Ferrous structural component for use in fouling and corrosive environments, and method of making and using a ferrous structural component

Abstract

A method of using a ferrous structural component is described. The method comprises integrating a ferrous structural component into process equipment, where the ferrous structural component comprises an iron alloy body with a modified surface including an aluminized surface layer that comprises one or more iron aluminides. The modified surface of the iron alloy body is exposed to an oxidative environment, thereby forming, as part of the modified surface, a passivating layer comprising aluminum oxide on the aluminized surface layer. The modified surface is also exposed to a process fluid. The exposure to the oxidative environment occurs prior to and/or upon exposure of the modified surface to the process fluid. Due to protection afforded by the passivating layer, the modified surface resists fouling and corrosion while exposed to the process fluid, as exhibited by a substantial absence of carbonaceous deposits on the iron alloy body.

1 . A ferrous structural component for use in fouling and corrosive environments, the ferrous structural component comprising:
 an iron alloy body having a modified surface comprising:
 an aluminized surface layer comprising one or more iron aluminides; and 
 a passivating layer on the aluminized surface layer, the passivating layer comprising aluminum oxide, 
   wherein, when in direct contact with a process fluid, the modified surface resists fouling and corrosion as exhibited by a substantial absence of carbonaceous deposits on the iron alloy body.   
     
     
         2 . The ferrous structural component of  claim 1 , wherein the modified surface further comprises an interdiffusion layer beneath the aluminized surface layer, the interdiffusion layer comprising a decreasing amount of aluminum and an increasing amount of iron in a depth direction of the iron alloy body. 
     
     
         3 . The ferrous structural component of  claim 2 , wherein the interdiffusion layer comprises a thickness in a range from about 1 micron to about 3 microns,
 wherein the aluminized surface layer has a thickness in a range from about 3 microns to about 30 microns, and   wherein the passivating layer has a thickness in a range from greater than 5 nm to about 40 nm.   
     
     
         4 . The ferrous structural component of  claim 1 , wherein the one or more iron aluminides are selected from the group consisting of Fe 2 Al 5 , FeAl, Fe 3 Al, Fe 5 Al 8 , FeAl 2 , FeAl 3 , and Fe 4 Al 13 . 
     
     
         5 . The ferrous structural component of  claim 1 , wherein the aluminized surface layer comprises a substantially constant amount of aluminum as a function of depth and/or a decreasing amount of aluminum as a function of depth. 
     
     
         6 . The ferrous structural component of  claim 1 , wherein the iron alloy body comprises cast iron or steel. 
     
     
         7 . The ferrous structural component of  claim 1  being a tube, pipeline, expansion fitting, an orifice plate, a blind, a valve, a flange, a connector, a baffle, an agglomerator, a demister, a static mixer, a thermowell, a pitot tube, a sparger, a nozzle, a fractionating column, a component used in a fractionating column, a distillation tray, a downcomer, a heat exchanger, a component used in a heat exchanger, and/or a vessel. 
     
     
         8 . A method of using a ferrous structural component, the method comprising:
 integrating a ferrous structural component into process equipment, the ferrous structural component comprising an iron alloy body with a modified surface including an aluminized surface layer comprising one or more iron aluminides;   exposing the modified surface of the iron alloy body to an oxidative environment, thereby forming, as part of the modified surface, a passivating layer comprising aluminum oxide on the aluminized surface layer; and   exposing the modified surface to a process fluid,   wherein the exposure to the oxidative environment occurs prior to and/or upon exposure of the modified surface to the process fluid, and   wherein, due to protection afforded by the passivating layer, the modified surface resists fouling and corrosion while exposed to the process fluid, as exhibited by a substantial absence of carbonaceous deposits on the iron alloy body.   
     
     
         9 . The method of  claim 8 , wherein the modified surface further comprises an interdiffusion layer beneath the aluminized surface layer, the interdiffusion layer comprising a decreasing amount of aluminum and an increasing amount of iron in a depth direction of the iron alloy body. 
     
     
         10 . The method of  claim 8 , wherein the exposure to the process fluid occurs at an elevated temperature. 
     
     
         11 . The method of  claim 8 , wherein the exposure to the oxidative environment occurs prior to the exposure to the process fluid during an oxidizing heat treatment. 
     
     
         12 . The method of  claim 8 , wherein the process fluid comprises hydrocarbon and/or oxygenate components and/or water. 
     
     
         13 . The method of  claim 12 , wherein the process fluid comprises petroleum, natural gas, oil, one or more petrochemicals, a biofuel, and/or water. 
     
     
         14 . The method of  claim 8 , wherein the ferrous structural component comprises a tube, a pipeline, an expansion fitting, an orifice plate, a blind, a valve, a flange, a connector, a baffle, an agglomerator, a demister, a static mixer, a thermowell, a pitot tube, a sparger, a nozzle, a fractionating column, a component used in a fractionating column, a distillation tray, a downcomer, a heat exchanger, a component used in a heat exchanger, and/or a vessel. 
     
     
         15 . The method of  claim 8 , wherein the passivating layer is reformable if damaged or removed. 
     
     
         16 . A method of imparting fouling- and corrosion-resistance to a ferrous structural component, the method comprising:
 introducing aluminum into a surface of an iron alloy body at an elevated temperature to form a modified surface of the iron alloy body, the modified surface including an aluminized surface layer comprising one or more iron aluminides;   exposing the iron alloy body comprising the modified surface to an oxidizing environment, thereby forming, as part of the modified surface, a passivating layer comprising aluminum oxide on the aluminized surface.   
     
     
         17 . The method of  claim 16 , wherein the modified surface further comprises an interdiffusion layer beneath the aluminized surface layer, the interdiffusion layer comprising a decreasing amount of aluminum and an increasing amount of iron in a depth direction of the iron alloy body. 
     
     
         18 . The method of  claim 16 , wherein the exposure to the oxidizing environment occurs upon exposure of the modified surface to a process fluid while the ferrous structural component is in use. 
     
     
         19 . The method of  claim 16 , wherein the exposure to the oxidizing environment occurs during an oxidizing heat treatment prior to use of the ferrous structural component. 
     
     
         20 . The method of  claim 16 , wherein the aluminum is introduced into the surface of the iron alloy body via pack aluminization using a pack comprising an aluminum source, a halide salt, and aluminum oxide.