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The Shop => Finishing => Topic started by: sparky961 on October 10, 2016, 12:01:23 AM

Title: Citric Acid Concentration?
Post by: sparky961 on October 10, 2016, 12:01:23 AM
I have a new project that's starting out pretty rusty. I thought it might be a good time to try citric acid but not sure of the mix ratio and timed involved. Input or redirection appreciated.
Title: Re: Citric Acid Concentration?
Post by: awemawson on October 10, 2016, 02:30:12 AM
I use a couple of cup fulls of crystals in a two gallon bucket of warm water.
Title: Re: Citric Acid Concentration?
Post by: PekkaNF on October 10, 2016, 02:38:30 AM
Yesh. Even weak solution will do if you use hot water (and long time). Citric acid is nice because it does not stink.

Cheap alternative is to use vinegar. Works better again when heated, but it smells pretty much....I use it in the summer outside. Overnight eats away slag and rust away from hot rolled stock.

Both needs cleaning after, I use mild soap, stiff nylon brush and wear cloves.

Pekka
Title: Re: Citric Acid Concentration?
Post by: mcostello on October 10, 2016, 12:02:38 PM
 Cloves would smell nice.
Title: Re: Citric Acid Concentration?
Post by: sparky961 on October 10, 2016, 12:05:40 PM
Thanks, it would seem the concentration isn't too important.  Unfortunately I don't have a good way to keep it warm, but it can sit in the corner doing it's work.

I'll try to get some "before" pictures up in a new thread, but with all the different projects I always have on the go I tend not to document the work along the way anymore.
Title: Re: Citric Acid Concentration?
Post by: Auskart on October 10, 2016, 07:31:02 PM
http://metalworkforums.com/f65/t199727-citric-acid
Title: Re: Citric Acid Concentration?
Post by: sparky961 on October 10, 2016, 08:09:01 PM
http://metalworkforums.com/f65/t199727-citric-acid

Great link, thanks!

Anyone know if crystals are crystals, or if there are different strengths - perhaps cut with other benign ingredients?  The ones I used were originally from a bath & body products wholesale supplier.

Earlier this evening I used what I lad left over, which was about 50ml or crystals in 2000ml of warm water (because it worked for the container and part within).  It seems to be working, perhaps a little quickly so I'm checking on it regularly.

I, too, used to use hydrochloric acid on parts.  Frighteningly quick rust removal!  But yeah, nasty stuff to work with and nasty to anything nearby.
Title: Re: Citric Acid Concentration?
Post by: PekkaNF on October 11, 2016, 12:48:16 AM
I would imagine hat for cosmetic products, they would have much other stuff.

Here in finlad there are basically three sources:
* Farm supply shops. Looks like it is used to treat pigs, 5 kg pail is afordable
* Chemical suplly, not too bad if you need only a little
* Food/spice shops, but it is more expensive. Sometimes those pasltic tall industrial kitchen sizes are not too bad.

* Pharmacies are eye watering expensive.

Citric accid is nce to use, but not instant, specially if you cant heat it up to 60C and you need to scrub it clean, but it is nice to use and does not really ruin anything - including health. And recycling is easy, it does not harm sewer when diluted.


Pekka
Title: Re: Citric Acid Concentration?
Post by: seadog on October 11, 2016, 04:29:46 AM
I've used both citric acid and vinegar. They both seem equally effective and, if you leave the item for a long period, it doesn't have any noticeable effect on the base metal. My preference is vinegar and I've just cleaned a very rusty machine vice using it. I bought 5 litres of 99% acetic acid, from a supplier I've used before on eBay, and that should do me for a long time. It's certainly much more cost effective as it's typically diluted to around 5%.
Title: Re: Citric Acid Concentration?
Post by: Auskart on October 11, 2016, 03:54:16 PM
Citric Acid is also good for cleaning the Black Scale of hot rolled steel before machining or marking out  :bugeye:
Title: Re: Citric Acid Concentration?
Post by: AdeV on October 13, 2016, 05:37:43 AM
I've used both citric acid and vinegar. They both seem equally effective and, if you leave the item for a long period, it doesn't have any noticeable effect on the base metal. My preference is vinegar and I've just cleaned a very rusty machine vice using it. I bought 5 litres of 99% acetic acid, from a supplier I've used before on eBay, and that should do me for a long time. It's certainly much more cost effective as it's typically diluted to around 5%.

