Salt and vinegar for rust removal

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Sodium salts are quite soluble versus iron, you know. You've had ion replacement going on as well as reduction.

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Muriatic acid of the sort used for concrete work removes rust completely and in a fairly short order. I dropped some fine thread rusty bolts in this acid and left it overnight and the threads screwed into the correct size nut with no problem so the metal was not eaten away. The only posssible downside is that the metal is turned to an even light grey, possibly from very light etching
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Final report on the great Salt and Vinegar test :)
Before I hoik it all out and consign the tumblers to the dishwasher, I thought I would describe conditions (About 75 hours, I think)
The salt-and-vinegar solution has just about NO colour to it; it has NO effervescence; and a black scum on the surface. The nails are no different from before treatment except that they have gone blacker. There is a an amount of rust flakes on the bottom.
The "vinegar-only" still has slight effervescence occurring, and is a strong orange/red colour. The nails are no different except a little more rusty coloured. There is a similar amount of rust flakes on the bottom.
As a final twist, I decanted some of the clear orange liquid from the vinegar-only solution and added excess salt. Lo and behold, a black precipitate occurred turning the solution almost chocolate brown and opaque. I will leave this to settle, coz what I'm trying to see is if this purported ferric chloride complex is less orange than the straight ferric ion. So far, half an hour, the red colour seems to be persisting, so unless there is a marked loss of colour, that ferric chloride complex has not been demonstrated. Although the lack of colour in the vinegar-salt test could be because no ferric ions have been formed at all, just black ?magnetite?
My conclusion is that although the vinegar and the salt-and-vinegar cause some of the loose rust to fall off the very rusty iron, the treated surface is by no means cleaned. The appearance is not even perceptibly changed. I can't determine if one works better than the other, but from the colours of the solution and the rust and the lesser effervescence, I would conclude the the salt impedes the dissolution process.
I will rinse these nails and stick them back out in the rain and see which ones fall apart quicker.

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Sandy wrote:

(major snippage)
Sir:
You have WAY too much spare time on your hands.
Having said that The effervesence (sp?) may play an important role in rust removal , small bubbles forming in fine nooks and crannies of rust on the piece. As they get bigger they can mechanically, rather than chemically, loosen rust particles - similar to cavitation. However you get the rust off with an aqueous (sp?) solution, after rinsing and hand drying, wipe things down with a paper towel soaked with alcohol. Wipe things down again with a dry towel. The alcohol will grab any water left after the first "wiped dry".
charlie b
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That's a shame, but salt and vinegar is delicious on chips!
Ken Muldrew snipped-for-privacy@ucalgazry.ca (remove all letters after y in the alphabet)
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Interesting, despite what the others say! Your test about jives with my results, the most notable difference being the nearly clear vinegar/salt solution and the dark red (in my case) vinegar only solution. I would say that the iron did come clean by using the vinegar solutions, but required some brushing to really get all the rust off. I think it came cleaner than it would have had I not used the vinegar, but maybe there are better mechanical ways of doing that, or using a little muriatic acid and being very quick to rinse it off.
dwhite
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posted:

No, but then I didn't introduce that comparison :)

Well it's approaching 24 hours and I've just had 9 hours' sleep and the situation has not changed. Very pale yellow in the non-salt vinegar, and if you have a really good imagination, a very,very pale yellow in the salt vinegar. The nails have suffered NO observable change.

So why did he go on to assert that our discussion was irrelevant? Your explanation does not account for that. Seems he should have kept his mouth shut if he was no longer interested. There are many threads that I'm not interested in, and I just ignore them. When our discussion/experiments are done, we should have a clear conclusion as to whether it is at all efficaceous. With or without salt. WTF is off topic about that? Sheeesh!

So it is decidedly NOT off topic as Charlie was asserting? Look at the subject line. Many woodworkers are interested in deructing old valuable tools, or so I've read here.

No jargon in our discussion, sorry. Yes a few technical terms that are easy to find out about if you don't already know, and all technical subjects must have these terms and must deal with technicalities to understand them. Understanding brings ability to adjust for different circumstances, or so I find. Someone suggested that salt was excellent in vinegar solution for removing rust. I queried this as my basic understanding of chemistry didn't tell me why this would be so. I've now done an experiment that shows that vinegar with and without salt is virtually useless in derusting rusty ferrous metal. I always followed this in practice (never having had any successs with vinegar in the past few times I've tried it.) Adding salt makes no difference if you are generous. In my experiment, it was less effective than just the plain vinegar.

On what ground? It was NOT Off Topic. More than one of us was interested in it. And it was to do with derusting woodworking tools as per the subject header. And then what was the overall aim of his message? To have a whinge, No?

Interesting that you think it is useless. I've found through my life, that one of the handiest bits of knowledge I carry around with me, is my basic chemistry. It helps in just about everything I do.

And his point? Can't they just ignore it? I take it as read, that not every reader here is interested in every topic. I ignore most of them. I don't interject that the topic is OT.

Which it patently hasn't. The subject header says it all.

Then, by definition, it is ON topic.
I read Charlies message as someone being selfish and wanting no discussions that either he couldn't follow, or that he was not interested in. He should have ignored it, like most other rational posters obviously did. Does he often play "NetCop"?
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Sandy wrote...
<mucho snippage>

See the smiley? I was jesting about the discussion between you and me. (G)
As regards the rest of your post, you've made your points and I've made mine, so I guess we're done.
Cheers!
Jim
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posted:

Of course, and I was adding my 2 cents to the conversation.

Until we post our results, perhaps?

And to you too.
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