Citric dip trick

[mangocrazy]

The citric does stain the inner tank over time (or more accurately, the stuff it's removed from the metal stains it). Not found anything yet that removes the staining, but I just tend to live with it. Wouldn't be without it (them) now. Always buy the biggest you can afford, and in the smaller sizes I'd definitely go with one that has a drain tap.

 

[Screwdriver]

Probably nitric acid

Yes, nitric or hydrochloric acid. Between the two, they will dissolve most metals into solution. The two together is known as aqua regia, worth Googling if anyone is interested because the mechanism for those acids dissolving metal is quite fascinating. What happens is the metal reacts with the acid and displaces hydrogen so that the metal is now in solution. If you introduce a lit. more active metal into the same solution, it will displace the metal in solution. When a metal comes out of solution it forms a precipitate or a fine silt of pure metal. This I think is what sticks to the bucket, a very similar process to electroplating so it will be tricky to remove.

Warning though. Playing with acid is horribly dangerous. Citric is fine, I mean you can eat it so long as you don't tip it into your eyes, you'll be fine. Concentrated nitric or hydrochloric is in the realms of professional chemistry lab regarding the safety precautions you need to observe. A proper fume cabinet is absolutely essential. I wouldn't do it...

 

[Seadog]

I used some hydrochloric a couple of days ago to clean cement from a spade. Only 35% but was surprised to see it fuming. Over 50 years since I was in the chem. lab in school.
Fuming sulphuric was another favourite - H2S2O7

 

[cheb]

Fun fact: Aqua Regia was used to hide Nobel prize medals from the Nazis.

From: https://en.wikipedia.org/wiki/George_de_Hevesy

When Nazi Germany occupied Denmark during World War II, de Hevesy dissolved the gold Nobel Prize medals of Max von Laue and James Franck in aqua regia. During the occupation, it was illegal to send gold out of the country. If Laue and Franck had done so to protect the medals from being stolen, they could have faced prosecution by the Nazis. De Hevesy placed the resulting solution on a shelf in his laboratory at the Niels Bohr Institute. After the war, he returned to find the solution undisturbed and precipitated the gold out of the acid. The Nobel Society then recast the Nobel Prizes using the original gold.[13][14]

 

[Screwdriver]

I used some hydrochloric a couple of days ago to clean cement from a spade. Only 35% but was surprised to see it fuming. Over 50 years since I was in the chem. lab in school.
Fuming sulphuric was another favourite - H2S2O7

That is quite a strong solution.

"According to the EPA, occupational exposure can rapidly lead to swelling and spasm of the throat and suffocation. Material is extremely destructive to tissue of the mucous membranes and upper respiratory tract. Inhalation of hydrochloric acid vapors and mists produces nose, throat, and laryngeal burning, and irritation, pain and inflammation, coughing, sneezing, choking sensation, shortness of breath, hoarseness, laryngeal spasms, upper respiratory tract edema, bronchial constriction, bronchitis, chest pains, as well has headache, and palpitations. Inhalation of high concentrations can result in corrosive burns, necrosis of bronchial epithelium, constriction of the larynx and bronchi, nasospetal perforation, glottal closure, occur, particularly if exposure is prolonged. May be fatal if inhaled."

Careful now..

Me? I'm going to stick with citric. I may be reasonably cavalier with mechanically dangerous workshop activities but some of the more extreme chemical reactions are more than I am prepared to risk. There is an issue with "freedom of information" which allows the uneducated man (me!) to play with toxic chemicals. I was never any good at chemistry though and if in doubt, don't.

 

[Seadog]

Standard drain cleaner from my pound shop. Actually it was 32%.

 

[Screwdriver]

Standard drain cleaner from my pound shop. Actually it was 32%.

Stick it down the drain where it belongs.

Sad story, my long departed upstairs neighbours flooded the drains with hydrochloric acid. Left a puddle outside, cat walked through it, must have licked it off, killed her stone dead. Minna her name was.

 

[ukracer]

4:1 of what? By volume??

I suppose if you wanted to dispose of some bodies or dissolve your workpiece into solution. But then I would recommend Sulphuric acid for that or aqua regia for the other.

So imagine a plastic cup full of citric acid like this

How many cups of hot water would you add.
I just have a few rusty tools I

want totestit with. I have half a workshop full to drop in later but felt the need to do a timed test to start with as a base setting.

 

[sardine]

Citric acid is the dogs danglies, works faster if you keep it hot. Homebrew shops sell it in small amounts but its way cheaper to get a kilo off eBay.

 

[Dr.Al]

So imagine a plastic cup full of citric acid like this View attachment 232821

How many cups of hot water would you add.
I just have a few rusty tools I

want totestit with. I have half a workshop full to drop in later but felt the need to do a timed test to start with as a base setting.View attachment 232822

Don't overthink it. I fill a container with water (from a hot kettle if my aquarium heater won't fit in the container or from the tap if it will) then bung exactly some citric acid in. Leave it overnight (which is probably a lot longer than necessary) and take the stuff out.

I've got a small (maybe 750 ml) measuring jug that I often use to transfer the citric acid powder, but I don't even nearly fill it and I don't tend to vary how full it is with how big the container is (and hence how much water is in it). If you don't mind leaving stuff overnight it won't really matter. The biggest container I use is an 84 litre "really useful box"; with that half filled with water I use about 600 ml by volume of citric acid, but I probably use about the same when I fill a bucket with water.

With your cup of acid in that container, Put some hot water in the container and leave it for a few hours. I'm sure that'll be fine regardless of whether the container is half-full of water or full. Warmer water will make it go quicker so if the water's at cold tap temperature, you'll have to leave stuff in there for a day or two and maybe stir it around a bit part way through.

 

[AdW]

Just add enough water to cover what you want to re-rust by half an inch or so. The stronger the solution, the faster the reaction. If it is saturated and not all of the citric dissolves then it's not going to be an issue. Agitate it every so often.

If you want to stretch out the acid and time isn't an issue then just add half of the citric, you can always add more later when you see how it is performing or if it starts to become too spent and too slow/ineffective. Same goes for water as you can always add more later to cover any larger items.

 

[rtcosic]

Cheapest I've found.

Anyone found cheaper?

Love the GMO free label!

But is it Vegan?

I placed an order with that seller and it arrived yesterday, so that price is valid.

 

[lchris21]

Citric arrivo, used a cup full in about 15l...or so......parts in soaking overnight....before pics...

 

[dyno-tron]

I'm sure most are aware bit if someone isn't, the citric acid treatment also quickly removes zinc plating from nuts and bolts, great if you want to use them for welding projects and don't want zinc flu!
Btw, cheap Asda vinegar works just as well for removing zinc.

 

[anjum]

What is the best/ safest concentration of phosphoric acid which will remove rust or the most cost effective of achieving it.

Has anyone experimented with adding zinc oxide to phosphoric acid to give a light phosphate coating?

 

[lchris21]

So far so good. Went in a bit weak, so added another 1/2 cup. As AVE would say.....gonna let it chooch a bit longer

 

[ukracer]

So far so good. Went in a bit weak, so added another 1/2 cup. As AVE would say.....gonna let it chooch a bit longer View attachment 233140

What was it like before it went in?

 

[sardine]

Good for copper and brass as well, breaks down heavy crusty tarnish.

Things like old copper pans and kettles I use cheap tomato ketchup , leave it over night and it works a treat.