How to slow/prevent corrosion of a steel post

I have a steel post set in limestone, about 18-20 inches deep, with some concrete around it.


I just noticed that I have about 6 inches of water inside the post. The limestone had a small seam in it and I believe the water seeps through it.
I am concerned about long term corrosion.


I am about to cap the post, so I will have no access to it in the future.
What can I do to prevent/slow the corrosion?


A. Nothing. Do not worry about it.  

 B. Fill the post with crushed limestone 12 inches above grade.  

 C. Fill the post with concrete 12 inches above grade.  

 D. Install a fitting in the post and dump some concentrated washing soda solution or powder once or twice per year to raise pH.  

 E. Some type of cathodic protection.  

 F. Other.


I am leaning toward B. This would be easy to accomplish and inexpensive, and limestone is supposed to raise pH level, which I think should slow corrosion.


