Electrolytic passivated tin plated steel

Abstract

An electrolyte composition for passifying tin plated steel wherein the essential ingredient consists of a mixture of organic hydroxyl acids and phenol organic acids; a method of passifying tin plate steel articles with the composition by electrolysis with a pH of about 7.0-10.0 and preferably a pH of 8.0-9.5; and providing the passified tin plated steel article produces by the method along with the passified articles having an appropriate paint thereon.

1 . A tin plated steel passificating composition wherein the essential ingredient consists of a mixture of organic hydroxyl acids and phenol organic acids. 
   
   
       2 . The composition of  claim 1  wherein the organic hydroxyl acid is selected from C 2 -C 6 hydroxyl acids. 
   
   
       3 . The composition of  claim 2  wherein the C 2 -C 6 hydroxyl acids are selected from the group consisting of hydroxyl acetic acid, D-gluconic acid, citric acid and lactic acid; and the phenol organic acids are selected from the group consisting of hydrolysable tannic acid, gallic acid and dihydroxy benzoic acid. 
   
   
       4 . The composition of  claim 3  wherein the composition is an electrolyte composition having a pH of 7.0 to 10.0 and preferably a pH of 8.0-9.5. 
   
   
       5 . The composition of  claim 4  wherein the composition contains less than 4.0 % of a compound or mixture of compounds selected from the group consisting of phosphates, silicates and aromatic acid salts. 
   
   
       6 . The composition of  claim 5  wherein the phosphate is phosphoric acid or its salt, the silicate is potassium silicate and the aromatic acid is potassium salt of 1,3,4 benzenetricarboxylic acid. 
   
   
       7 . A passified tin plated article which has been passified by a composition wherein the essential ingredient of the composition is selected from a mixture consisting of mixture of organic hydroxyl acids and phenol organic acids. 
   
   
       8 . The passified tin plated article  claim 6  wherein the organic hydroxyl acid is selected from C 2 -C 6 hydroxyl acids. 
   
   
       9 . The passified tin plated article  claim 6  wherein the C 2 -C 6 hydroxyl acids are selected from the group consisting of hydroxyl acetic acid, D-gluconic acid, citric acid and lactic acid;
 and the phenol organic acids are selected from the group consisting of hydrolysable tannic acid, gallic acid and dihydroxy benzoic acid.   
   
   
       10 . The passified tin plated article  claim 7  wherein the composition is an electrolyte composition having a pH of 7.0-10.0 and preferably a pH of 8.0-9.5. 
   
   
       11 . The passified tin plated article  claim 10  wherein the composition contains less than 4.0 % of a compound or mixture of compounds selected from the group consisting of phosphates, silicates and aromatic acid salts. 
   
   
       12 . The passified tin plated article of  claim 11  wherein the phosphate is phosphoric acid or its salt, the silicate is potassium silicate and the aromatic acid is potassium salt of 1,3,4 benzenetricarboxylic acid. 
   
   
       13 . The passified tin plated steel article of  claim 10 , wherein the article has a layer of an appropriate paint to provide a paint protected zinc, zinc plated, or steel article that passes the ASTM-D3359 paint adhesion test. 
   
   
       14 . A method of preparing a passified tin plated steel article comprising electrolytically passifating a cleaned tin plated steel article with an electrolyte composition wherein the essential ingredient consists of a mixture of organic hydroxyl acids and phenol organic acids. 
   
   
       15 . The method of  claim 10  wherein the organic hydroxyl acid is selected from C 2 -C 6 hydroxyl acids. 
   
   
       16 . The method of  claim 11  wherein the C 2 -C 6  hydroxyl acids are selected from the group consisting of hydroxyl acetic acid, D-gluconic acid, citric acid and lactic acid; and the phenol organic acids are selected from the group consisting of hydrolysable tannic acid, gallic acid and dihydroxy benzoic acid. 
   
   
       17 . The method of  claim 12  wherein the electrolyte composition having a pH of 7.0-10.0 and preferably a pH of 8.0-9.5. 
   
   
       18 . The method of  claim 17  wherein the composition contains less than 4.0% of a compound or mixture of compounds selected from the group consisting of phosphates, silicates and aromatic acid salts. 
   
   
       19 . The method of  claim 18  wherein the phosphate is phosphoric acid or its salt, the silicate is potassium silicate and the aromatic acid is potassium salt of 1,3,4 benzenetricarboxylic acid. 
   
   
       20 . The method of  claim 17 , comprising the further steps of drying the passified tin plated steel article, and painting the dried article to provide paint protected tin plated steel article that will pass the ASTM-D3359 paint adhesion test.