Methods of removing rust from a ferrous metal-containing surface

Abstract

Disclosed are methods for removing rust from a ferrous metal-containing surface. These methods include contacting the surface with a composition that includes a carboxylic acid, a synthetic hectorite clay, and water.

1 . A method for removing rust from a ferrous metal-containing surface comprising contacting the surface with a composition comprising:
 (a) a carboxylic acid;   (b) a synthetic hectorite clay; and   (c) water.   
     
     
         2 . A ferrous metal-containing surface treated by the method of  claim 1 . 
     
     
         3 . The method of  claim 1 , wherein the rust comprises an iron oxide and/or iron hydroxide. 
     
     
         4 . The method of  claim 1 , wherein the ferrous metal comprises steel. 
     
     
         5 . The method of  claim 1 , wherein the steel comprises mild steel. 
     
     
         6 . The method of  claim 1 , wherein the carboxylic acid comprises an aliphatic hydroxy acid. 
     
     
         7 . The method of  claim 6 , wherein the aliphatic hydroxyl acid comprises citric acid. 
     
     
         8 . The method of  claim 1 , wherein the carboxylic acid is present in the composition in an amount of at least 10 percent by weight and no more than 30 percent by weight, based on the total weight of the composition. 
     
     
         9 . The method of  claim 1 , wherein the synthetic hectorite clay has the chemical formula NaO 3 (Mg, Li) 3 Si 4 O 10 (F, OH) 2 . 
     
     
         10 . The method of  claim 1 , wherein the average diameter of the synthetic hectorite is 1 to 30 nanometers. 
     
     
         11 . The method of  claim 1 , wherein the synthetic hectorite clay is present in the composition in an amount of at least 1 percent by weight and no more than 10 percent by weight, based on the total weight of the composition. 
     
     
         12 . The method of  claim 1 , wherein the composition further comprises a source of chloride ions. 
     
     
         13 . The method of  claim 1 , wherein the composition has a low shear viscosity of at least 1,000 Pa·s and a high shear viscosity of no more than 0.50 Pa·s. 
     
     
         14 . The method of  claim 13 , wherein the composition has a low shear viscosity of at least 4,000 Pa·s and a high shear viscosity of no more than 0.01 Pa·s. 
     
     
         15 . The method of  claim 1 , wherein the composition has a pH of no more than 6.0. 
     
     
         16 . The method of  claim 1 , wherein the contacting comprises spraying the composition onto the metal containing surface. 
     
     
         17 . The method of  claim 17 , wherein the ferrous-metal containing surface is oriented substantially vertically. 
     
     
         18 . A method for removing rust from a ferrous metal-containing surface comprising spray applying a composition onto at least a portion of the ferrous metal-containing surface, the composition comprising:
 (a) a carboxylic acid;   (b) a synthetic hectorite clay; and   (c) water,   wherein (i) the ferrous metal-containing surface is oriented substantially vertically, and (ii) the composition has a low shear viscosity of at least 1,000 Pa·s and a high shear viscosity of no more than 0.50 Pa·s.   
     
     
         19 . The method of  claim 18 , wherein the composition further comprises a source of chloride ions. 
     
     
         20 . The method of  claim 18 , wherein the carboxylic acid comprises citric acid.