Method of coating an iron-based article
View Patent ↗A method of coating an iron-based article includes a first heating step of heating a substrate that includes an iron-based material in the presence of an aluminum source material and halide diffusion activator. The heating is conducted in a substantially non-oxidizing environment, to cause the formation of an aluminum-rich layer in the iron-based material. In a second heating step, the substrate that has the aluminum-rich layer is heated in an oxidizing environment to oxidize the aluminum in the aluminum-rich layer.
1. A method of coating an iron-based article, the method comprising:
in a first heating step, heating a substrate including an iron-based material in the presence of an aluminum source material and a halide diffusion activator, in a substantially non-oxidizing environment, to cause formation of an aluminum-rich layer on at least a portion of the iron-based material; and
in a second heating step, heating the substrate that has the aluminum-rich layer in an oxidizing environment to oxidize the aluminum in the aluminum-rich layer,
wherein the first heating step includes heating at a heating temperature such that a ratio of the melting temperature of the iron-based material to the heating temperature is 1.5-2.1 and, after the second heating step, cooling the substrate at a rate of equal to or less than 10° C. per minute, and wherein the iron-based material is stainless steel.
2. The method as recited in claim 1 , wherein the first heating step includes heating at a heating temperature such that a ratio of the melting temperature of the iron-based material to the heating temperature is 1.6-1.9.
3. The method as recited in claim 1 , wherein the second heating step is conducted at a heating temperature of 800°-1000° C.
4. The method as recited in claim 1 , wherein the cooling rate of is 1°-2° C. per minute.
5. The method as recited in claim 1 , wherein the first heating step is conducted at a temperature of 750°-850° C.
6. The method as recited in claim 1 , wherein the first heating step is conducted at a temperature of 800°-825° C.
7. The method as recited in claim 1 , wherein the heating of the first heating step is conducted at a pressure of 14.7-19.7 psia.
8. The method as recited in claim 1 , wherein the substantially non-oxidizing environment includes hydrogen in an amount of up to 4 vol %.
9. The method as recited in claim 1 , wherein the substrate is at least partially enclosed in a titanium-containing enclosure.
10. The method as recited in claim 1 , wherein the substrate is at least partially enclosed in a tantalum-containing enclosure.
11. The method as recited in claim 1 , further comprising providing the aluminum source material and the halide diffusion activator in a slurry, and applying the slurry on the iron-based material.
12. The method as recited in claim 1 , further comprising, after the second heating step, abrading the substrate to remove any excess of the aluminum source material and the halide diffusion activator.
13. The method as recited in claim 1 , wherein the aluminum source material includes cobalt.
14. The method as recited in claim 1 , wherein the aluminum source material is Co 2 Al 5 .
15. The method as recited in claim 1 , wherein the aluminum source material consists of aluminum and cobalt.
16. The method as recited in claim 1 , wherein the substrate is a metallic component of an electrochemical device, the metallic component being located laterally outside of an electron or ion flow area FA of the electrochemical device.