Process for the anticorrosion treatment of a solid metal substrate and treated solid metal substrate capable of being obtained by such a process

Abstract

An anticorrosion treatment process in which applied to an oxidizable surface of a solid metal substrate is a liquid solution, referred to as treatment solution, including: at least one alkoxysilane, and at least one cerium (Ce) cation; in a liquid aqueous-alcoholic composition, the treatment solution being suitable for being able to form, at the surface of the solid metal substrate, a hybrid matrix by hydrolysis/condensation of each alkoxysilane(s) and of each cerium (Ce) cation; the treatment solution having a molar ratio (Si/Ce) of silicon element of the alkoxysilane(s) with respect to the cerium (Ce) cation(s) of between 50 and 500; characterized in that the cerium (Ce) cation(s) has(have) a concentration between 0.005 mol/L and 0.015 mol/L in the treatment solution.

1 . A process for anticorrosion treatment in which there is applied to an oxidizable surface of a solid metal substrate a liquid solution, called a treatment solution, comprising:
 at least one alkoxysilane, and   at least one cerium (Ce) cation;   
       in a liquid hydroalcoholic composition, said treatment solution being adapted to be able to form a hybrid matrix on the surface of the solid metal substrate by hydrolysis/condensation of each alkoxysilane and of each cerium (Ce) cation; 
       the treatment solution having a molar ratio (Si/Ce) of silicon element of the alkoxysilane(s) to the cerium (Ce) cation(s) of between 50 and 500; 
       wherein the cerium (Ce) cation(s) has(have) a concentration of between 0.005 mol/1 and 0.015 mol/l in the treatment solution. 
     
     
         2 . The process as claimed in  claim 1 , wherein each alkoxysilane is chosen from the group formed of:
 the tetraalkoxysilanes of the general formula (I) below:
   Si(O—R 1 ) 4   (I)
 
   
       wherein:
 Si is the element silicon, O is the element oxygen; 
 R 1  is chosen from the group formed of:
 a hydrocarbon group of the formula [—C n H 2n+1 ], n being an integer greater than or equal to 1; and 
 the group 2-hydroxyethyl (HO—CH 2 —CH 2 —); and 
 an acyl group of the general formula —CO—R′ 1  wherein R′ 1  is a hydrocarbon group of the formula [—C n H 2n+1 ], n being an integer greater than or equal to 1; and 
 
 the alkoxysilanes of the general formula (II) below:
   Si(O—R 2 ) 4−a (R 3 ) a   (II)
 
 
 
       wherein:
 R 2  is chosen from the group formed of:
 a hydrocarbon group of the formula [—C n H 2n+1 ], n being an integer greater than or equal to 1; and 
 the group 2-hydroxyethyl (HO—CH 2 —CH 2 —); and 
 an acyl group of the general formula —CO—R′ 1  wherein R′ 1  is a hydrocarbon group of the formula [—C n H 2n+1 ], n being an integer greater than or equal to 1; and 
 
 R 3  is an organic group bonded to the silicon element (Si) of the alkoxysilane by an Si—C bond; 
 a is a natural integer of the interval]0; 4[. 
 
     
     
         3 . The process as claimed in  claim 1 , wherein the treatment solution comprises at least one metal alkoxide. 
     
     
         4 . The process as claimed in  claim 3 , wherein each metal alkoxide has the general formula (VII) below:
   M′(O—R 9 ) n″   (VII)
   
       wherein:
 M′ is a metal element chosen from the group formed of aluminum (Al), vanadium (V), titanium (Ti) and zirconium (Zr); 
 R 9  is an aliphatic hydrocarbon group of the formula [—C n H 2n+1 ] wherein n is an integer greater than or equal to 1; and 
 n″ is a natural integer representing the valence of the metal element M′. 
 
     
     
         5 . The process as claimed in  claim 3 , wherein each metal alkoxide is an aluminum alkoxide of the general formula (III) below:
   Al(OR 4 ) n   (III)
   
       wherein:
 Al and O are the elements aluminium and oxygen, respectively; and 
 R 4  is an aliphatic hydrocarbon group having from 1 to 10 carbon atoms; 
 n is a natural integer representing the valence of the aluminum element (Al). 
 
     
     
         6 . The process as claimed in  claim 1 , wherein the solid metal substrate is formed of a material chosen from the group formed of the oxidizable materials. 
     
     
         7 . The process as claimed in  claim 1 , wherein, before application of the treatment solution, said oxidizable surface of the solid metal substrate is immersed in a liquid solution, called a conversion solution, formed of at least one corrosion inhibitor in water, said corrosion inhibitor being chosen from the group formed of the lanthanide cations, and said oxidizable surface of the solid metal substrate is kept in contact with the conversion solution for a period of time adapted to form a conversion layer formed of said lanthanide bonded by at least one covalent bond to the oxidizable surface and extending over the surface of the solid metal substrate. 
     
     
         8 . The process as claimed in  claim 7 , wherein the conversion solution has a concentration of corrosion inhibitor of between 0.001 mol/1 and 0.5 mol/l. 
     
     
         9 . The process as claimed in  claim 1 , wherein the treatment solution is applied by dip-coating of the solid metal substrate in said treatment solution. 
     
     
         10 . The process as claimed in  claim 1 , wherein the treatment solution is applied by atmospheric spray-coating of the treatment solution on the surface of the solid metal substrate. 
     
     
         11 . The process as claimed in  claim 1 , wherein the hydroalcoholic composition is formed of water and at least one alcohol. 
     
     
         12 . The process as claimed in  claim 1 , wherein the cerium cation of the treatment solution is chosen from the group formed of the cerium chlorides and cerium nitrates. 
     
     
         13 . The process as claimed in  claim 4 , wherein each metal alkoxide is an aluminum alkoxide of the general formula (III) below:
   Al(OR 4 ) n   (III)
   
       wherein:
 Al and O are the elements aluminium and oxygen, respectively; and 
 R 4  is an aliphatic hydrocarbon group having from 1 to 10 carbon atoms; 
 n is a natural integer representing the valence of the aluminum element (Al).