Corrosion resistant aluminum alloy substrates and methods of producing the same

1. An aluminum alloy product comprising:

(A) an aluminum alloy base having an electrochemically formed porous sulfate-phosphate oxide zone, the porous sulfate-phosphate oxide zone having a plurality of pores;

(i) wherein the ratio of sulfur atoms to phosphorous atoms in the porous sulfate-phosphate oxide zone is from about 5:1 to about 100:1; and

(ii) wherein the porous sulfate-phosphate oxide zone has a thickness of at least about 5 microns; and

(B) a silicon-containing polymer zone coupled to the electrochemically formed porous sulfate-phosphate oxide zone;

(i) wherein the silicon-containing polymer zone comprises a coating portion on a surface of the aluminum alloy base; and

(ii) wherein the silicon-containing polymer zone comprises a silicon polymer having a backbone of the formula —Si—X—Si—, wherein X is either N or O; and

(iii) wherein at least some of the silicon polymer is contained within at least some of the pores of the porous sulfate-phosphate oxide zone.

2. The aluminum alloy product of claim 1 , wherein the pores of the porous sulfate-phosphate oxide zone have an average pore size of at least about 10 nm.

3. The aluminum alloy product of claim 2 , wherein the average pore size is not greater than about 15 nm.

4. The aluminum alloy product of claim 1 , wherein the thickness of the porous sulfate-phosphate oxide zone is not greater than about 25 microns.

5. The aluminum alloy product of claim 1 , wherein the aluminum alloy is a 6061 series alloy.

6. The aluminum alloy product of claim 5 , wherein the aluminum alloy product is a forged product.

7. The aluminum alloy product of claim 6 , wherein the aluminum alloy product is a wheel product.

8. The aluminum alloy product of claim 1 , wherein the aluminum alloy product is capable of passing a copper-accelerated acetic acid salt spray test (CASS), as defined by ASTM B368-97(2003)e1.

9. The aluminum alloy product of claim 1 , wherein the coating portion of the silicon-containing polymer zone has a thickness of at least about 8 micron.

10. The aluminum alloy product of claim 1 , wherein the coating portion of the silicon-containing polymer zone has a thickness of at least about 35 micron.

11. The aluminum alloy product of claim 10 , wherein the coating portion of the silicon-containing polymer is substantially crack-free.

12. The aluminum alloy product of claim 11 , wherein the polymer of the silicon-containing polymer zone is polysilazane.

13. The aluminum alloy product of claim 1 , wherein the ratio of sulfur atoms to phosphorous atoms in the sulfate-phosphate oxide zone is from about 10:1 to about 75:1.

14. The aluminum alloy product of claim 1 , wherein the ratio of sulfur atoms to phosphorous atoms in the sulfate-phosphate oxide zone is from about 20:1 to about 75:1.

15. The aluminum alloy product of claim 1 , wherein the sulfate-phosphate oxide zone consists essentially of sulfur, phosphorous, oxygen and aluminum.