Method for applying manganese phosphate layers

Abstract

The invention relates to a method for applying manganese phosphate layers to iron or steel surfaces using phosphating solutions containing manganese, phosphate, iron (II) ions as well as nitroguinidine, as well as its application to workpieces that are subject to sliding friction.

1 - 7 . (Canceled).  
     
     
         8 . A method for applying manganese phosphate layers to iron or steel surfaces comprising contacting workpieces with a phosphating solution comprising 
 0.2 to 4 g/l of iron (II) ions    10 to 25 g/l of manganese ions    25 to 50 g/l of phosphate ions (calc. as P 2 O 5 )    3 to 35 g/l of nitrate ions    0.5 to 5 g/l of nitroguanidine    said solution having 7 to 24 points of free acid, 50 to 140 points of total acid, and an S value of 0.2 to 1, and drying the workpieces to form a manganese phosphate layer having a minimum thickness of 2 μm and an average maximum roughness depth (R z ) of from 1.3 to 2.5 μm.    
     
     
         9 . The method according to  claim 8 , wherein said phosphating solution that comprises 0.5 to 2 g/l of nitroguanidine.  
     
     
         10 . A method according to  claim 8 , wherein the phosphating solution comprises not more than 2.5 g/l of iron (II) ions.  
     
     
         11 . A method according to  claim 8 , wherein the workpiece is steel and said phosphating solution comprises a complex-forming agent for the alloying constituents of the steel.  
     
     
         12 . A method according to  claim 11 , wherein said coupler-forming agent is citric acid.  
     
     
         13 . A method according to  claim 8 , wherein said phosphating solution further comprises at least one metal ion selected from the group consisting of 
 0.2 to 4 g/l of nickel ions and    0.2 to 4 g/l of magnesium ions.    
     
     
         14 . A method according to  claim 8 , wherein at least a portion of the manganese ions in said phosphating solution are replaced by manganese carbonate to neutralize free acid.  
     
     
         15 . A the method according to  claim 8 , wherein said workpieces are subjected to a sliding friction.  
     
     
         16 . A method according to  claim 8 , wherein said workpieces are selected from the group consisting of axles, gear mechanism parts and engine pistons.