Metal protection

Abstract

Metals for use in glass-making furnaces and which are susceptible to oxidation at furnace operating temperatures, especially iridium or molybdenum, are protected by applying at least (200) microns thickness of a coating formed of metal oxide particles in a metal oxide matrix. Oxidation, measured by weight loss, is significantly reduced.

1 . A protected metal, having a metal substrate selected from the group consisting of platinum group metals, molybdenum, rhenium, niobium, tungsten and alloys of any of such metals, comprising, on a surface exposed to an oxygen-containing atmosphere, a continuous composite coating of at least 200 microns thickness, which coating comprises metal oxide particles in a metal oxide matrix. 
   
   
       2 . A protected metal according to  claim 1 , wherein the metal substrate is iridium or an alloy thereof. 
   
   
       3 . A protected metal according to  claim 1 , wherein the metal substrate is platinum or an alloy thereof. 
   
   
       4 . A protected metal according to  claim 1 , wherein the metal substrate is molybdenum, rhenium, niobium, tungsten or an alloy thereof. 
   
   
       5 . A protected metal according to  claim 1 , wherein the metal oxide matrix is derived from a silicate salt. 
   
   
       6 . A protected metal according to  claim 1 , wherein the metal oxide particles comprise from 45 to 90% by wt Al 2 O 3 , 10 to 45% by wt of SiO 2 , and less than 1% by wt of Fe 2 O 3  and other metal oxides, from a total composition of 100%. 
   
   
       7 . A protected metal according to  claim 1 , wherein the coating has been formed from two or more layers of coating. 
   
   
       8 . A method of protecting a metal substrate selected from the group consisting of platinum group metals, molybdenum, rhenium, niobium, tungsten and alloys of any of such metals surface from oxidation in an oxygen-containing atmosphere at elevated temperature, comprising applying to said metal substrate a coating of metal oxide particles together with a metal oxide matrix or a metal oxide matrix precursor. 
   
   
       9 . A method according to  claim 8 , comprising the application of two or three layers of the coating. 
   
   
       10 . A method of making glass comprising using a protected metal according to  claim 1 . 
   
   
       11 . A protected metal according to  claim 1 , wherein the continuous composite coating is between 500 and 1000 microns in thickness.