You may want to check out the Chemical Engineering Department at the University of Louisiana, Lafayette. Dr. James Garber P.E. is head of the department and has a very good background and offers advanced studies in the field of Corrosion.
I would have to say that the problem is caused by the thinning of the tin coating in the areas near the seams and the bottom crimp. The metal is "stretched" in the crimping process to make the seam and attach the bottom and in doing so it causes the coating to thin and cause holidays...
