Acid cleaning and corrosion inhibiting compositions comprising gluconic acid

Abstract

A biodegradable acid cleaning composition for cleaning stainless steel, and other surfaces is disclosed. The composition comprises urea sulfate in combination with gluconic acid which serves as a corrosion inhibitor. The composition retains the cleaning and corrosion prevention properties of similar phosphoric acid solutions but is safe for the environment and is less expensive to produce. Applicants have surprisingly found that the traditionally alkaline corrosion inhibitor, gluconic acid, can work effectively in an acidic cleaning composition.

1 . A corrosion inhibiting composition with a pH of less than 7 and comprising sulfuric acid, urea, water, and a corrosion inhibiting amount of gluconic acid, wherein said urea and sulfuric acid have a molar ratio of about 1 to 2 to create urea sulfate. 
     
     
         2 . The composition of  claim 1  wherein said gluconic acid to urea sulfate is at least about 0.012% to 25% by weight of the solution. 
     
     
         3 . The composition of  claim 1  wherein said about 5 to about 75 weight percent urea, about 5 to about 85 weight percent sulfuric acid, and about 0 to about 75 weight percent water. 
     
     
         4 . The composition of  claim 3  wherein the urea/sulfuric acid molar ratio is greater than 2 or less than 1. 
     
     
         5 . The composition of  claim 3  wherein a portion of said urea and sulfuric acid are present as a member selected from the group consisting of monourea sulfate, diurea sulfate, and combinations thereof. 
     
     
         6 . The composition of  claim 1  comprising about 25% by weight urea sulfate and about 0.60 percent by weight of gluconic acid (50%). 
     
     
         7 . The composition of  claim 6  wherein said 25% by weight of urea sulfate comprises about 16% sulfuric acid (93%) and 11% urea. 
     
     
         8 . The composition of  claim 6  wherein said sulfuric acid (93%) is in an amount of 16.66%. 
     
     
         9 . The composition of  claim 8  wherein said urea is in an amount of about 11.50% by weight of solution. 
     
     
         10 . The composition of  claim 8  wherein water comprises about 70% of said solution. 
     
     
         11 . The composition of  claim 6  comprising the following components:
 sulfuric acid about 17% 
 urea about 11% 
 gluconic acid about 0.60% 
 
       with the remainder being water. 
     
     
         12 . The composition of  claim 11  comprising the following: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   water 
                   71% 
                 
                     
                   surfuric acid 
                   16.5% 
                 
                     
                   urea 
                   11.5 
                 
                     
                   gluconic acid 
                    0.60 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
               
            
           
         
       
     
     
         13 . The composition of  claim 1  further comprising one or more of the following: a dye, a sequestrant, a defoamer, or a preservative. 
     
     
         14 . A biodegradable, acid cleaning composition comprising the following: 
       
         
           
                 
                 
                 
               
                     
                     
                 
                     
                   water 
                   71% 
                 
                     
                   surfuric acid 
                   16.5% 
                 
                     
                   urea 
                   11.5% 
                 
                     
                   gluconic acid 
                    0.60%, 
                 
                     
                     
                 
             
                
               
               
                
                
                
                
                
               
            
           
         
         wherein said urea and sulfuric acid have a molar ratio of about 1 to 2 to create urea sulfate. 
       
     
     
         15 . The cleaning composition of  claim 14  further comprising: one or more of the following: a defoamer, a sequestrant, or a preservative.