Electrolyte composition and method of use thereof

Abstract

Provided herein is an electrolyte composition including a metal silicate or a metal aluminate, a metal phosphate, zinc oxide particles, and a complexing agent useful for plasma electrolytic oxidation treatment of a surface of a metal substrate.

What is claimed is: 
     
         1 . An electrolyte composition comprising a metal silicate or a metal aluminate, a metal phosphate, zinc oxide particles, and a complexing agent. 
     
     
         2 . The electrolyte composition of  claim 1  further comprising an aqueous solvent. 
     
     
         3 . The electrolyte composition of  claim 1 , wherein the metal silicate or metal aluminate is sodium silicate, calcium silicate, tricalcium silicate, tricalcium aluminate, tricalcium iron aluminate, potassium silicate, or a mixture thereof. 
     
     
         4 . The electrolyte composition of  claim 1 , wherein the metal phosphate is selected from the group consisting of sodium hexametaphsophate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium polyphosphate, trisodium phosphate, and sodium pyrophosphate. 
     
     
         5 . The electrolyte composition of  claim 1 , wherein the zinc oxide particles are micron-sized zinc oxide, nano-sized zinc oxide particles, or a mixture thereof. 
     
     
         6 . The electrolyte composition of  claim 1 , wherein the complexing agent is ethylene diamine tetraacetic acid (EDTA), triethanolamine, sodium tartrate, citrate, oxalate, or a mixture thereof. 
     
     
         7 . The electrolyte composition of  claim 1 , wherein the metal phosphate is selected from the group consisting of sodium hexametaphsophate, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium polyphosphate, trisodium phosphate, and sodium pyrophosphate; the zinc oxide is micron zinc oxide, nano zinc oxide, or a mixture thereof; and the complexing agent is EDTA, triethanolamine, sodium tartrate, citrate, oxalate, or a mixture thereof. 
     
     
         8 . The electrolyte composition of  claim 1 , wherein the metal silicate or the metal aluminate is sodium silicate, the metal phosphate is sodium hexametaphosphate, and the complexing agent is disodium EDTA. 
     
     
         9 . The electrolyte composition of  claim 2 , wherein the metal silicate or metal aluminate, the metal phosphate, the zinc oxide particles, and the complexing agent are present in the aqueous solution at a concentration of about 5 to about 50 g/L, about 1 to about 30 g/L, about 2 to about 25 g/L, and about 1 to about 20 g/L, respectively. 
     
     
         10 . The electrolyte composition of  claim 9 , wherein the metal silicate or the metal aluminate is sodium silicate, the metal phosphate is sodium hexametaphosphate, and the complexing agent is disodium EDTA. 
     
     
         11 . The electrolyte composition of  claim 2 , wherein the aqueous solvent has a pH of about 6 to about 12. 
     
     
         12 . The electrolyte composition of  claim 2 , wherein the metal silicate or the metal aluminate is sodium silicate, the metal phosphate is sodium hexametaphosphate, and the complexing agent is disodium EDTA; and the sodium silicate, sodium hexametaphosphate, zinc oxide particles, and the disodium EDTA are present in the aqueous solvent at a concentration of about 10 to about 20 g/L, about 10 to about 20 g/L, about 5 to about 15 g/L, and about 10 to about 20 g/L, respectively. 
     
     
         13 . The electrolyte composition of  claim 2 , wherein the metal silicate or the metal aluminate is sodium silicate, the metal phosphate is sodium hexametaphosphate, and the complexing agent is disodium EDTA; the sodium silicate, sodium hexametaphosphate, zinc oxide particles, and the disodium EDTA are present in the aqueous solvent at a concentration of about 15 g/L, about 15 g/L, about 10 g/L, and about 15 g/L, respectively; and the aqueous solvent has a pH of about 6 to about 12. 
     
     
         14 . A method of plasma electrolytic oxidation (PEO) treatment of a surface of a metal substrate, the method comprising:
 providing an anode comprising the metal substrate;   an anode; and   an electrolyte solution comprising the electrolyte composition of  claim 1 , wherein the electrolyte solution is in contact with the cathode and the anode; and   applying an electric current between the cathode and the anode resulting in the PEO of at least a portion of the surface of the metal substrate.   
     
     
         15 . The method of  claim 14 , wherein the metal substrate is aluminum or an alloy thereof. 
     
     
         16 . The method of  claim 14 , wherein the step of applying the electric current comprises applying a constant current using at about 5 to about 20 amps/dm 2  and frequency of about 50 to about 3,000 Hz or a constant voltage of about 300 to about 800 volts at a frequency of about 50 to about 3,000 Hz. 
     
     
         17 . The method of  claim 14 , wherein the step of applying the electric current comprises applying a constant current using about 20 amps/dm 2  and frequency of about 100 Hz. 
     
     
         18 . The method of  claim 14 , wherein the electrolyte solution comprises the metal silicate or metal aluminate, the metal phosphate, the zinc oxide particles, and the complexing agent are present in the aqueous solution at a concentration of about 5 to about 50 g/L, about 1 to about 30 g/L, about 2 to about 25 g/L, and about 1 to about 20 g/L, respectively. 
     
     
         19 . The method of  claim 17 , wherein the electrolyte solution comprises the metal silicate or the metal aluminate is sodium silicate, the metal phosphate is sodium hexametaphosphate, and the complexing agent is disodium EDTA; the sodium silicate, sodium hexametaphosphate, zinc oxide particles, and the disodium EDTA are present in the aqueous solvent at a concentration of about 15 g/L, about 15 g/L, about 10 g/L, and about 15 g/L, respectively; and the aqueous solvent has a pH of about 6 to about 12. 
     
     
         20 . The method of  claim 15 , wherein the electrolyte solution comprises the metal silicate or the metal aluminate is sodium silicate, the metal phosphate is sodium hexametaphosphate, and the complexing agent is disodium EDTA; the sodium silicate, sodium hexametaphosphate, zinc oxide particles, and the disodium EDTA are present in the aqueous solvent at a concentration of about 15 g/L, about 15 g/L, about 10 g/L, and about 15 g/L, respectively; and the aqueous solvent has a pH of about 6 to about 12; and the step of applying the electric current comprises applying a constant current using about 20 amps/dm 2  and frequency of about 100 Hz.