Hierarchically structured duplex anodized aluminum alloy

1. A method of growing a hierarchically structured anodized film to an aluminum substrate, comprising:

growing a Phosphoric Acid Anodizing (PAA) film layer to an aluminum substrate; and

growing a stepped growth Tartaric-Sulfuric Acid (TSA) film layer underneath said Phosphoric Acid Anodizing (PAA) film layer, wherein said stepped growth TSA film layer is applied by alternating a high voltage and a low voltage to form alternating TSA film layers which have different porosities.

2. The method as recited in claim 1 , wherein said stepped growth TSA film layer is applied utilizing a repeating ramped voltage.

3. The method as recited in claim 1 , wherein said stepped growth TSA film layer is applied utilizing a repeating stepped voltage.

4. The method as recited in claim 1 , wherein said stepped growth TSA film layer directly adjacent to said Phosphoric Acid Anodizing (PAA) film layer is initially applied utilizing the high voltage.

5. The method as recited in claim 4 , wherein a difference between the high voltage and the low voltage is greater than about 4V.

6. The method as recited in claim 1 , wherein the high voltage is about 15V+/−3V.

7. The method as recited in claim 1 , wherein said stepped growth TSA film layer directly adjacent to said Phosphoric Acid Anodizing (PAA) film layer is initially applied utilizing the low voltage.

8. The method as recited in claim 1 , wherein the low voltage is about 10V+/−3V.

9. The method as recited in claim 1 , wherein a difference between the high voltage and the low voltage is greater than about 4V.

10. A method of growing a hierarchically structured anodized film to an aluminum substrate, comprising:

applying a first voltage to an aluminum alloy workpiece within a Tartaric-Sulfuric Acid (TSA) solution to grow a first TSA film layer;

applying a second voltage higher than the first voltage while the aluminum alloy workpiece is in the Tartaric-Sulfuric Acid (TSA) solution to grow a second TSA film layer more porous than the first layer;

repeating applying the first voltage to the aluminum alloy workpiece within the Tartaric-Sulfuric Acid (TSA) solution growing another TSA film layer as porous as the first layer; and

repeating applying the second voltage higher than the first voltage while the aluminum alloy workpiece is in the Tartaric-Sulfuric Acid (TSA) solution growing another TSA film layer as porous as the second layer.

11. The method as recited in claim 10 , wherein the second higher voltage is about 15V+/−3V.

12. The method as recited in claim 10 , wherein the first lower voltage is about 10V+/−3V.

13. The method as recited in claim 10 , further comprising ramping to at least one of the first voltage and the second voltage within a predetermined time period.

14. A method of growing a hierarchically structured anodized film to an aluminum substrate, comprising:

applying a first voltage to an aluminum alloy workpiece within a Tartaric-Sulfuric Acid (TSA) solution to grow a first TSA film layer;

applying a second voltage lower than the first voltage while the aluminum alloy workpiece is in the Tartaric-Sulfuric Acid (TSA) solution to grow a second TSA film layer less porous than the first layer;

repeating applying the first voltage to the aluminum alloy workpiece within the Tartaric-Sulfuric Acid (TSA) solution growing another TSA film layer as porous as the first layer; and

repeating applying the second voltage lower than the first voltage while the aluminum alloy workpiece is in the Tartaric-Sulfuric Acid (TSA) solution growing another TSA film layer as porous as the second layer.

15. The method as recited in claim 14 , wherein the second lower voltage is about 10V+/−3V.

16. The method as recited in claim 14 , wherein the first higher voltage is about 15V+/−3V.