Hi Seadog,

How long did you have that vice base in the acid? Was the mixture warm or cold?

I ask as I have some exceedingly rusty cast iron drain covers I'd like to de-rust, and a nice long bath in either citric or acetic acid seems to be a popular and low-cost method of doing that.

Also, does anyone know what effect (if any) the acid would have on enamel? I've got an old metal bath which was waiting to go to the scrappy, but I might just re-purpose it, if the acid will leave the enamel alone...
Title: Re: Citric Acid Concentration?
Post by: Will_D on October 13, 2016, 06:40:10 AM
Also, does anyone know what effect (if any) the acid would have on enamel? I've got an old metal bath which was waiting to go to the scrappy, but I might just re-purpose it, if the acid will leave the enamel alone...
Bath Enamel is a form of vitrified glass and is therefore very acid resistant.

Glass and enamel do NOT like caustic solutions as they can dissolve the glass.

Check what the flug hole is fitted with as an acid may well eat away at the brass (of chromed fittings)

HTH will
Title: Re: Citric Acid Concentration?
Post by: seadog on October 13, 2016, 03:00:33 PM
How long did you have that vice base in the acid? Was the mixture warm or cold?

I left it for a couple of hours by which time it could be easily rubbed off with some wire wool. The solution was cold. I left the sliding jaw in solution for a couple of weeks while I was on holiday. It came out a treat.
Title: Re: Citric Acid Concentration?
Post by: AdeV on October 13, 2016, 07:11:29 PM
Thanks Will & Seadog  :thumbup:

Will - the plug fitting is chrome over brass (I assume), but if it gets eaten I'll just replace it with a plastic fitting. Looks like I know what I'm doing this weekend  :ddb:
Title: Re: Citric Acid Concentration?
Post by: sparky961 on October 13, 2016, 08:56:05 PM
So, it would seem finding a source for citric acid without the help of the Internet is rather tricky in these parts.  I've visited a local farm supply, and not surprisingly I had the guy at the counter stumped.  Pekka seems to be correct though in his statement that it's used as a food/water additive for pigs.  The guy said to leave my name and number and they'd check into it for me.  Of course, the last time I did that when I needed an air filter for my chainsaw I never heard from them.  Does it make me old if I think that customer service isn't what it used to be?

The online sources seem to be the way to go, though there's a huge price range and package size options abound.  The place I was going to get it, the same place the original stuff came from a while back, now wants to tack $25 CAD on any orders less than $75 CAD.  Then there's shipping, for which you generally have to go through the whole order and address entry procedure, only to choke out "WHAT THE .... ? You gonna deliver it personally by limousine for that??"

<sigh> ... I'm sure I'll figure it out.  I just wish it took less time to narrow it down to get the best value without ending up with a 10 year supply that turns into a solid chunk after a year of storage.
Title: Re: Citric Acid Concentration?
Post by: PekkaNF on October 14, 2016, 02:47:20 AM
Mybe people think automatically HAZMAT when they hear citricACID!

Maybe google translator will help on these ones:
http://www.biofarm.fi/tuote/sitruunahappo-vitapol/
Milka citric accid 99 %

"Acidification of the farmed feed (for pigs)

The powder can also neutralize the strongly alkaline new concrete floor by making it as strong as possible in hot water solution and brushing it on the floor and giving the floor to dry"

This is food grade citric accid (E330) it's bit more expensive at 29€/kg:
https://www.karkkainen.com/verkkokauppa/sitruunahappojauhe-e330-5kg

What about ethnic food shops? I think, I bought 1kg plastic bag of that from lebanese food shop looong timeago, they also had 1kg bags of MSG and other forbiden additives. :palm:

But if citric accid gets you stumpped, maybe normal pickling vinegar will do? Stinky though? Maybe a pail with a lid?.

Pekka
Title: Re: Citric Acid Concentration?
Post by: awemawson on October 14, 2016, 02:50:01 AM
I just buy it on eBay by the 10 kg drum
Title: Re: Citric Acid Concentration?
Post by: sparky961 on November 02, 2016, 06:58:20 PM
So, getting a bit OT and "after the fact" from the original post, but this still seemed the most appropriate place for the following.

