Cleaning and conversion coating of hot rolled steel articles

Abstract

A process is disclosed in which hot rolled steel articles, such as rail car articles, LP tanks and barge articles are cleaned and conversion coated. The cleaning compositions comprise aqueous phosphoric acid, and the conversion coating compositions comprise aqueous phosphate.

What is claimed is:  
     
         1 . A process for treating a rail car article comprising hot rolled steel, wherein the process comprises: 
 acid spray cleaning the article with a solution comprising phosphoric acid,    applying a post-cleaning rinse to the article,    phosphate spraying the article with a solution comprising a phosphate, and    applying a post-phosphating rinse to the article.    
     
     
         2 . The process of  claim 1 , further comprising substantially containing mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         3 . The process of  claim 2 , wherein an air barrier is used to substantially contain mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         4 . The process of  claim 1 , wherein the article is sprayed for 1-6 minutes during the phosphate spraying stage.  
     
     
         5 . The process of  claim 1 , wherein the article is sprayed for 2-4 minutes during the phosphate spraying stage.  
     
     
         6 . The process of  claim 1 , wherein the acid spray pressure is 5-70 psig.  
     
     
         7 . The process of  claim 1 , wherein the acid spray pressure is 18-30 psig.  
     
     
         8 . The process of  claim 1 , wherein the phosphate spraying pressure is 5-70 psig.  
     
     
         9 . The process of  claim 1 , wherein the phosphate spraying pressure is 5-60 psig.  
     
     
         10 . The process of  claim 1 , wherein the article is at least partially rotated during at least some of the process.  
     
     
         11 . A process for treating a rail car article comprising hot rolled steel, wherein the process comprises: 
 acid spray cleaning the article for 4-8 minutes with a solution comprising phosphoric acid,    applying a post-cleaning rinse to the article,    phosphate spraying the article for 1-6 minutes with a solution comprising a phosphate, and    applying a post-phosphating rinse to the article.    
     
     
         12 . The process of  claim 11 , further comprising substantially containing mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         13 . The process of  claim 11 , wherein an air barrier is used to substantially contain mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         14 . The process of  claim 11 , wherein liquid is drained from the article after an application of spray and before an application of liquid in a subsequent stage.  
     
     
         15 . The process of  claim 11 , wherein the phosphate is sprayed to provide a phosphate coating thickness on the article of at least 50 mg/ft 2  when dried.  
     
     
         16 . The process of  claim 11 , wherein the phosphate is sprayed to provide a phosphate coating thickness on the article of 75-500 mg/ft 2  when dried.  
     
     
         17 . The process of  claim 11 , wherein the phosphate is sprayed to provide a phosphate coating thickness on the article of 75-150 mg/ft 2  when dried.  
     
     
         18 . The process of  claim 11 , wherein the acid spray temperature is 120-200° F.  
     
     
         19 . The process of  claim 11 , wherein the acid spray temperature is 140-170° F.  
     
     
         20 . The process of  claim 11 , wherein the phosphate spraying temperature is 80-150° F.  
     
     
         21 . The process of  claim 11 , wherein the phosphate spraying temperature is 120-130° F.  
     
     
         22 . The process of  claim 11 , wherein the article is at least partially rotated during at least some of the process.  
     
     
         23 . A process for treating a rail car article comprising hot rolled steel, wherein the process comprises: 
 acid spray cleaning the article for 4-8 minutes with a solution comprising phosphoric acid,    applying a post-cleaning spray rinse to the article,    phosphate spraying the article for 2-4 minutes with a solution comprising a phosphate,    applying a post-phosphating spray rinse to the article, and    drying and/or curing the article at 200-400° F.    
     
     
         24 . The process of  claim 23 , further comprising substantially containing mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         25 . The process of  claim 23 , wherein an air barrier is used to substantially contain mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         26 . The process of  claim 23  wherein the phosphate is sprayed to provide a phosphate coating thickness on the article of at least 50 mg/ft 2  when dried.  
     
     
         27 . The process of  claim 23 , wherein the phosphate is sprayed to provide a phosphate coating thickness on the article of 75-500 mg/ft 2  when dried.  
     
     
         28 . The process of  claim 23 , wherein the phosphate is sprayed to provide a phosphate coating thickness on the article of 75-150 mg/ft 2  when dried.  
     
     
         29 . A process for treating a rail car article comprising hot rolled steel, wherein the process comprises: 
 acid spray cleaning the article for 4-8 minutes with a solution comprising phosphoric acid,    applying a post-cleaning spray rinse to the article,    phosphate spraying the article for 2-4 minutes with a solution comprising a phosphate, and    applying a post-phosphating spray rinse to the article.    
     
