The joy Of Citric Acid

[scockram]

Just what I've been thinking.

 

[Vulcan]

^^^^^^^^^^^^^^^^^^^^^^
I have used both methods.
Never have I had the acid etching the metal.

Really, you couldn’t see the difference between the two? Using acid will etch the surface resulting in a matt grey finish. Using washing soda and a battery charger simply removes the rust, any shiny non rusty areas remain untouched.
I’ve seen many measuring tools and calipers etc ruined by attempts to remove the rust with acid.

 

[Jake]

The idea is that it makes sodium citrate, which is a chelating agent. Rather than just attacking with acid, that reduces the rust by pulling the iron out of the rust and into the solution. I think, being way over the ends of my crappy chemistry skis.