Method for the surface treatment of corten steel

Abstract

The present invention relates to a method for the surface treatment of Corten steel, in particular comprising the steps of cleaning, activating, coloring, and sealing the surface. The invention further relates to Corten steels produced by the method according to the invention.

1 . A method for the surface treatment of Corten steel, comprising the following steps:
 (i) providing Corten steel and carrying out a treatment comprising the following stages:   (1) cleaning at least a portion of at least one surface of the Corten steel, thereby forming a cleaned surface;   (2) activating at least a portion of the cleaned surface of the Corten steel from stage (1) by bringing the cleaned surface into contact with an aqueous activating solution containing fluoride ions, one or more oxidizing agents, and optionally one or more stabilizers for the oxidizing agent(s), thereby forming an activated surface; and   (3) coloring at least a portion of the activated surface of the Corten steel from stage (2) by treating the activated surface with water for a period of at least 30 minutes and until the desired coloration of the surface of the Corten steel is achieved, thereby forming a colored surface; and   (ii) sealing at least a portion of the colored surface from stage (3) of step (i) by applying a colorless, transparent coating, thereby forming a surface-treated Corten steel.   
     
     
         2 . The method according to  claim 1 , wherein the Corten steel comprises: iron as the main component, and one or more components selected from the group consisting of carbon in a proportion of 0 to 0.16% by weight, chromium in a proportion of 0.40 to 0.65% by weight, silicon in a proportion of 0.30 to 0.50% by weight, manganese in a proportion of 0.80 to 1.25% by weight, phosphorus in a proportion of 0 to 0.030% by weight, sulfur in a proportion of 0 to 0.030% by weight, copper in a proportion of 0.10 to 0.40% by weight, vanadium in a proportion of 0.02 to 0.10% by weight, and nickel in a proportion of 0 to 0.40% by weight. 
     
     
         3 . The method according to  claim 1 , wherein the cleaning in stage (1) of step (i) takes place in such a way that the cleaned surface of the Corten steel is metallically clean, free of grease, and free of rust. 
     
     
         4 . The method according to  claim 1 , wherein the aqueous activating solution contains fluoride ions in a quantity of greater than 0% by weight and less than or equal to 3% by weight, and/or the aqueous activating solution contains the oxidizing agent(s) in a quantity of greater than 0% by weight and less than or equal to 20% by weight. 
     
     
         5 . The method according to  claim 1 , wherein the treatment of the activated surface in stage (3) of step (i) is carried out with water over a period of between 30 minutes and 15 hours, up to the desired color of the surface. 
     
     
         6 . The method according to  claim 1 , further comprising rinsing the active surface with water in stage (2) from step (i), and wherein the coloring of the activated surface in stage (3) of step (i) is carried out by spraying and the activated surface is kept moist. 
     
     
         7 . The method according to  claim 1 , wherein the sealing in step (ii) takes place using a sol-gel coating, the sol-gel coating being burned in after the application in order to achieve a glass ceramic structure. 
     
     
         8 . The method according to  claim 1 , wherein at least a portion of the quantity of fluoride ions originates from hydrogen fluoride which has been added to the aqueous activating solution. 
     
     
         9 . A Corten steel having a colorless, transparent coating on a colored surface, with the exception of rust brown, of the Corten steel, wherein the surface has been treated by a method comprising:
 (i) carrying out a treatment comprising the following stages:
 (1) cleaning at least a portion of at least one surface of the Corten steel, thereby forming a cleaned surface; 
 (2) activating at least a portion of the cleaned surface of the Corten steel from stage (1) by bringing the cleaned surface into contact with an aqueous activating solution containing fluoride ions, one or more oxidizing agents, and optionally one or more stabilizers for the oxidizing agent(s), thereby forming an activated surface; and 
 (3) coloring at least a portion of the activated surface of the Corten steel from stage (2) by treating the activated surface with water for a period of at least 30 minutes and until the desired coloration of the surface of the Corten steel is achieved, thereby forming a colored surface; and 
   (ii) sealing at least a portion of the colored surface from stage (3) of step (i) by applying a colorless, transparent coating, thereby forming a surface-treated Corten steel, and wherein the sealing step (ii) takes place using a sol-gel coating, the sol-gel coating being burned in after the application in order to achieve a glass ceramic coating.   
     
     
         10 . The method according to  claim 2 , wherein the cleaning in stage (1) of step (i) takes place in such a way that the cleaned surface of the Corten steel is metallically clean, free of grease, and free of rust.