-containing resin, a hardener having a group crosslinked with a hydroxyl group, a non-chromium based rust preventive additive and a solid lubricant containing a crystalline layered double hydroxide represented as [M<SP POS="POST">2+</SP><SB POS="POST">1-x</SB>M<SP POS="POST">3+</SP><SB POS="POST">x</SB>(OH)<SB POS="POST">2</SB>][A<SP POS="POST">n-</SP>]<SB POS="POST">x/n</SB>-zH<SB POS="POST">2</SB>O. <P>COPYRIGHT: (C)2012,JPO&INPIT |
