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.

 

[diytoolbox]

I have a question based loosely on the chemistry classes I took in high school, early 70's. That being an acid when mixed with a base neutralizes the solution to water and a salt. So how does mixing citric acid with the soda not reduce the effectiveness as it is neutralized?

Pete

Good question. Answer? I don't know.

 

[diytoolbox]

I have now used the citric acid, baking soda and squirt of handwash soap mixed in tape water solution for removing rust from my vintage wood carving gouges.

It seemed working very fast. Within 1 - 2 hours, the gouges rust were disappearing. After 3 hours, they were taken out from the solution, and rinsed in tap water, and dried with clean dry towel.

The rust seemed to have gone, but the metal of the gouges have dark grey surface now. They used to be shiny silvery surface before (with rust spots of course). But after de-rusting, the metals look dark grey on the surface? Why is that?

 

[Cozzer]

I have now used the citric acid, baking soda and squirt of handwash soap mixed in tape water solution for removing rust from my vintage wood carving gouges.

It seemed working very fast. Within 1 - 2 hours, the gouges rust were disappearing. After 3 hours, they were taken out from the solution, and rinsed in tap water, and dried with clean dry towel.

The rust seemed to have gone, but the metal of the gouges have dark grey surface now. They used to be shiny silvery surface before (with rust spots of course). But after de-rusting, the metals look dark grey on the surface? Why is that?

Pass.
Never had that myself, but in fairness most things I've done have been "dull" to start with...although the seized secateurs were shiny and still are.
From your previous posts I'd guess you were fairly accurate with your measurements (although I suspect they're not crucial to a few grams).
If so - and you can rule out the container? - there's only one element left.
The tap water.
Hard? Soft?
Could it really make a difference?
Find it hard to believe, but.....?

 

[Chris152]

I went to buy the stuff on amazon, had the washing soda in the basket, then saw the price of citric acid and realised it's not much more for the (very cheap) car battery we need. So that went in the basket instead and we ended up trying electrolysis. It's very exciting to watch all the bubbles fizzing away from the tool, I've yet to try citric acid but can't imagine it's as much fun!

 

[Vulcan]

The rust seemed to have gone, but the metal of the gouges have dark grey surface now. They used to be shiny silvery surface before (with rust spots of course). But after de-rusting, the metals look dark grey on the surface? Why is that?

This is what I have been saying. The acid has, however slightly, *etched the surface. Washing Soda and an old cheap battery charger Does Not do this.

I’ve used both methods a couple of times before giving up on Citric Acid.

* Others can be pedantic and use another term but it still amounts to surface damage, however slight.