Applying Rust Killer to under carriage /frame any reason not to ?

Neutralize refers to "returning" to a pH level of 7 or somewhere thereabouts.
pH scale runs from 0-14. The lower the number the more acidic. To counter act the "acid", usually its wiped/rinsed with something "basic". Basic is the higher end of pH scale(lye) up to 14.
Hope that helps?
I understand pH and how neutralize an acid. I was just wondering if people actually rinse their parts with a basic solution after soaking in phosphoric acid. To me, that'd be a total waste of time. A simple water rinse works fine.