Method for manufacturing a bonded body of galvanized steel sheet and adherend

A method for manufacturing a bonded body of a galvanized steel sheet and an adherend, consisting of:

• a surface treatment step of performing a liquid treatment for creating, on the surface of a galvanized steel sheet, micron-scale roughness having a peak-valley average spacing (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, forming ultra-fine irregularities having a period of 10 to 300 nm within the surface having the micron-scale roughness, and making the surface layer into a layer of a metal oxide or a metal phosphate, wherein the liquid treatment performed in said surface treatment step is:
• to perform a degreasing treatment of immersing the galvanized steel sheet in a degreasing solution for aluminum;
• and then,
• to perform a conversion treatment selected from the group consisting of:
• (1) a chromate treatment;
• (2) a zinc phosphate treatment;
• and (3) a zinc calcium phosphate treatment;
• an inserting step of inserting the galvanized steel sheet, having undergone said surface treatment step, into an injection molding mold;
• and
• an integrating step of injecting a thermoplastic resin composition having, as a main component, one or more selected from among polybutylene terephthalate, polyphenylene sulfide and an aromatic polyamide, onto the surface of said inserted galvanized steel sheet, and curing the injected thermoplastic resin composition after having penetrated into said ultra-fine irregularities, to thereby strongly integrate said galvanized steel sheet and a molded article of the thermoplastic resin composition.

A method for manufacturing a bonded body of a zinc-aluminum alloy coated steel sheet and an adherend, consisting of:

• a surface treatment step of performing a liquid treatment for creating, on the surface of a zinc-aluminum alloy coated steel sheet, micron-scale roughness having a peak-valley average spacing (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, forming ultra-fine irregularities having a period of 10 to 300 nm within the surface having the micron-scale roughness, and making the surface layer into a layer of a metal oxide or a metal phosphate, wherein the liquid treatment performed in said surface treatment step is:
• to perform a degreasing treatment of immersing the zinc-aluminum alloy coated steel sheet in a degreasing solution for aluminum;
• and then
• to perform chemical etching of immersing the sheet in an acidic aqueous solution of pH 1 to 3, and then,
• to perform one conversion treatment selected from the group consisting of:
• (1) a chromate treatment, (2) a zinc phosphate treatment, and (3) a zinc calcium phosphate treatment,
• an inserting step of inserting the zinc-aluminum alloy coated steel sheet, having undergone said surface treatment step, into an injection molding mold;
• and
• an integrating step of injecting a thermoplastic resin composition having, as a main component, one or more selected from among polybutylene terephthalate, polyphenylene sulfide and an aromatic polyamide, onto the surface of said inserted zinc-aluminum alloy coated steel sheet steel sheet, and curing the injected thermoplastic resin composition after having penetrated into said ultra-fine irregularities, to thereby strongly integrate said zinc-aluminum alloy coated steel sheet and a molded article of the thermoplastic resin composition.