A chemist, I am not.  I recall sitting in high school chemistry daydreaming while the chemical equations floated across the blackboard.... covalent bonds, ionic bonds, blah, blah, blah.  But one thing that stuck (or maybe it was from a Simpson's episode) was to NEVER mix an acid and a base.

Perhaps there are exceptions, or ways to do it well, but let me describe (with a rather bashful look on my face) what I've done and hopefully someone can tell me exactly what is _is_ that I've done, and if I was lucky - and maybe just how lucky.  Maybe it just looked worse than it was.

So, "citric acid solution disposal".... that's where we find ourselves.  I'm all done with the de-rusting described elsewhere on this forum, and in passing by the neglected barrel of acid tonight I noticed mold forming around the top and on the surface of the liquid.  So, this is nothing strange in my basement.  But I thought to myself: "if there's mold growing, it can't be THAT bad to dispose of it without additional precautions".  I live rurally, so no city sewers.  I did not want, nor was it convenient, to dispose into the septic tank.  My basement has a french drain (basically into the ground with some gravel around it) in the corner, and this seemed quite appropriate to safely dispose a weak citric acid solution.

Do correct me if I'm wrong because I have more to go.  I transferred about 1/4 of the barrel into the laundry tub where it slowly empties down the french drain.  I added a stream of fresh water to further dilute things as it was draining.

So, here's where things get interesting....

I thought I'd make an effort to bring the pH back to neutral (7) by the addition of a very small amount of lye (sodium hydroxide).  Into the full washtub (pH of about 4-5, to start) I sprinkled perhaps 2 tablespoons or so of lye across the surface.  At first, nothing much happened.  Then I noticed the bottom starting to change colour a bit.  Then I began to see "dark clouds" forming at the bottom of the basin....which quickly grew into an evil looking thunderstorm of blackish/blue churning through the water!  All the while, the tap continued to run diluting things.  This is well water, so no chlorine but other minerals for sure including high iron and likely some sulfur compounds by the smell some days. 

Anyway, the entire sink turned this dark blue/black colour but no noticeable odour nor extreme temperature change were noted.  I checked and I overshot on the pH with just that little bit of lye, with a reading of about 9-10.  I figured things were all good though, and proceeded to write this post before disposing of the remainder.....

I stand ready for education.  I promise not to doze off, as long as you skip the heavy math equations.
Title: Re: Citric Acid Concentration?
Post by: jcs0001 on November 06, 2016, 08:42:04 PM
Sparky

I can't educate you however am monitoring cbc for reports of a house and occupants disappearing :bugeye:

Please keep up regular reports so that we know you are still kicking :D

John.
Title: Re: Citric Acid Concentration?
Post by: sparky961 on November 06, 2016, 11:33:11 PM
They'll probably think its a meth lab or something...

Your concern is appreciated and all is well here.  I haven't been posting much because Ive been out enjoying the unseasonably warm weather in my kayak. Water is cold (10° C) but toasty warm in a dry suit.

Best I can tell from my own research is that I simply converted the dissolved iron compound (ferric citrate?) Into iron oxide. The form being blue/black and insoluble so it precipitated out and dank slowly to the bottom.
Title: Re: Citric Acid Concentration?
Post by: AdeV on November 07, 2016, 11:58:31 AM
Ok, returning to the titular subject of this thread..... how much citric acid monohydrate should I be putting in about 1/2 a bath full of water, to have any meaningful effect on a pair of heavy cast iron drain covers?

I reckon I troweled in about 5kg of the stuff... and so far (3 days) all that's happened is the acid has turned a greenish colour... As far as I can tell it's all dissolved, so it's nowhere near a concentrated solution...

Should I add more? Like the whole 25kg bag?
Title: Re: Citric Acid Concentration?
Post by: seadog on November 07, 2016, 12:03:39 PM
Have you taken a cover from the solution to see just what effect it has had? You may be expecting it to dissolve the rust off when, in fact, it usually stays apparently untouched until you attack it with a brush or wire wool.
Title: Re: Citric Acid Concentration?
Post by: awemawson on November 07, 2016, 12:05:35 PM
Are they Steel, Cast Iron, or Ductile Iron Ade ?

