Corrosion inhibitor composition for magnesium or magnesium alloys

Abstract

The present invention relates to novel corrosion inhibitor compositions for magnesium or magnesium alloys and to a process for inhibiting the corrosion of such metals using such compositions. The corrosion inhibitor composition comprises a compound comprising a carboxyl group preventing the re-deposition of noble impurities which significantly decreases the corrosion rate by complexing said noble impurities, e.g. iron, nickel and copper.

1 . An article made of magnesium or a magnesium alloy coated with a coating composition comprising at least one corrosion inhibiting compound of Formula (1): 
       
         
           
           
               
               
           
         
         wherein R 4  is one or more substituents selected from the group consisting of hydroxy; alkyl, wherein the alkyl group is optionally substituted with one or more substituents selected from hydroxy and carboxy; carboxy; —SO 3 H and —NH 2 , and salts thereof; or the coating composition comprises 3,5-dinitro salicylic acid or salts thereof as at least one corrosion inhibiting compound. 
       
     
     
         2 . The article of  claim 1 , wherein the compound of Formula (1) is selected from the group consisting of 3-methylsalicylic acid, 4-methylsalicylic acid, 5-methylsalicylic acid, 6-methylsalicylic acid, 3-sulfosalicylic acid, 4-sulfosalicylic acid, 5-sulfosalicylic acid, 6-sulfosalicylic acid, 3-aminosalicylic acid, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 3,5-dinitro salicylic acid and salts thereof. 
     
     
         3 . The article of  claim 2 , wherein the compound of Formula (1) is selected from the group consisting of 4-aminosalicylic acid, 5-aminosalicylic acid, 5-methylsalicylic acid, 3,5-dinitro salicylic acid and salts thereof 
     
     
         4 . The article of  claim 1 , wherein the salts of compounds of Formula (1) are selected from their alkali metal or earth alkaline metal salts. 
     
     
         5 . The article of  claim 1 , wherein the corrosion inhibiting compound is present in cavities of porous nano- or microparticles distributed within the coating. 
     
     
         6 . The article of  claim 1 , wherein the corrosion inhibiting compound is present in micro- and nano-pores produced on the surface of magnesium or magnesium alloys. 
     
     
         7 . The article of  claim 6 , wherein the corrosion inhibiting compounds are incorporated in nano- and microparticles distributed in micro- and nano-pores produced on the surface of magnesium or magnesium alloys. 
     
     
         8 . A method for inhibiting the corrosion of magnesium or magnesium alloys comprising the steps of:
 a) providing magnesium or a magnesium alloy and   b) coating the magnesium or magnesium alloy with a corrosion inhibiting coating comprising at least one corrosion inhibiting compound of Formula (1):   
       
         
           
           
               
               
           
         
         wherein R 4  is one or more substituents selected from the group consisting of hydroxy; alkyl, wherein the alkyl group is optionally substituted with one or more substituents selected from hydroxy and carboxy; carboxy; —SO 3 H and −NH 2 , and salts thereof; or the coating composition comprises 3,5-dinitro salicylic acid or salts thereof as at least one corrosion inhibiting compound. 
       
     
     
         9 . The method of  claim 8 , further comprising a step a1) between steps a) and b), wherein in step a1) the magnesium or magnesium alloy is pretreated with the corrosion inhibiting composition.