You're right bob. I should have said that pitting in the cylinder sleeves can come from electrolysis. I should also add that you have to have an electric current for electrolysis to occur. So, if all of your electrical components remain properly grounded you would never have an issue. Of course, in today's trucks there are so many components and the wiring just seems to get cheaper and cheaper that the likelihood of having a bad ground at some point is pretty good. Cummins and Cat both recommend using only distilled or deionized water in the cooling system.
This is just a link to a product brochure but it does list which components can be affected by electrolysis.
http://www.ve-labs.com/productpdfs/P...%20Revised.pdf