Method of chemical treatment and chemically treated member

Abstract

A chemical treatment method in which an object to be treated is treated with a chemical treating agent to form a chemical conversion coating, in which the object to be treated has at least one aluminum-plated steel sheet and at least one member selected from the group consisting of cold-rolled steel sheets, zinc-plated steel sheets, and aluminum sheets and the chemical treating agent is one which has zirconium, fluorine, and an aminated silane coupling agent and in which the zirconium content is 100-700 ppm in terms of metal amount and the fluorine/zirconium ratio is 3.5-7.0 by mole. A sufficient coating amount can be ensured on the surface of a zinc deposit, cold-rolled steel sheet, zinc-plated steel sheet, aluminum-plated steel sheet, or the like and a chemical conversion coating having sufficient base-hiding properties and sufficient adhesion can be formed.

1 - 6 . (canceled) 
   
   
       7 . A method of a chemical conversion treatment for forming a chemical conversion coating film comprising treating an object with a chemical conversion treatment agent, wherein
 the object includes at least one aluminum coated steel plate, and at least one selected from the group consisting of a cold-rolled steel plate, a galvanized steel plate, and an aluminum plate;   the chemical conversion treatment agent comprises zirconium, fluorine, and an amino group-containing silane coupling agent;   the content of zirconium with respect to metal content in the chemical conversion treatment agent is no less than 100 ppm and no greater than 700 ppm; and   the molar ratio of fluorine to zirconium is no less than 3.5 and no greater than 7.0.   
   
   
       8 . The method of a chemical conversion treatment according to  claim 7  wherein the content of the amino group-containing silane coupling agent in the chemical conversion treatment agent is no less than 50 ppm and no greater than 500 ppm with respect to the solid content. 
   
   
       9 . The method of a chemical conversion treatment according to  claim 7  wherein the pH of the chemical conversion treatment agent is no less than 2.6 and no greater than 4.5. 
   
   
       10 . The method of a chemical conversion treatment according to  claim 8  wherein the pH of the chemical conversion treatment agent is no less than 2.6 and no greater than 4.5. 
   
   
       11 . The method of a chemical conversion treatment according to  claim 7  wherein the chemical conversion treatment agent further comprises at least one agent for imparting adhesiveness and corrosion resistance selected from the group consisting of a magnesium ion, a zinc ion, a calcium ion, an aluminum ion, a gallium ion, an indium ion, and a copper ion. 
   
   
       12 . The method of a chemical conversion treatment according to  claim 7  wherein the object is a member for an automotive body, and an automotive body. 
   
   
       13 . A member subjected to a chemical conversion treatment comprising a conversion coating film formed by the method of the chemical conversion treatment according to  claim 7 .