I suspect if it is corrosion at the seams of the aluminum hood, it might be caused by a weld that introduced a dissimilar metal to the seam. There will tend to always be corrosion when two dissimilar metals are brought in contact. If this is the root cause of the problem then the only real remedy is a replaced hood that doesn't have that seam issue (assuming Ford has learned from this fabrication mistake, again, if that is the root cause).
Caymen is right on the lemon law. If you can show documented prove of three failed repairs within the period that lemon laws in your state apply (often 3 years), and you are still within that period (again, 3 years), then the Lemon Law can kick in.
But, since we are talking about and '05 and it is now '11, I don't think you can go back and get things fixed/replaced/compensated for on the lemon law statutes... a lemon law attorney would look at your case though, for free, usually.l
TJR