Microcrystalline anodic coatings and related methods therefor
Methods of preparing metal and metal alloys with partially microcrystalline anodic coatings are disclosed. Associated article therefrom are correspondingly disclosed. The partially microcrystalline anodic coatings exhibit steam, superheated steam, alkaline and acidic resistance. Partially microcrystalline anodic coating can be prepared by impregnation of micropores of a metal or metal substrate with metal precursor species, conversion of the metal precursor species into metal hydroxides, thermal treatment to dry out moisture and to promote phase transformation of the metal hydroxide product into metal oxides solids and bonding with metastable metal oxide substance in the pore structure of the metal or metal alloy substrate, and hydrothermal sealing to create sealed partially microcrystalline anodic coating.
1. An aluminum article comprising an anodized coating with a thickness of at least about 0.05 mm and having an X-ray diffraction (XRD) spectrum with partially microcrystalline aluminum hydroxide peaks at about 18°, 37°, 44°, and 62°.
2. The aluminum article of claim 1 , wherein the anodized coating has a Taber abrasion loss of less than about 109 mg as determined in accordance with ASTM 4060 after immersion in a sodium hydroxide solution at least about 0.04 wt % for 11 days at a temperature in a range of from about 15° C. to about 25° C.
3. The aluminum article of claim 1 , wherein the anodized coating is dyed and has a fading of less than a ΔL* of about 1.5, a Δa* of about 2.0, and a Δb* of about 2.5 values in accordance with a CIE (Commission Internationale d'Eclairage) 1976 L*, a*, b* color scale as performed in accordance with ASTM E 308, after exposure, for at least 5 cycles, to ultrasonic cleaning with a solution having a pH of 12 and to autoclaving at 275° F.
4. The aluminum article of claim 1 , wherein the anodized coating has a thickness in a range of from about 0.051 mm to about 0.061 mm.
5. The aluminum article of claim 4 , wherein the anodized coating is dyed.
6. The aluminum article of claim 4 , wherein the anodized coating does not exhibit a failure mode for at least three test cycles, wherein each test cycle comprises immersing the aluminum article for 24 hours in a 0.04% solution of sodium hydroxide and water having a pH of 11.6 to 12.3.
7. The aluminum article of claim 1 , wherein the partial microcrystalline aluminum hydroxide has a structure that exhibits a repeating pattern.
8. The aluminum article of claim 1 , wherein the anodized coating does not exhibit a failure mode for at least four test cycles, wherein each test cycle comprises immersing for 45 minutes in an ultrasonic cleaning solution of general purpose cleaner solution, ultrasonic cleaning agent, and deionized water having a pH of about 12.5 and a temperature of about 70° F., rinsing with deionized water, immersing for 30 seconds in an enzymatic cleaner solution, and autoclaving for 45 minutes at 132° C.