Metal connection member and method for chemical conversion treatment of metal connection member

Abstract

A metal connection member including a Mg alloy member composed principally of magnesium, a partner member connected to the Mg alloy member, the partner member being composed principally of a metal nobler than magnesium, and a chemical conversion treatment film that covers a surface of the Mg alloy member and a surface of the partner member with covering a boundary between the Mg alloy member and the partner member.

1 . A metal connection member comprising:
 a Mg alloy member composed principally of magnesium;   a partner member connected to the Mg alloy member, the partner member being composed principally of a metal nobler than magnesium; and   a chemical conversion treatment film that covers a surface of the Mg alloy member and a surface of the partner member with covering a boundary between the Mg alloy member and the partner member.   
     
     
         2 . The metal connection member according to  claim 1 , wherein the charge transfer resistance of the Mg alloy member in 1 M of Na 2 SO 4  is 300 Ω or more and 1200 Ω or less. 
     
     
         3 . The metal connection member according to  claim 1 , wherein the content of aluminum in the Mg alloy member is 0.3% by mass or more and 12.0% by mass or less. 
     
     
         4 . A method for a chemical conversion treatment of a metal connection member, the method comprising:
 a preparation step of preparing a metal connection member, the metal connection member including a Mg alloy member composed principally of magnesium and a partner member connected to the Mg alloy member, the partner member being composed principally of a metal nobler than magnesium; and,   a chemical conversion treatment step of bringing both of the Mg alloy member and the partner member included in the metal connection member into contact with a chemical conversion treatment liquid in a collective manner to form a chemical conversion treatment film on a surface of the metal connection member,   wherein the electric conductivity y of the chemical conversion treatment liquid satisfies at least one of the relation formulae (a) and (b) below,
     y≤ 0.0007  x   1 +14.0   (a)
 
     y≤ 0.054  x   2 +14.2   (b)
 
   
       where x 1  (Ω) is the charge transfer resistance of the Mg alloy member in 1M of Na 2 SO 4 , x 2  (mass %) is the content of aluminum in the Mg alloy member, and y (mS/cm) is the electric conductivity of the chemical conversion treatment liquid. 
     
     
         5 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the charge transfer resistance x 1  is 300 Ω or more and 1200 Ω or less. 
     
     
         6 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the content of aluminum x 2  is 0.3% by mass or more and 12.0% by mass or less. 
     
     
         7 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the electric conductivity y of the chemical conversion treatment liquid satisfies 0.1 mS/cm≤y. 
     
     
         8 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the content of zinc in the Mg alloy member is 0.5% by mass or more and 6.2% by mass or less. 
     
     
         9 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the pH of the chemical conversion treatment liquid is 2.0 or more and 7.0 or less. 
     
     
         10 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the pH and the electric conductivity y of the chemical conversion treatment liquid are adjusted using at least one acid or salt selected from nitric acid, sulfuric acid, hydrofluoric acid, hydrofluosilicic acid, bromic acid, manganic acid, permanganic acid, vanadic acid, hydrogen peroxide, an organic acid, and salts of these acids. 
     
     
         11 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the chemical conversion treatment liquid includes an element belonging to Group 4 of the periodic table. 
     
     
         12 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the temperature of the chemical conversion treatment liquid is 5° C. or more and 70° C. or less. 
     
     
         13 . The method for a chemical conversion treatment of a metal connection member according to  claim 4 , wherein the Mg alloy member and the partner member are electrically connected to each other.