Patent ID: 6648988
Filing Date: 2003-11-18
Classification: B08B,F23J,F27D,F28G

Abstract:
A method of cleaning the surface of an alloy said alloy comprising a base metal and an alloying metal, wherein said alloying metals are selected from the group consisting of chromium, chromium in combination with silicon, chromium in combination with aluminum and chromium in combination with silicon and aluminum, wherein said base metal of said alloy is selected from iron, nickel, cobalt and mixtures thereof, and wherein the alloy has no more than about 20 wt % chromium, comprising the steps of:(a) pigging said alloy surface; and thereafter (b) passivating said alloy surface by contacting said surface with at least one gas selected from the group consisting of steam, a mixture of steam and oxygen, a mixture of steam and air, and a mixture of steam and oxygen and air, such that the mixture has 0-20 wt % free O2 for a time an at a temperature sufficient to form at least one mixed oxide layer on said alloy where n said mixed metal oxide contains an average alloying metal content of from equal to the alloying metal content in said alloy to up to 100% alloying metal.