Coating Compositions, Applications Thereof, and Methods of Forming

Abstract

A method for forming protective corrosive resistant coatings on equipment is disclosed. The coating is formed from a NiCrMo alloy composition containing at least two gettering components selected from Al, Si, and Ti in an amount of up to 25 wt. %. The coating in one embodiment is applied using a thermal spray technique, e.g., twin wire arc spray, forming coatings of 5-50 mils thickness having a fine-scale micro-pore structure which is effectively non-permeable in aggressive solutions, and resist selective oxidation in thermal spraying of components for maximized corrosion performance The coating is further characterized as having excellent adhesion strength even when applied with varying parameters as in manual on-site coating applications.

1 . A method for forming a protective coating on an equipment for use in a corrosive environment, the method comprising:
 preparing a substrate on the equipment to be coated;   applying a coating layer comprising a NiCrMoX alloy onto the substrate to be coated, X contains at least two gettering elements selected from Al, Si, Ti in an amount of 5-20 wt. %;   wherein the coating layer formed by the alloy has an impurity content of less than 15%, a corrosion rate of less than 150 mpy measured according to ASTM G31, and an adhesion strength of at least 9,000 psi measured according to ASTM D4541.   
     
     
         2 . The method of  claim 1 , wherein the coating layer formed has an impurity content of less than 10%. 
     
     
         3 . The method of  claim 1 , wherein the coating layer formed has an adhesion strength of at least 10,000 psi measured according to ASTM D4541. 
     
     
         4 . The method of  claim 1 , wherein the coating layer formed has a corrosion rate of less than 125 mpy measured according to ASTM G31. 
     
     
         5 . The method of  claim 1 , wherein the coating layer formed has a corrosion rate of less than 100 mpy measured according to ASTM G31. 
     
     
         6 . The method of  claim 1 , wherein the substrate to be coated is any of an iron, nickel, cobalt or copper based alloy. 
     
     
         7 . The method of  claim 1 , wherein the substrate to be coated is prepared by giving an anchor profile abrasive blast of at least 0.5 mils. 
     
     
         8 . The method of  claim 7 , wherein the substrate to be coated is prepared by giving an anchor profile abrasive blast of 0.5-6 mils. 
     
     
         9 . The method of  claim 1 , wherein the coating layer has a thickness of 2-100 mils. 
     
     
         10 . The method of  claim 1 , wherein the coating layer is applied using thermal spray coating employing any of sprayed flame, wire, plasma, and high velocity oxy fuel (HVOF). 
     
     
         11 . The method of  claim 9 , wherein the thermal sprayed coating layer is applied using twin wire arc spray (TWAS). 
     
     
         12 . The method of  claim 9 , wherein the thermal sprayed coating layer is applied manually with at least one of: a spray angle variation of +60° from 90°; a traverse rate variation of ±600 inches/min; and a spray distance variation of up to 9″. 
     
     
         13 . The method of  claim 9 , wherein the thermal sprayed coating layer formed has an adhesion strength variation of less than 25% when sprayed with a spray angle variation of +60° from 90°. 
     
     
         14 . The method of  claim 9 , wherein the thermal sprayed coating layer formed has an adhesion strength variation of less than 25% when sprayed with a traverse rate variation of ±600 inches/min. 
     
     
         15 . The method of  claim 9 , wherein the thermal sprayed coating layer formed has an adhesion strength variation of less than 25% when sprayed with a distance variation of up to 9″. 
     
     
         16 . The method of  claim 9 , wherein the coating layer is applied using thermal spray coating employing a cored wire formed with a sheet having an alloy composition of NiCr rolled into a tubular form, containing X as a powder contained within the tubular form as a core, wherein X contains Al and Mo and at least one of two gettering elements Si and Ti. 
     
     
         17 . The method of  claim 16 , wherein the coating layer has at least 10% less gettering elements X present in metal and metal oxide form as compared to original concentration of X in the cored wire. 
     
     
         18 . The method of  claim 16 , wherein the coating layer has at least 20% less aluminum present in metal and metal oxide form as compared to original concentration of aluminum in the cored wire. 
     
     
         19 . The method of  claim 1 , wherein the NiCrMoX alloy composition has in weight %: 12-25% Cr; 8-15% Mo; at least two gettering elements selected from Al, Si, and Ti in an amount of up to 12% each with a total concentration of 5-25%; balance of Ni and unavoidable impurities. 
     
     
         20 . The method of  claim 19 , wherein the two gettering elements selected from Al, Si, and Ti are in an amount of up to 10% each with a total concentration between 10-20%. 
     
     
         21 . The method of  claim 1 , wherein applying a coating layer comprising a NiCrMoX alloy comprises
 thermal spraying a cored wire formed with a sheet having an alloy composition of NiCr rolled into a tubular form rolled into a tubular form containing X as a powder contained within the tubular form as the core,   wherein X contains Mo, and Al and Si as gettering elements, and   wherein the gettering elements have at least a 30% decrease in deposition efficiency for Al and at least a 20% decrease in deposition efficiency for Si.   
     
     
         22 . The method of  claim 21 , wherein the coating layer has at least 10% less gettering elements X present in metal and metal oxide form as compared to original concentration of X in the cored wire. 
     
     
         23 . A method for forming a protective coating on an equipment for use in a corrosive environment, the method comprising:
 preparing a substrate on the equipment to be coated;   applying onto a substrate a coating layer using thermal spray coating with a wire feedstock comprising a nickel alloy composition containing in weight %: Cr: 12%-25%; Mo: 8%-15%; and at least two gettering elements selected from Al: 0.25-12%, Si: up to 10%, and Ti: up to 5%; balance of Ni and unavoidable impurities;   wherein the coating layer formed by the nickel alloy composition has an impurity content of less than 15% , a corrosion rate of less than 150 mpy measured according to ASTM G31, and an adhesion strength of at least 9,000 psi measured according to ASTM D4541.   
     
     
         24 . The method of  claim 23 , wherein the coating layer formed has an impurity content of less than 10%, a corrosion rate of less than 100 mpy measured according to ASTM G31 and an adhesion strength of at least 10,000 psi measured according to ASTM D4541. 
     
     
         25 . A method for forming a protective coating on an equipment for use in a corrosive environment, the method comprising:
 applying onto at least a surface on the equipment a coating layer using thermal spray coating with a wire feedstock having components of NiCrMoX, wherein the Ni—Cr components form an alloy sheath rolled into a tubular form, wherein the X component contains Mo, Al and at least one of two gettering elements Si and Ti and forms a powder contained within the tubular form as the core, wherein the powder is in an amount of 5-20 wt. % based on total weight of the wire feedstock;   wherein at least 10% of the gettering elements form hard oxide particles which do not adhere to the surface of the equipment and function to grit blast the surface for the coating layer formed to have an adhesion strength of at least 9,000 psi measured according to ASTM D4541.   
     
     
         26 . The method of  claim 25 , wherein the coating layer formed has an impurity content of less than 15% and a corrosion rate of less than 150 mpy measured according to ASTM G31. 
     
     
         27 . The method of  claim 25 , wherein the method is for repairing the equipment by forming the protective coating. 
     
     
         28 . The method of  claim 25 , wherein the method is for periodic coating of equipment selected from the group of recovery boilers, furnace tubes, metal sheets, panels, pressure vessels, separator vessels, drums, rail cars, heat exchangers, pipes, heat exchanger parts, storage tanks, valves, chamber enclosure wall, substrate support, gas delivery system and components, and gas exhaust system and components. 
     
     
         29 . The method of  claim 25 , wherein the method is for coating an overlay on the equipment.