Method of applying zinc-phosphate conversion crystal coating

Abstract

A modified zinc-phosphate conversion coating method, presented as the Absorbed Solution Layer Phosphating (ASLP) coating method. This modified zinc-phosphate conversion crystal coating (ZPCCC) method is carried out in a reactor, containing metal substrate, a quantity of phosphate solution and a quantity of inert, solid filler particles, the quantity of phosphate solution being dependent on the solid filler particle's solution absorption ability. The ASLP process is carried out in an interface layer between the substrate and the solid filler particles, with the reactor being constructed to provide movement of treated parts and filler particles relative to each other, continually exposing surfaces of the substrate to fresh phosphate solution.

1 . A method for producing and applying a Zinc-Phosphate Conversion Crystal Coating, providing a uniform coating thickness, while utilizing a minimum of phosphating solution, said method comprising:
 treating surfaces of metal substrates with a zinc phosphate solution, causing deposition of a crystalline zinc phosphate coating on said surfaces,   said treating being performed within a reactor volume containing a quantity of relatively small, chemically inert filler particles; and   agitating said filler particles to insure maximization of contact between said filler particles and said surfaces,   said filler particles providing a carrier for said phosphating solution, and enabling minimization of a quantity of said solution required to produce said coating.   
   
   
       2 . The method of  claim 1  wherein said required quantity of said phosphate solution is related to a solution absorption capacity parameter of said filler particles. 
   
   
       3 . The method according to  claim 1 , wherein the size of said filler particles may range between 1-40 mm, and is usually 2-10 mm. 
   
   
       4 . The method of  claim 3 , wherein the shape of said filler is regular. 
   
   
       5 . The method of  claim 3 , wherein the shape of said filler is irregular. 
   
   
       6 . The method of  claim 3 , wherein a mixture of regular and irregular shapes of filler is used. 
   
   
       7 . The method according to  claim 1 , wherein said reactor provides continuous movement of said substrate and said filler particles relative to each other within said reactor volume. 
   
   
       8 . The method according to  claim 1 , wherein said reactor provides periodic movement of said substrate and said filler particles relative to each other within said reactor volume. 
   
   
       9 . The method according to  claim 7 , wherein said movement is performed at a speed, which does not deplete the coating layer. 
   
   
       10 . The method according to  claim 1 , wherein said required quantity of said phosphate solution insures wetting of all surfaces of said filler particles.