Stick resistant ceramic coating for cookware
View Patent ↗A method of making a stick resistant cook surface or cooking vessel having the stick resistance in which a hard substrate metal is treated by mechanical buffing/polishing and/or by electropolishing to a high luster surface finish of less than 20 microinches and then coated with a layer of a ceramic nitride, such as zirconium nitride. The electropolishing step is particularly suited for treating non-round shapes or deep drawn cooking vessels having high side walls, such as pots and pans, or square or rectangular shapes which are otherwise difficult to mechanically buff in the interior due to the side wall geometry and/or corners.
1. A method for making a cook surface comprising the steps of:
providing a substrate metal layer selected from the group consisting of stainless steel, carbon steel and titanium wherein said substrate metal layer has a layer of a high heat conductivity metal bonded thereto selected from one of aluminum and copper and defining a clad composite;
mechanical buffing the substrate surface;
electropolishing the substrate surface to form a bright luster finish on said substrate surface, wherein said electropolishing step provides a surface smoothness value Ra on the order of about 50% less than a smoothness value of the substrate after the mechanical buffing step;
cleaning the substrate; and
applying by PVD a coating of zirconium nitride to the bright luster finished substrate surface at a temperature between 500°–900° F. (260°–482° C.), whereby no separation occurs between the layers of the clad composite.
2. The method of claim 1 , wherein the cook surface is used in a cooking device selected from the group consisting of stove-top cookware, oven bakeware, griddle plates and grill surfaces.
3. The method of claim 1 , wherein the cook surface is used in one of a stove-top cookware vessel and an oven bakeware vessel, wherein said vessels having a layer of said zirconium nitride applied on at least an inner cooking or baking surface and on at least selected outer surfaces of said vessels.
4. The method of claim 1 wherein the substrate metal forms an outer layer of a multi-layered metal composite.
5. The method of claim 1 wherein the cook surface is one of a fry pan, saucepan, saucier, casserole, saute pan, stock pot, brazier pan, stir fry pan and omelet pan.
6. The method of claim 1 , wherein the cook surface is an oven baking utensil wherein the stainless steel substrate has a surface finish of 2–4 microinches prior to being coated with said layer of zirconium nitride.
7. The method of claim 1 wherein said stainless steel substrate has a surface finish of less than 1 microinches prior to coating with zirconium nitride.