Abstract: An object is to provide, for example, a method for manufacturing a film-forming substrate that can sufficiently improve both bleeding of a resin composition and adhesion between the resin composition and a metal substrate surface. For example, provided is a method for manufacturing a film-forming substrate having a film of a resin composition formed on a metal substrate surface, the method including: an etching step of etching a metal substrate surface with a micro-etching agent; a surface treatment step of bringing the etched metal substrate surface into contact with a surface treatment agent to perform a surface treatment such that a contact angle of water on the surface is 50° or more and 150° or less; and a film forming step of forming a film of a resin composition on the surface-treated metal substrate surface by an inkjet method.

Abstract: The invention relates to a washing solution for a tin plating film after electroless tin plating and before water washing. The invention also relates to a method for forming a tin plating film, the method includes a step of washing step using the washing solution. The washing solution according to the present invention is an acidic aqueous solution containing an acid, a complexing agent, a stabilizer and a chloride ion. The washing solution has a chloride ion concentration of 2 wt % or more, and a tin concentration of 0.5 wt % or less. The washing solution according to the present invention has good washing property for a tin plating film surface, and allows a tin plating film to easily maintain its properties. In addition the washing solution causes little influence on a tin plating film surface even when continuously used and is excellent in temporal stability.