I use a couple of cup fulls in a bucket - no idea of the volume of your bath. Makes for expensive drain covers if you put the lot in - give it time, it;s presumably fairly cold?
Title: Re: Citric Acid Concentration?
Post by: AdeV on November 07, 2016, 12:26:50 PM
I'm pretty sure they're cast iron, judging by the weight and the fact one of them snapped when being extracted from under years of grime and roots...

I've scraped it with the trowel... haven't tried to get a wire brush in there. I'm not sure what concentration I've got so I didn't want to stick my hand in it....

Volume wise, I reckon there must be 100 litres? Bath is a standard 6ft thing, filled maybe 4" deep. And yes, it's c-c-c-cold.... (probably around 6-7 degrees C just now).

Time I have plenty of, they can sit there for months if necessary...  :thumbup:
Title: Re: Citric Acid Concentration?
Post by: howsitwork? on November 07, 2016, 02:41:21 PM
just give it time. If you want it faster heat it up a bit. Maybe smell a bit if it liberates any sulphur compounds form the iron or muck but it will clean. Add a bit of detergent to break up any grease/ fats on it. :med:

Re disposal of citric acid, just add a bit of sodium bicarbonate ( and prepare for frothing maybe) this is a weak alkali and will neutralize with no risk to you. When it stops frothing it's neutral basically.
Title: Re: Citric Acid Concentration?
Post by: sparky961 on November 07, 2016, 06:36:35 PM
There was less than 500g in the barrel I used, which was slmist filled with water. No idea of the volume but the blue poly barrels are pretty standard I'd think.

I ebded up sourcing mine as a 500g packet from a farm animal supply. Still have just a little bit left for other experiments.
Title: Re: Citric Acid Concentration?
Post by: sparky961 on November 07, 2016, 06:44:41 PM
There was less than 500g in the barrel I used, which was slmist filled with water. No idea of the volume but the blue poly barrels are pretty standard I'd think.

I ebded up sourcing mine as a 500g packet from a farm animal supply. Still have just a little bit left for other experiments.

I'm leaving all the typos in there as a historic relic for futere anthropologists to comment on the stupidity of tiny touch screen keyboards.
Title: Re: Citric Acid Concentration?
Post by: AdeV on November 07, 2016, 08:27:29 PM
There was less than 500g in the barrel I used, which was slmist filled with water. No idea of the volume but the blue poly barrels are pretty standard I'd think.

I ebded up sourcing mine as a 500g packet from a farm animal supply. Still have just a little bit left for other experiments.

I'm leaving all the typos in there as a historic relic for futere anthropologists to comment on the stupidity of tiny touch screen keyboards.

LOL! It could have been worse, I've seen some proper auto-spelling-correct howlers in recent times. My phone has a complete aversion to the word "van", preferring "can" instead...

Anyway, I think I've solved the cold problem:
(https://c1.staticflickr.com/6/5721/30548933440_817a2b5087_c.jpg) (https://flic.kr/p/NxvgAY)

The only problem with it is it's supposed to use screw-in gas canisters; so I'll knock up an adapter for it at some point to use a propane bottle... Pop that under the bath, light, add some more citric acid for extra flavour, slap a top over it, and we should be bubbling away nicely in no time :) And at only £6, if one isn't enough it's cheap enough to buy another one. Or two...
Title: Re: Citric Acid Concentration?
Post by: sparky961 on November 07, 2016, 09:14:27 PM
Make sure the stuff is cleaned of dirt, gunk, and grease. If not the acid won't do much.
Title: Re: Citric Acid Concentration?
Post by: awemawson on November 08, 2016, 03:37:50 AM
Ade,

You remind me of the woman I borrow Robert the Boar from each year. She lives on her grandfathers farm in a 'mobile home' with no bath. She has a Victorian cast iron bath with legs outside in her garden, and when she wants a bath she lights a fire under it. :bugeye:

Title: Re: Citric Acid Concentration?
Post by: hermetic on November 08, 2016, 02:00:19 PM
My workshyop is called Appletree Works for very good reasons, evry year I try to make cider, and end up with the most excellent rust remover!
Phil
Title: Re: Citric Acid Concentration?
Post by: AdeV on November 08, 2016, 04:26:28 PM
Ade,