     
         30 . The process of  claim 29 , further comprising substantially containing mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         31 . The process of  claim 29 , wherein an air barrier is used to substantially contain mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         32 . The process of  claim 31 , wherein the air barrier comprises a silhouettes.  
     
     
         33 . The process of  claim 31 , wherein the air barrier comprises an air knife.  
     
     
         34 . The process of  claim 31 , wherein the air barrier comprises a spray comprising water.  
     
     
         35 . The process of  claim 29 , wherein the acid is sprayed at a flow volume of about 1,000-3,000 gal/minute.  
     
     
         36 . The process of  claim 29 , wherein the phosphate is sprayed at a flow volume of about 1,000-3,000 gal/minute.  
     
     
         37 . The process of  claim 29 , wherein the article is conveyed along rail tracks and the spray is applied to the article as the article moves along the tracks, and wherein mist, spray and fumes of each stage are substantially contained from carrying over to other stages by air barriers located along the tracks, through which the articles are conveyed.  
     
     
         38 . The process of  claim 29 , wherein the post-cleaning spray rinse is sprayed at a flow volume of about 5-800 gal/minute.  
     
     
         39 . The process of  claim 29 , wherein the post-phosphating spray rinse is sprayed at a flow volume of about 5-800 gal/minute.  
     
     
         40 . The process of  claim 29 , further comprising the application of a chemical sealant to the article.  
     
     
         41 . A process for treating an article comprising hot rolled steel, wherein the process comprises: 
 acid spray cleaning the article for 1-8 minutes with a solution comprising phosphoric acid,    applying a post-cleaning rinse to the article, phosphate spraying the article with a solution comprising a phosphate, and    applying a post-phosphating rinse to the article.    
     
     
         42 . The process of  claim 41 , wherein the article comprises a rail car article.  
     
     
         43 . The process of  claim 41 , wherein the article comprises an LP tank article.  
     
     
         44 . The process of  claim 41 , wherein the article comprises an barge article.  
     
     
         45 . The process of  claim 41 , further comprising, after applying the post-phosphating spray rinse, drying and/or curing the article at 200-600° F.  
     
     
         46 . The process of  claim 41 , wherein mist, spray and fumes of each stage are substantially contained from carrying over to each of the other stages.  
     
     
         47 . The process of  claim 41 , wherein the article is sprayed for 1-6 minutes during the phosphate spraying stage.  
     
     
         48 . The process of  claim 41 , wherein liquid is drained from the article after an application of spray and before an application of liquid in a subsequent stage.  
     
     
         49 . The process of  claim 41 , wherein the article is sprayed for 2-4 minutes during the phosphate spraying stage.  
     
     
         50 . The process of  claim 41 , wherein the article is at least partially rotated during at least some of the process.  
     
     
         51 . A process for treating an LP tank article comprising hot rolled steel, wherein the process comprises: 
 acid spray cleaning the article for 4-8 minutes with a solution comprising phosphoric acid,    applying a post-cleaning spray rinse to the article,    phosphate spraying the article for 2-4 minutes with a solution comprising a phosphate,    applying a post-phosphating spray rinse to the article, and    drying and/or curing the article at 300-600° F.    
     
     
         52 . The process of  claim 51 , further comprising substantially containing mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         53 . The process of  claim 51 , wherein an air barrier is used to substantially contain mist, spray and fumes of each stage from carrying over to other stages.  
     
     
         54 . The process of  claim 53 , wherein the air barrier comprises a silhouette.  
     
     
         55 . The process of  claim 53 , wherein the air barrier comprises an air knife.  
     
     
         56 . The process of  claim 53 , wherein the air barrier comprises a spray comprising water.  
     
     
         57 . The process of  claim 51 , wherein the acid is sprayed at a flow volume of about 1,000-3,000 gal/minute.  
     
     
         58 . The process of  claim 57 , wherein the flow volume passes through about 10-15 risers having spray nozzles about 10-15 inches apart, and wherein the nozzles are located approximately 6-20 inches from the article.  
     
     
         59 . The process of  claim 51 , wherein the phosphate is sprayed at a flow volume of about 1,000-3,000 gal/minute.  
     
     
         60 . The process of  claim 59 , wherein the flow volume passes through about 10-15 risers having spray nozzles about 10-15 inches apart, and wherein the nozzles are located approximately 6-20 inches from the article.  
     
     
         61 . The process of  claim 51 , wherein the article is at least partially rotated during at least some of the process.