Bonded body of galvanized steel sheet and adherend, and manufacturing method thereof

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

• 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 thin layer of a metal oxide or a metal phosphate;
• 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 galvanized steel sheet and an adherend, comprising:

• 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 thin layer of a metal oxide or a metal phosphate;
• a resin molded article production step of producing a resin molded article of a resin composition having, as a main component, one or more selected from among polybutylene terephthalate, polyphenylene sulfide, an aromatic polyamide, an aliphatic polyamide and a liquid crystal polymer;
• a heating step of heating the surface of the galvanized steel sheet, having undergone said surface treatment step, to a temperature not lower than a melting temperature of said resin composition;
• and
• a press-fusion bonding step of pressing said resin molded article against the surface of said galvanized steel sheet having undergone said heating step, to put the resin composition in a molten state, placing the galvanized steel sheet and the resin molded article under reduced pressure, increasing the pressure thereafter to cause the molten resin composition to penetrate into said ultra-fine irregularities, and curing the resin that has penetrated, to thereby fusion-bond the galvanized steel sheet and the resin molded article.

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

• 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 thin layer of a metal oxide or a metal phosphate;
• a coating step of coating one type of thermosetting adhesive selected from among (1) to (3), namely (1) an epoxy adhesive, (2) a phenolic adhesive and (3) an unsaturated polyester adhesive, onto the surface of the galvanized steel sheet having undergone said surface treatment step;
• a joining preliminary step of placing the galvanized steel sheet, having undergone said coating step, into a hermetic container that is depressurized and then pressurized to cause the applied thermosetting adhesive to penetrate into said ultra-fine irregularities;
• a fixing step of closely adhering and fixing an adherend to the surface of said galvanized steel sheet having undergone said joining preliminary step;
• and
• a curing step of heating said fixed galvanized steel sheet and adherend, to thereby cure the adhesive component.