Rust removal with Citric Acid - pictorial step by step

[Twisted Tenon]

As an experiment, put some steel (plastic does not work) tent pegs out in the rain for a while until all are covered in a film of rust.

Then make up some citric acid solution and put in the tent pegs. After one hour take one out and scrub the deposit off - it will be rust free, and no pitting. Take out another one after overnight soaking and you will need to work hard to get rid of tiny pitting. Leave for 2 days and take out another one - this will be obviously pitted after removal of the deposit and grey (not shiny). Take out another one after a week and there will be severe pitting.

The Message

Do not leave in overnight, but use strong and hot solution - and check regularly - AND remove as soon as the rust has gone from the surface, ie you need to remove the gunk with a stiff brush and examine progress. If the metal is already rust pitted, then that is unfortunate but you can not get rid of those pits with citric acid.

Cheers
Peter

Thanks Peter, that's useful to know. I guess I have not really cleaned up anything with just light rust. Any pitting I have seen I figured was a result of the heavy rust already on the object. There is no pitting on the router blades though.

TT

[peterlonz]

I thought that the preferred method was to use phosphoric acid. Methods & results seem similar although I have never used citric acid in this way. The grey film left is iron phosphate which I understand to be itself "rust resistant". The car companies usually use this as part of their body treatment prior to painting. Tannic acid is sometimes used with phosphoric & leaves a brown finish, the tannins are said to increase further rust resistance.
I usually apply lanolin after the final wash & dry, available in a spay bottle, a little goes along way. Of course if you need to use your tools regularly, this is not ideal, maybe a light oil wipe in that curcumstance?