I'm remodeling my bathroom all the way down to the studs. I was about to hang another piece of sheetrock, when I discovered corrosion on a horizontal piece of vent pipe. I wiped the corrosion away and found holes, which range from 1/5 - 1/3" in diameter.

This is the top level of the house, and no water flows through this pipe. They are vents for a lower level toilet and sink.

What can I do to stop the corrosion, and keep them from getting worse?

As you can see in the picture, it would be difficult to replace this section. (Well, at least for me!)

Michelle in Machesney Park, IL