Micro-Arc Assisted Electroless Plating Methods

Abstract

A method for electorless plating of a substrate such as magnesium, aluminium, titanium or an alloy, comprises the steps of forming a very thin film of oxide on the substrate by plasma electrolytic oxidation before depositing a layer comprising nickel on the substrate by electroless nickel deposition.

1 . A method for electroless plating of a substrate comprising the steps of: forming a layer of oxide on the substrate by plasma electrolytic oxidation (PEO), and depositing a layer comprising nickel on the substrate by electroless nickel (EN) deposition. 
   
   
       2 . A method according to  claim 1  wherein the substrate is selected from magnesium, aluminium, titanium and their alloys, and iron alloys. 
   
   
       3 . A method according to  claim 1  wherein the substrate consists essentially of magnesium, a magnesium alloy, aluminium, an aluminium alloy, titanium, or a titanium alloy. 
   
   
       4 . A method according to  claim 1  wherein the substrate is magnesium or a magnesium alloy. 
   
   
       5 . A method according to  claim 1  wherein the substrate is copper or a copper alloy. 
   
   
       6 . A method according to  claim 1  comprising carrying out PEO to a voltage between electrodes up to about 450 Volts. 
   
   
       7 . A method according to  claim 1  comprising carrying out PEO for a time of at least two minutes. 
   
   
       8 . A method according to  claim 1  comprising carrying out PEO for a time of up to 10 minutes. 
   
   
       9 . A method according to  claim 1  comprising carrying out PEO with a current density of up to about 1000 A/m −2 . 
   
   
       10 . A method according to  claim 1  comprising carrying out PEO at an electrolyte temperature at or below about 45° C. 
   
   
       11 . A method according to  claim 1  comprising carrying out PEO at an concentration of major electrolyte constituents of up to 5 g/litre. 
   
   
       12 . A method according to  claim 1  comprising carrying out PEO in an electrolyte which includes phosphate ions. 
   
   
       13 . A method according to  claim 1  comprising carrying out PEO to form said layer of oxide as a very thin film of oxide on the substrate. 
   
   
       14 . A method according to  claim 1  wherein depositing a layer which includes nickel on the substrate by EN deposition comprises depositing a layer of substantially pure nickel metal on the substrate. 
   
   
       15 . A method according to  claim 1  comprising carrying out EN deposition in an electrolyte which includes nickel sulphate as a nickel source. 
   
   
       16 . A method according to  claim 1  comprising carrying out EN deposition in an electrolyte which includes nickel carbonate as a nickel source. 
   
   
       17 . A method according to  claim 1  comprising depositing a layer comprising nickel deposition by EN at an electrolyte pH of between about 4.5 and about 8. 
   
   
       18 . A method according to  claim 1  comprising depositing a layer comprising nickel deposition by EN at an electrolyte pH of between about 6 and about 8. 
   
   
       19 . A method according to  claim 1  comprising depositing a layer comprising nickel by EN deposition at an electrolyte temperature of about 80° C. 
   
   
       20 . A method according to  claim 1  also including chemically depositing metal onto the substrate between the PEO and the EN deposition. 
   
   
       21 .- 23 . (canceled) 
   
   
       24 . A method for electroless plating of a substrate which consists essentially of magnesium, a magnesium alloy, aluminium, and aluminium alloy, titanium or a titanium alloy, comprising the steps of forming a very thin film of oxide on the substrate by plasma electrolytic oxidation (PEO), and depositing a layer comprising nickel on the substrate by electroless nickel (EN) deposition in an electrolyte which includes nickel sulphate or nickel carbonate as a nickel source. 
   
   
       25 .- 28 . (canceled)