Abstract: Provided is a rust-preventive composition showing excellent rust-preventive performance for plate joining parts such as doors of automotive bodies, the composition having sufficient corrosion resistance and being capable of preventing dripping from automotive bodies. A rust-preventive composition including: a rust-preventive additive; a wax having a melting point within the range of 60° C. to 130° C. selected from microcrystalline waxes and polyethylene-based or polypropylene-based synthetic waxes; bentonite; a hydrogenated oil; and two or more kinds of diluents having different viscosities; the rust-preventive additive being contained in an amount within the range of 12% by mass to 39% by mass with respect to the total composition, the bentonite being contained in an amount within the range of 2% by mass to 6% by mass with respect to the total composition, the wax being contained in an amount within the range of 3% by mass to 13% by mass with respect to the total composition.

Abstract: A hydrophilic film is formed on the surface of a metal material, inhibits the growth of condensation water, and provides mold resistance, and a hydrophilization treatment agent is used for forming the hydrophilic film. The hydrophilization treatment agent has one or more compounds selected from poorly water-soluble cerium compounds; and a hydrophilic film prepared from the hydrophilization treatment agent. The poorly water-soluble cerium compounds are one or more compounds selected from cerium carbonate, cerium fluoride, cerium fluoride, and cerium oxide. By forming the hydrophilic film on the surface of a metal material, the growth of condensation water can be inhibited, and the mold resistance can be provided.

Abstract: A hydrophilizing agent that maintains a favorable wettability for dew condensation even after a long-term use; a hydrophilizing method; and an aluminum-containing metal material treated by the hydrophilizing method and having excellent wettability for dew condensation are provided. The hydrophilizing agent contains a modified polyvinyl alcohol obtained by graft polymerization of at least one type of N-vinyl lactam onto polyvinyl alcohol, thereby having a polymer and/or copolymer of the N-vinyl lactam in a side chain and a water-soluble cross-linking agent which can bind to a lactam moiety and/or a hydroxyl group of the modified polyvinyl alcohol. By applying and drying the hydrophilizing agent, a hydrophilic film having excellent wettability for dew condensation is formed.