Catalyst – solid sorbent – or support therefor: product or process – Miscellaneous
Patent
1992-06-25
1994-03-15
Konopka, Paul E.
Catalyst, solid sorbent, or support therefor: product or process
Miscellaneous
148285, B01J 2104, C23C 810
Patent
active
052945863
ABSTRACT:
A method is provided for forming a precursor layer of aluminum oxide on a cold-rolled ferritic stainless steel substrate having an aluminum content of less than five weight percent, and more preferably as low as 1.5 weight percent, by exposing the stainless steel to a hydrogen atmosphere containing controlled quantities of water vapor to provide a controlled hydrogen-to-water vapor ratio of less than about 1400. The aluminum can be provided either as a constituent of the ferritic stainless steel chemistry, or it can be provided as a coating on a ferritic stainless steel which contains essentially no aluminum itself. The resulting oxidation environment is extremely oxygen-poor, having a partial pressure of oxygen between about 2.7.times.10.sup.-23 and 1.9.times.10.sup.-18 atmospheres. In addition, the environment has a relatively high water vapor content of up to about 10,000 ppm. The water vapor serves to replenish the environment's oxygen content, through disassociation of the water vapor, as the oxygen becomes depleted as a result of oxidation of the aluminum in the stainless steel. The above process serves as a pretreatment of the ferritic stainless steel's surface, enabling a subsequent growth of a fully developed layer of aluminum oxide whiskers that provides a surface which promotes adhesion of a catalytically active material to the stainless steel substrate.
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P. Tomaszewicz and G. Wallwork, Oxidation of Metals, vol. 20, Nos. 3/4, 1983, pp. 75-109.
General Motors Corporation
Grove George A.
Konopka Paul E.
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