Modified sheet silicates as corrosion protection

Abstract

Use of modified sheet silicates (a) in combination with at least one polycationic polymer (b) for protecting metallic surfaces against corrosion. Metallic surfaces which are protected against corrosion by means of modified sheet silicates (a) in combination with at least one polycationic polymer (b). Method of protecting metallic surfaces against corrosion, which comprises applying formulations to the metallic surface to be protected. Anticorrosion composition comprising modified sheet silicates (a) and at least one polycationic polymer (b).

1 . The use of modified sheet silicates (a) in combination with at least one polycationic polymer (b) for protecting metallic surfaces against corrosion. 
     
     
         2 . The use according to  claim 1 , wherein the modified sheet silicates (a) have an average particle size of from 50 nm to 50 μm. 
     
     
         3 . The use according to  claim 1  or  2 , wherein the modified sheet silicates (a) have a platelet-like particle shape. 
     
     
         4 . The use according to any of  claims 1  to  3 , wherein the zeta potential of the modified sheet silicates (a) in the presence of the at least one polycationic polymer (b) in the pH range from 4 to 13 is at least −2, measured in the aqueous phase at 25° C. 
     
     
         5 . The use according to any of  claims 1  to  4 , wherein the weight ratio of the at least one polycationic polymer (b) to modified sheet silicate (a) is from 1:1000 to 2:1. 
     
     
         6 . The use according to any of  claims 1  to  5 , wherein the modified sheet silicates (a) comprise sheet silicates selected from among the natural sheet silicates antigorite, kaolinite, halloysite, saponite, talc, pyrophyllite, hectorite, montmorillonite, bentonite, vermiculite, muscovite, biotite and mixtures thereof. 
     
     
         7 . The use according to any of  claims 1  to  6 , wherein the modified sheet silicates (a) are hydrophobically modified. 
     
     
         8 . The use according to any of  claims 1  to  7 , wherein the at least one polycationic polymer (b) is selected from among polyamines, polyimines, polyamides, polydiallyldimethylammonium chloride, polyvinylamine, polyvinylpyridine, polyvinylimidazole and polyvinylpyrrolidone and also natural and semisynthetic polymers including cationically modified starches and mixtures thereof. 
     
     
         9 . The use according to  claim 8 , wherein the at least one polycationic polymer (b) is polyethylenimine. 
     
     
         10 . The use according to any of  claims 1  to  9 , wherein the at least one polycationic polymer (b) has a number average molecular weight of from 500 g/mol to 2 000 000 g/mol. 
     
     
         11 . The use according to any of  claims 1  to  10 , wherein the at least one polycationic polymer (b) is a hyperbranched polymer or dendrimer having a degree of branching (DB) greater than 10%. 
     
     
         12 . The use according to any of  claims 1  to  11 , wherein the modified sheet silicates (a) and the at least one polycationic polymer (b) are used in an application medium in a total concentration of at least 0.1% by weight, based on the total amount of (a), (b) and application medium. 
     
     
         13 . A metallic surface which is protected against corrosion by means of modified sheet silicates (a) in combination with at least one polycationic polymer (b) as defined in any of  claims 1  to  12 . 
     
     
         14 . A method of protecting metallic surfaces against corrosion, which comprises the steps:
 i) provision of a formulation comprising modified sheet silicates (a) and at least one polycationic polymer (b) as defined in any of  claims 1  to  12  and an application medium,   ii) application of the formulation to the metallic surface to be protected and   iii) optionally drying and/or heat treatment of the surface.   
     
     
         15 . An anticorrosion composition comprising:
 i) from 0.1 to 3% by weight of modified sheet silicates (a) and at least one polycationic polymer (b) as defined in any of  claims 1  to  12 , where the weight ratio of (b) to (a) is from 1:1000 to 2:1,   ii) from 97 to 99.9% by weight of liquid dispersion medium,   iii) from 0 to 5% by weight of at least one inorganic salt selected from among phosphates and fluorides of Li, Na, K, Mg, Ca, Ba, Zn, Mn, Fe, Ti and Zr,   
       based on the total amount of the anticorrosion composition. 
     
     
         16 . An anticorrosion composition comprising:
 i) from 0.1 to 3% by weight of modified sheet silicates (a) and at least one polycationic polymer (b) as defined in any of  claims 1  to  12 , where the weight ratio of (b) to (a) is from 1:1000 to 2:1,   ii) from 0.1 to 30% by weight of at least one emulsifier,   iii) from 5 to 90% by weight of liquid dispersion medium,   iv) from 0 to 5% by weight of at least one inorganic salt selected from among phosphates and fluorides of Li, Na, K, Mg, Ca, Ba, Zn, Mn, Fe, Ti and Zr,   
       based on the total amount of the anticorrosion composition. 
     
     
         17 . The anticorrosion composition according to  claim 15  or  16 , wherein the modified sheet silicates (a) comprise antigorite, kaolinite, halloysite, saponite, talc, pyrophyllite, hectorite, montmorillonite, bentonite, vermiculite, muscovite, biotite and the at least one polycationic polymer (b) is polyethylenimine.