Surface Treatment Agent, Method for Producing Aluminum Alloy Material for Cans, Said Aluminum Alloy Material Having Surface-Treated Coating Film, and Aluminum Alloy Can Body and Can Lid Using Same

An object of the present invention is to provide a surface treatment agent capable of forming a surface-treated coating having excellent corrosion resistance and adhesiveness on/over the surface of an aluminum alloy material for forming cans. The object is achieved by the surface treatment agent to be used for surface treatment of an aluminum alloy material for forming cans, which includes zirconium, aluminum, a nitrate radical, and fluorine, whereinthe pH ranges from 2.0 to 4.0,the molar mass concentration of the zirconium ranges from 3.2 mmol/kg to 33.0 mmol/kg,the molar mass concentration of the aluminum ranges from 14.8 mmol/kg to 74.1 mmol/kg,the molar mass concentration of the nitrate radical ranges from 16.1 mmol/kg to 161.4 mmol/kg,the molar mass concentration of the fluorine ranges from 52.6 mmol/kg to 526.3 mmol/kg,(F-6Zr)/Al≥2.5 (wherein, F represents the molar mass concentration of the fluorine, Zr represents the molar mass concentration of the zirconium, and Al represents the molar mass concentration of the aluminum.) is satisfied, and substantially no phosphorus compound is contained.