Reduction of the loss of zinc by its reaction with oxygen in galvanized steel and batteries

Abstract

A non-porous Zn 2+ conducting inorganic lamellar layer is formed on the zinc coating of galvanized steel or on a zinc anode of an electrochemical cell. The layer reduces the rate of the unwanted chemical reaction of zinc and oxygen but allows desired electrochemical reactions underlying the cathodic protection of the steel and the efficient utilization of zinc anodes in electrochemical cells, e.g., a physiological buffer solution or serum as their electrolytes. The ion conducting non-porous lamellar layer having a hopeite phase Zn 3 (PO 4 ) 2 .4H 2 O may be formed spontaneously on, e.g., NAFION® coated zinc anodes discharged in neutral pH saline phosphate solutions.

1 . A composition comprising: 
 a phosphate anion and one or more metal cations that form a non-porous inorganic lamellar layer on a substrate surface, wherein the lamellar layer allows the transport of at least one ion at 25° C.    
   
   
       2 . The composition of  claim 1 , wherein the non-porous lamellar layer comprises hopeite.  
   
   
       3 . The composition of  claim 1 , wherein the non-porous lamellar layer is substantially oxygen impermeable.  
   
   
       4 . The composition of  claim 1 , wherein the non-porous lamellar layer conducts Zn 2+  ions.  
   
   
       5 . The composition of  claim 1 , wherein the non-porous lamellae layer further comprises nickel, magnesium, manganese, calcium, cobalt, copper, magnesium or mixtures and combinations thereof.  
   
   
       6 . A substrate comprising: 
 a first inner metal and a second outer metal, the surface of the second outer metal reacted to form a non-porous lamellar layer that comprises a compound formed of a phosphate anion and one or more metal cations, the lamellar layer allowing the transport of at least one ion at 25° C.    
   
   
       7 . The composition of  claim 6 , wherein the non-porous lamellar layer is substantially oxygen impermeable.  
   
   
       8 . The composition of  claim 6 , where the first inner metal is an alloy of iron or copper.  
   
   
       9 . The composition of  claim 8 , where the alloy of iron is steel.  
   
   
       10 . The composition of  claim 6 , where the second outer metal is zinc of galvanized steel.  
   
   
       11 . A method of surface treating a corrodible metal comprising the steps of: 
 coating a corrodible metal with a non-porous lamellar film comprising an inorganic phosphate of one or more metal cations to form a substantially impermeable film that provides an anticorrosion effect on the corrodible metal.    
   
   
       12 . The method of  claim 11 , wherein the non-porous lamellar film comprises hopeite.  
   
   
       13 . An electrical power generating electrochemical cell comprising: 
 an electrolyte providing for ion transport between a cathode and a zinc anode, wherein the zinc anode comprises a non-porous inorganic lamellar film of a compound of phosphate and one or more metal cations, the film preventing or reducing non-Faradaic corrosion of the zinc anode.    
   
   
       14 . The cell of  claim 13 , wherein the lamellar film prevents, or reduces the rate of, the reaction of oxygen of with the zinc of the zinc anode.  
   
   
       15 . The cell of  claim 13 , wherein the substantially non-porous lamellar film is hopeite.  
   
   
       16 . The cell of  claim 13 , wherein the substantially non-porous lamellar film conducts Zn2+ ions.  
   
   
       17 . The cell of  claim 13 , wherein the electrolyte comprises a body fluid.  
   
   
       18 . The cell of  claim 13 , wherein the cathode and the zinc anode are implanted in an animal.  
   
   
       19 . A zinc anode electrode protected against non-Faradaic corrosion by an ion conducting inorganic lamellar layer that is formed by passing a current through the electrode immersed in a phosphate containing solution to form a non-porous hopeite lamellar layer on the zinc electrode.  
   
   
       20 . The electrode of  claim 19 , wherein the lamellar layer comprises hopeite.  
   
   
       21 . A composition comprising: 
 a cation exchanger coated on a metal substrate; and    an inorganic lamellar layer formed on or in the cation exchanger that is substantially oxygen impermeable and that allows the transport of one or more metal ions, wherein the inorganic lamellar layer comprises one or more phosphate anions and one or more metal cations, whereby the cation exchanger influences relative growth of the inorganic lamellar layer.    
   
   
       22 . The composition of  claim 21 , wherein the lamellar layer comprises hopeite and the metal substrate comprises zinc.  
   
   
       23 . A method of surface treating a corrodible metal comprising the steps of: 
 coating a corrodible metal with a cation exchanger;    forming an inorganic lamellar layer on or in the cation exchanger that allows the transport of one or more metal ions and that provides an anticorrosion effect on the corrodible metal, wherein the inorganic lamellar layer comprises one or more phosphate anions and one or more metal cations, whereby the cation exchanger influences relative growth of the inorganic lamellar layer.    
   
   
       24 . The method of  claim 23 , wherein the lamellar film comprises hopeite and the corrodible metal comprises zinc.  
   
   
       25 . A method of forming a metal electrode that is protected against non-Faradaic corrosion comprising the steps of: 
 immersing a cation exchanger coated metal electrode in a phosphate containing solution; and    forming an inorganic lamellar layer on or in the cation exchanger that allows the transport of one or more metal ions, whereby the cation exchanger influences relative growth of the inorganic lamellar layer.    
   
   
       26 . The method of  claim 25 , wherein the non-porous lamellar film comprises hopeite and the cation exchanger coated metal electrode comprises zinc.