You remind me of the woman I borrow Robert the Boar from each year. She lives on her grandfathers farm in a 'mobile home' with no bath. She has a Victorian cast iron bath with legs outside in her garden, and when she wants a bath she lights a fire under it. :bugeye:

Well.... that might end up happening down t'workshop in the summer months... probably not so much in the winter. Obviously I'll take most of the citric acid out first; just leave a little bit in there for that "lemon fresh" feeling  :lol:
Title: Re: Citric Acid Concentration?
Post by: howsitwork? on November 10, 2016, 04:57:20 PM
Ade

In winter you probably won't need the mankini to cover your embarrasement v :lol: :lol:

Title: Re: Citric Acid Concentration?
Post by: Will_D on November 10, 2016, 05:09:31 PM
My workshyop is called Appletree Works for very good reasons, evry year I try to make cider, and end up with the most excellent rust remover!
Phil
Hi Phil,

As a bit of a cider maker myself have a look here:

http://www.nationalhomebrewclub.ie/forum/index.php/topic,4308.0.html (http://www.nationalhomebrewclub.ie/forum/index.php/topic,4308.0.html)

We buy commercials pressed blended for cider juice every year. This year is 3,000 litres.

There is a lot of good info there.
Title: Re: Citric Acid Concentration?
Post by: AdeV on November 12, 2016, 06:31:39 PM
Pulled the drain covers out of the bath today... and it's definitely working, there's new metal visible, and much of the rust and crud has dropped away. Still a fair way to go, so I refreshed the acid & threw them back in - all 5 of them this time, instead of the 2 I was trying before.

I haven't taken an "after" shot yet, but here's what they looked like before I put them in the bath (they have been pre-jetwashed, but much of the crud is encrusted & wouldn't shift with just water...

(https://c4.staticflickr.com/6/5542/30944835275_0fec41d01e_c.jpg) (https://flic.kr/p/P9unqF)

(click for a bigger view)
Title: Re: Citric Acid Concentration?
Post by: sparky961 on November 12, 2016, 07:46:41 PM
Wow, those are nasty!  Much worse than what I was dealing with.

Glad to hear things are working though.
Title: Re: Citric Acid Concentration?
Post by: awemawson on November 13, 2016, 04:23:11 AM
Ade, those just need a tickle with the grit blaster and they'd come up a treat
Title: Re: Citric Acid Concentration?
Post by: AdeV on November 13, 2016, 06:58:40 AM
You may well be right Andrew, but they are seriously heavy lumps, and frankly I can't be bothered hauling them into the blasting cabinet - which, in any event, is in the other workshop.... I'll leave them pickling for a week or two, there's no rush. From what I could see of the first two, which have already been in for a week, they'll come out factory-fresh :)
Title: Re: Citric Acid Concentration?
Post by: awemawson on November 13, 2016, 08:32:09 AM
No I'd not suggest doing them in a cabinet blaster, more the Hodge Clemco proper big pot blaster like this:
Title: Re: Citric Acid Concentration?
Post by: John Rudd on November 13, 2016, 09:28:45 AM
Nice bits of kit those C-H blasting sets...
Shame I dont work any more, we had one in the shop with a decent cabinet that was good for home jobs.... :beer:
Title: Re: Citric Acid Concentration?
Post by: AdeV on November 13, 2016, 02:24:30 PM
Seems to be working  :)

(https://c4.staticflickr.com/6/5742/30874694731_a15e89a86e_c.jpg) (https://flic.kr/p/P3hT5X)
Title: Re: Citric Acid Concentration?
Post by: RobWilson on November 13, 2016, 02:46:27 PM
Ade

WTF did you get that colour  bath in this day and age ?     :lol: :lol: :lol:


Rob
Title: Re: Citric Acid Concentration?
Post by: AdeV on November 13, 2016, 03:57:16 PM
Heh - it spent most of the last 20 years in my bathroom, being the bath! Then it spent the last 10 months on my driveway waiting for the scrap metal man to spot it and take it away.

I can't vouch for it prior to 1995, as it was there when I bought the house!

I have a matching sink... and it is a rather nify shade of cyan, isn't it? People would pay good money for that colour, I reckon!  :scratch: