True rust removal by a chemist - acids compared

[@mbahismu4156]

Phosphoric acid is mainly for phospating, not for rust removal. It will create black coating of iron phosphate that will prevent further rust (passivation), both form rust and from the iron itself. Only minimal damage (deformation) made to the workpiece. The reactions are: * Rust: 2 H3PO4 + Fe2O3 --> 2FePO4 + 3H2O * Bare metal: Fe + 3H2PO4 --> Fe(PO4)3 + 3H2 Those coating (FePO4 & Fe(PO4)3) won't dissolve into the solutuon. That's why it didn't got dirty, and can be used again (if still has enough concentration). This is the winner for common use in my opinion. On the other side, hydrochloric acid did best in rust removal. But it will damage the workpiece to some degree, and then exposed steel to air will rust immediatly. The rust dissolve in the solution, and the acid then attack the exposed steel. That why it turns dull, and will rust faster in the future. Next removal will add more damage. The reactions are: * Rust: Fe2O3 + 6HCl --> 2FeCl3 + 3H2O * Bare metal: Fe + 2HCl --> FeCl2 + H2 This is not a good choice to preserve the workpiece.

[@evadevries2952]

Agreed. Bottom line: Hydrochloric to remove rust...Phosphoric to convert rust. I like to grind flush and then use phosphoric to convert rust that exists below the surface plane. Note, if you rinse phosphoric while wet you can apply epoxy primer. If you let it dry, epoxy will not adhere.

[@Mavrik9000]

Please also explain the formula for (vinegar) acetic acid with iron and iron oxide, and the pros and cons for using it.

[@mbahismu4156]

​@@Mavrik9000 both iron and iron oxide will forms iron acetate, similar to HCl but slower reaction. Pros: safe to skin and cheap. Cons: slower reaction and requires cleaning / neutralizing afterward.

[@Good-Enuff-Garage]

@@evadevries2952 I have used Hydrochloric acid to remove the rust off the hood of my truck because I assumed acid was acid and I always use Phosphoric, anyway the hood rusted so bad in less than a year I had to redo it with Phosphoric acid

[@vevenaneathna]

unlike with the other acids, the chloride ions can easily subsitute the iron oxide and change the cordination complex structure which then becomes more soluble. this is why you can add table salt to almost any acid to speed up its ability to disolve rust. not sure if the chloride ions can imbed themselfs the bare metal and migrate below the surface layer. boiling water actually converts the iron to a black oxide and is the least damaging way i know of to "remove rust" because you actually convert it into a passivized surface layer. when it comes to pasivation like with phosphoric acid, i believe you actually want the most concentrated solution possible. this is definatly the case with fuming nitric acid which is less reactive than dilute nitric acid because of pasivation

[@darkerbinding6933]

Love that you got out the CRC Handbook of Chemistry and Physics. 👍

[@borna430]

I had a classic car with lots of rust on it. after I stripped the paint, spray the rusted area with Ospho which is Phosphoric acid, which turned the rust to Iron Phosphate (black stuff). Then epoxy primer it and painted it. 10 years later still good as new. So when it comes to auto restoration, phosphoric acid is the number 1 winner :)

[@mikebetts2046]

This whole test pre-supposes that speed of removal is the main goal in removing rust. But this is not always the over riding goal. Sometimes it is more important to convert the rust into a less reactive form. Or to remove it delicately to reduce damage to other items.

[@firmbutton6485]

Id usde hydrochloric, wash tat off then use phosphoric to convert any remaining...?

[@bitTorrenter]

@@firmbutton6485 Yes, I think Phosphoric Acid is a good option.

[@jdsmort]

@@firmbutton6485 Agreed.. Hydrochloric actually reacts through the rust (complex hydrated oxide of iron) and reacts directly with the iron, this causing the rust to 'fall off.' The phosphoric will react, albeit slowly, with the actual rust, and will also react with the iron to form a 'skin' of iron phosphate which is a blackish colour, and is semi-impervious. That is why it is the rust treatment.. but generally you need to remove the worst flaking rust first when using Phosphoric acid.

[@embuscadochifreinexplicaca5960]

@@jdsmort Hi, sorry to bother you, but is it a good option to use hcl first, then phoshopic / acetic and then a zinc spraying to prevent the rust from coming back, or does the phosphoric create a protecting barrier already? Because the acetic certainly doesnt, atleast at white vinager concentrations ahah And how do you clean hcl / phosphoric acid off metal parts? Simply using water? Or is there a possibility can they react with it, despite the low quantity of acid already present on the surface?

[@jdsmort]

@@embuscadochifreinexplicaca5960 Hcl is just Hydrochloric acid... and can be cleaned with water, If you want to neutralise it you can wash with a mix of baking soda in water... ends up making salt.... Phosphoric is a weak acid and can be just washed off.. with parts it is easiest to wash off with boiling water which then allows the part to dry quickly. Acids don't react with water, they just get diluted more.

[@TonyWadkins]

Hey Ken! Thanks for the scientific method of analysis. One note about phosphoric acid if my memory serves me is that it creates black iron phosphate which acts as a rust inhibitor. And watch out for hydrogen embrittlement when using hydrochloric acid. Not critical for everday objects but might be important for more critical tools where strength is important.

[@Ken_Sweden]

Good input. Thanks for your comment!

[@TigDegner]

Thank you for mentioning hydrogen embrittlement from - something I as an everyman will now be checking into. My plan had been to use a brief HCl bath to remove the bulk of rust from some old tools etc., rinse in water, then finish with a H3PO4 soak to convert the rest and protect the pieces. This is a process mentioned in the comments on another video as being used by a Biomedical Repair Technician, but as my application does include tools the embrittlement is a concern. I'd welcome any further thoughts on this. Thanks again!

[@AldoSchmedack]

Finally a chemistry experiment on YT that gets recommended that actually has a practical everday use and not just use in a lab. Well done and subscribed! Looking forward to watching more of your videos sir! Paul from Iowa (PS I *love* chemistry at work!)

[@Ken_Sweden]

Thanks for feedback!

[@Pepegapl]

phosphoric is what a lot of people here use for relic restorations, when used in low concentrations it can remove the rust while not destroying the original paint

[@hrajabi7261]

I still go for electrolytic rust removal in Na2CO3, it's less destructive to iron piece

[@bigoldgrizzly]

I totally agree. This is my go to method for any type of conservation work. Where there is a lot of paint to come off with the rust, I used to use sodium hydroxide [lye] as the electrolyte. Works very well at removing paint and rust but careful as I was, I always ended up with some small alkali burns from splashes. I now use commercial paint stripper, followed by washing soda electrolysis

[@helderblsba]

Excelent. I never see this kind of video on YT with that details and quality. Congratulations!

[@Ken_Sweden]

Thank you. I appreciate your kind encouragement!

[@أمالدنيامصرالغاليه]

@@Ken_Sweden can you mentioned the ph of HCL Acid and Glacial Acetic acid, thanks

[@jessejarrett2537]

Ive used HCl for a long time on rust removal (Muriatic acid) it's super cheap an works every time. Also cleans concrete shop floors in seconds ! But make sure to wear a respirator.

[@PaulG.x]

It's good to find a comparison test using proper scientific method and knowledge of the processes involved

[@SgtJoeSmith]

The phosphoric acid isn't supposed to dissolve the rust it neutralizes it into black oxide. Leave it full strength, dip spike in and pull it back out and process is pretty quick. The bubbling you see in the hcl is your good metal dissolving. Leave spike in a week and it'll be gone. The hcl etches the metal heavily which is great if you gonna primer and paint but may not be desired other times. Evaporust and electrolysis are other options too. Just depends type of item, how heavy rust is, what's your end goal for rusted item. Different situations call for different products

[@Ken_Sweden]

Another top comment in 10 hours, bringing more information to the topic. 👍 As said here, the bubbles are from the pure iron reacting. I believe a concern that has come up is the possible hydrogen embrittlement that some YT watchers have heard about, especially for applications relying on mechanics strength. I have little quantitive information on this apart from that rust dissolves several orders of magnitude faster than the iron, and that some texts state that it is reversing on heating. If anyone wonders - lug nuts wheel fasteners and other similar applications - just exchange them to NEW ones.

[@TW-vw4ss]

Good point

[@brunoleonardo3315]

Nice video! Two things that I haven't seen covered by any youtuber (until now) on the rust removal topic: 1. How does different metals (aluminum, brass, copper, etc) and/or steel alloys react to each of the acids; 2. What does the acid bathe does after medium/long term exposure, structurally-wise to the materials (how long for rust to come back and does it come even harder on the surface? does the acid messes with the material physical properties making it brittle, etc?). A lot of people look for options for treating hand and bench tools (wrenches, vises, etc) and cars, and those would come very handy. Thanks for the video, quality stuff there. :)

[@JP-wx6uh]

HCl is indeed very efficient although it is extremely aggressive. Perhaps you could try doing a slow process of de-rusting by using Formic acid? Formic is used in clinical pathology because it decalcifies bone tissue without destroying the bone material itself.

[@bigoldgrizzly]

....... off to collect a couple of million ants .... brb :

[@linolino]

beautiful experiment, too bad that there is no citric acid and oxalic acid

[@vcash1112]

They are weaker acids, so what's the point?

[@stanbest3743]

I use phosphoric acid as it forms hard dark blue adhesive layer on the steel ideal for painting then cavity wax or similar. If penetrating oil fails, hydrochloric acid, but good advice here, be careful it can hurt you and dont leave it on for days it can damage the metal

[@bernardmauge8613]

thanks for posting. I have a rusty frame on a big welder and after grinding I need ti remove the rust in the pitted spots before applying an epoxy. I will use cyour recomendation.

[@facereader99]

That is the proper scientific way to compare. One can say that the thickness of rust may have been different on the different bolts but the results show that would hardly make any difference. Need to find HCl now. Thank you very much!

[@robfrost1]

Thanks. A useful video. The HCl still bubbling after all the rust is gone, indicates that it's now removing the iron, confirming what a bad choice it can be for conservation, or at least the care which must be taken. Phosphoric acid is used because the iron phosphate salt remains on the surface and passivates the steel.

[@Ken_Sweden]

Good input. I have to correct some aspects of your statements for our followers. The HCl is still bubbling as long the acid is reacting with the iron, and although here suggested that phosphoric acid would be different in terms of reactivity, it is wrong. The phosphoric acid leaves a porous iron phosphorous coating, which is black and covers your part however, since it is porous, the hydrogen is still reacting under the coating. This is meaning that if you leave your rusty iron part in the acid for 3 weeks, also with the phosphoric acid, the part would be completely eroded. You can try it, and you will find out this yourself. Now, phosphoric acid is a weaker acid than hydrochloric acid, so everything will take a longer time, but as with all acids, if you raise the temperature 10 degrees, that is equivalent to a double concentration of your acid, so the process can be speeded up. The maximum concentration of phosphoric acid is about 85%, whereas hydrochloric is 37%, so the hydrochloric reacts vigorously with water and even the water in the air. This means that everything above 37% will automatically go into a gas (read the concentration on the bottle, and you will find that there is nothing like 100% HCl). Be aware of this when you open a bottle because it will smoke out in your face as concentrated hydrochloric gas acid gas, while 85% phosphoric acid is a liquid, and no problem opening the bottle. In other words, extreme differences in reactivity. In practical terms, this means that your rust will dissolve at least 10 times faster with hydrochloric acid compared to phosphoric (rough statement and relative to the density of the rust you have). Now, the major benefit of phosphoric acid is that it will provide you with a good surface for painting. The phosphoric acid counter ions, i.e., the phosphorous ion, are not catalyzing further rusting as the chloride (called hypochlorite ion) will do. In fact, all hydrochloric-treated iron must immediately be neutralized completely on the surface, which could be difficult for a DIY person at home to verify. This means that in the worst case, you have hydrochloric remains left, and you paint over it, only to find that you have put an acidic rust-promoting layer between your paint and your iron part. Terrible, of course, so here one can find a good reason to stay away from the hydrochloric acid and instead go for the phosphoric acid. However, always expose your parts to minimal acidic conditions because every acid can bring hydrogen embrittlement of your part, meaning that it will fall apart and crack much more easily than a new part. Some studies say that hydrogen embrittlement can be avoided by heat treatment of the iron after acid treatment. In reality, at this point, most people would go and buy new things to replace the original item. Because, on top of the rust elimination process with acid, you would need a several 100s k USD microscope to verify if you have removed diffusive residual pathways in your iron (by any heating activities). You would also need to do mechanical testing if you are going to use your things for space missions. Cheers.

[@gabbermaikel]

@@Ken_Sweden but most diy rust removal is either for show things, like a piece for a fence or something for on their wall. Or its going to be car bodywork, wich i dont really think hydrogen embrittlement would be a problem on unless you get a real bad case of it. But stil a great test here, something that really proves the effectiveness and not some corporate BUY OUR CRAP thing. And then some more words in the comments from you and other to make it even better. And fyi, there are rust removers out there that use HCl, i dont know the brand anymore. Seemed like a strange choice to me, and you kind of confirm that in this comment. It works really fast, but how do you know if you got rid of the last bit of it? You probably dont know. And i have seen what happens when you get something acid dipped and then painted and find out afterwards the guys that did the acid dip didnt neutralise it properly. Paint fell off and the thing was rusting faster then you could imagine.(dont know what acid they used tho)

[@robfrost1]

thanks @@Ken_Sweden for the comprehensive reply. What I can say, from an empirical perspective, is that Phosphoric acid always gives me a great etch and long-lasting paint afterwards. Iron phosphate is barely soluble in water whereas both ferrous and ferric chloride dissolve easily and remain acidic.

[@andvil01]

I use citric acid. The water turns green. Very effective with a little heat.

[@dimmacommunication]

Me too

[@pubbiehive]

Try oxalic acid.

[@bitTorrenter]

And it isn't as polluting to the environment as Nitrates and Phosphates formed when using their respective acids.

[@vicmills7702]

As a Chemist, great video. I find feraclean is a very fast acting acid that removes rest even faster than hcl I put feraclean in my central heating for 1 hour then emptied it and I think the heating is the best it's ever been. Didn't get hot until I did it, and after flush I think it was clean as it was once new.

[@ghraffydd5275]

I find phosphoric acid works fine, but takes longer. The concentration doesn't seem to matter but it does alter the reaction time. It doesn't seem to remove appreciable amounts of good steel. Hydrochloric acid cleaned items get eaten away badly if there is much rust to remove and even after neutralising it I find the cleaned steel continues to rust badly. I also find any steel near where you were using it rusts. Those nails would go in my drum of molasses and water, two weeks later I would pick them out and they would be spotless.

[@victimovtalent6036]

My favourite is using phosporic acid cause after removing rust its takes long time to becomes rusty again

[@Ken_Sweden]

+Asep Saepudin good point. Phosphorus treatments are also often used to prime before painting. See for example my failing attempt to use POR - 15 paint directly over rust. The missing chemical was a phosphate primer

[@harleydavidson801]

Ken Sweden I apply boiled linseed oil after acid has dried on the underside of my van an the rust never returns

[@Ken_Sweden]

Many folks are looking for what you mention, and spend big bucks on anti-rust paintings that are sometimes useless. If you by any chance are in northern Europe, and visit a historical site with old cannons, you may wonder how they preserve these iron cannons safely for generations. The answer is a combination of what you mention with lead oxide, only allowed with special permits at cultural restoration sites. I will go into paints and preservation in later videos. In your case the linseed oil has likely crystallized as an impermeable layer towards water and works even without the metal oxide. Great input, and very interesting. Thanks for your comment.

[@diyertime]

If you had prepped it with phosphoric acid prior would por15 have worked? or another way to word the question is phosphoric acid used to create a phosphate primer.

[@Ken_Sweden]

hopelessDiy ...possibly it would but the one component POR - 15 is still a one component paint so it does not cross-link like 2 component paints and is therefore always inferior in mechanical strength. This is the reason all fibre composite aimed for performance parts and airplanes etc always are impregnated fibres with 2-component thermosets. The thermosetting is the reaction between the components, making it insoluble, and rock hard. Sorry for late reply, missed this one somehow. Thanks for input and good comment. 👍

[@idontknowmyfirstname69]

If you ever decide to do another comparison, i would like to see how the different acid's compare in effectiveness with some chelating agents

[@Ken_Sweden]

Amines? Interesting comparison, and I may do it for educational purposes.

[@scottcates]

Molasses, definitely

[@scooter133]

Hydrochloric acid.... Chlorates are oxidizers. if chlorates bond with iron, they embed in the steel. Basically, it chlorinates the steel. The result is corrosion/oxidation at an accelerated rate? It removes the rust, but how do you stop the Chlorates from continuing to work on the steel? I've heard that it can slowly eat away at the steel even years after?

[@SnorrioK]

Another good method of getting rid of rust is with an acetylene/propane+oxygen torch. Just remember to wear glasses because the rust sort of explodes off into your face. Something to do with the metal expanding while the rust doesn't I think.

[@Ken_Sweden]

Coming up as a test. Best ideas gets evaluated in the lab. Thanks.

[@Ken_Sweden]

Good suggestion from KZbinr above. Thanks. Here's the video: kzbin.info/www/bejne/eWGbnWWMbLWdg6s

[@phiksit]

Also works for cleaning mill scale off hot rolled steel.

[@olitonottero7620]

Super helpful thank you !! Does this mean that if you let the rusty nail sit in Acetic acid (HAc) for x times longer than the nail soaked in Hydrochloric acid (HCl) then the final result should, in theory, be just as good, or am I missing something here..?

[@Yuchub33]

can cationic surfactants (neutral ph) work to remove rust?? was thinking of ways to remove rust without acid pH

[@drnotebook]

This is the best rust removal videos of more than 10 that I have watched. Simple, effective, and to the point. I am shocked at how un-scientific and illiterate some of the videos are. Some commercial rust remover product vendors could even spell acid names correctly. (RustAway spelled Acetic Acid "acedic acid").

[@voidisyinyangvoidisyinyang885]

"I would not use sulphuric acid for de-rusting steel, phosphoric acid is much better as it leaves the surface etched with a layer of iron"

[@ibrahim-sj2cr]

i was looking for chelating agents such as pentetic acid or EDTA

[@Ken_Sweden]

I think there is a classic amine someone mentioned here in the comments

[@bitTorrenter]

You could also have tried Citric, Peracetic, Sulphamic, Iodic, Oxalic, Formic, Lactic and Tannic.

[@bigoldgrizzly]

Can't say I have tried all the other acids, but tannic acid acts as a converter rather than a remover of rust ! The iron oxides [rust] are converted to ferric tannate which is a black compound, which is durable, very stable and deters further rusting. I use this on a regular basis in conserving old tools and artifacts. Tannic acid is very safe to work with and non poisonous - I know since I consume a lot in the form of common or garden tea. Tannic acid is used in many commercial rust converters.

[@Andrew_Sparrow]

If left in the acid would the metal be dissolved? If so is there one acid that would remove the rust but not the metal better than another?

[@Ken_Sweden]

Good comment. I will take one of the bolts and leave it in there for weeks. You will have an answer. However, in here the rust is so porous and sensitive to the acid that once the rust is gone, what you see is an almost dead reaction (judging from the gas evolution as bubbles)

[@philipoien7562]

I've used phosphoric acid for rust removal for over 30 years. I bought a gallon of 97% liquid and started experimenting with different concentrations of only acid, and then with the addition of 2-butoxyethanol, which I found listed as a component of "metal prep" used here in the US in autobody shops to treat surface rust. 2-butoxyethanol is a surfactant used in cleaning products. The saddest day of my experimenting life was the day after I put a brand new, but surface rusted clutch pressure plate and a perfectly functional but slightly rusty clutch cable for a VW-Porsche 914 in a 5 gallon bucket with 15% acid (the concentration listed on the commercial metal prep) and left it to sit over night. In less than 8 hours, the acid had completely dissolved all the thin steel parts. The spring steel that held the inner contact plate to the outer cover and flexed when the clutch fingers were depressed was gone, and the only thing left of the cable was the coiled housing, inner nylon liner, outer black rubber cover, and the cable ends. Don't leave thin steel in acid for hours.

[@diyertime]

You are on to something Andy. On my car sulfuric acid spilled off my battery onto its holder. It ate the paint off and created a lot of rust in the area. Now I'm using phosphoric acid to clean the area up and repainting.

[@chrisz.9974]

Ken Sweden is there an update on this?

[@metallitech]

This has been tested by a youtuber somewhere and the answer is yes. If you leave it in for months then it dissolves the metal.

[@chrislambe400]

Flask Hals? Interesting that German for neck Hals is the same in Swedish. Wikipedia says old Norwegian and Polish too.

[@Larry-d3i]

First off, I am also a chemist. My degree was finished in 1964, a BS in organic chemistry. I have worked in the field mainly as a polymer chemist, but also in other processes, mostly as research and development of new products and processes. The problem I am dealing with now is flash rusting of cast iron after dissolving rust with a muriatic acid bath. Could you please detail your preferred method of neutalizing the acid and protecting the cleaned metal from oxidation? I am cleaning badly rusted cookware so it will need to be safe for food preparation. Thanks and congratulations on your video.

[@berntd]

Is there any truth in the information that that HCL will cause future corrosion/rust in the treated metal and the phosphorice will not as it forms a layer of phosphate ?

[@Ken_Sweden]

Yes the chloride ions have a catalytic effect on the irons ability to rust. It is also true that phosphoric acid will leave a phosphorus iron layer on top of the acid cleaned iron. This layer is, however, extremely porous although not visible to the naked eye, meaning that water will penetrate though it in humid environment, and the rust will continue under the iron phosphor layer. It’s therefore always needed to create a barrier agains the humidity, by painting the iron phosphorus layer, for example. The more impermeable this layer is, the better rust protection you will have. Some people would advocate that you prime your part with a zinc primer, a paint that will let the zinc oxidize first, before the rust start forming. A top seal that really keep the water out is always the best protection. That’s why the best anti rust paints used on 17 century preserved cannons in historic castles are preserved with some tar like thick black paint. It is not for sale because it is based on lead containing formulations. I hope this helps, and have a good one!

[@nigeltegg]

Great video from the view of a chemist, but where is formic (methanoic) acid? It removes rust pretty quickly, but converts it to ferrite (iron(I)oxide) which is easier to remove with detergent, before metal is painted or oiled.

[@matthewjenkins1161]

Phosphoric may be far slower, but won't immediately flash rust after rinsing the acid off, like the others will. The rust remaining in the Phosphoric acid example, will have been stabilised and future rusting inhibited.

[@Ken_Sweden]

I think you are right. For more severe rust I nowadays use the hydrochloric, then I neutralize with sodium hydroxide toilet cleaner and in the end, if there is any signs of anything left in red brownish possible flash rust, then I do a final dip in phosphorus. Almost like you say. Thx for comment

[@neodiy]

How to prevent more rust forming after the metal is cleaned...because i found that it gets more rust than ever after using phosporic acid or hydrochloric acid to clean metal rust

[@Ken_Sweden]

A method I’ve heard should be great is to heat up the metal piece to almost starting to become red, and then drop it into motor oil. I see your problem with hydrochloric acid but you should not have that big problem with the phosphoric acid

[@bobcatt2294]

Phosphoric Acid is safer and like that of lime juice - food grade. Phosphoric Acid also is less evasive on metal and plating.

[@bernardmauge8613]

If it still rusting after rinsing it is because the acid is still active on the metal surface. You need to rinse it again with water/baking soda for passification.

[@Ken_Sweden]

Correct for sulphuric and hydrochloric acid!

[@apuuvah]

Hydroclorid acid and sulphuric acid will eat metal too. Phosphoric acid wont. It converts iron oxide (rust) to grey/black iron phosphate. It needs to be 30-60% phosphoric acid. Cold temps slow down the reaction dramatically. No need to remove before painting.

[@ml.2770]

I normally use citric acid to remove rust, followed by a rinse and quick dip in evaporust to prevent flash rust.

[@Ken_Sweden]

Its a good One, but it takes time. Heating the citric acid makes a huge difference.

[@ml.2770]

@@Ken_Sweden I'm in no rush.

[@michaelshults7675]

Good information. As far as dissolving steel particles embedded in a Vitrified aluminum corundum oxide sharpening stone .. These stones are resistant against acids. I have actually soaked a stone in full strength 32% hydrochloric acid for a week and it didn't eat out all the steel. What do you recommend? I even added 98% sulfuric acid to the muradic acid outside in a glass container and it helped but not 100%

[@Jurica-mtb]

Hi, what are you opinions about HCl and H2SO4 in practical use to remove rust from the inside of the vehicle's gas tanks? Problem is that the inner surface of the tank is not easily accessible so it is very hard to wipe the rust after chemical reaction.

[@Ken_Sweden]

My opinion, in that case, is to use only the required acid strength but to add some small stainless steel balls, about a coffee cup, and then let them work their ways around with the acid. 3-5 mm would do the job perfectly. If you have to go all the way to HCl, then you will inevitably have some flash rust forming when it dries, and so the chloride ions need to be removed. I would then flush it with baking soda (as many spoons you can add to a water solution while still having a good liquid) and finally, I would do a rinse with the phosphoric acid. this last step will give you very nice sturdy priming of your inner tank surface although if properly cleaned from previous rust, it will only be there as an invisible layer that prevents further rust from forming.

[@sherp2328]

hello, i love this video. been trying to find correct cleaning solution for following two problems. first old glass bottles i dug up that are etched and also stained. second rocks lots of rocks i also dug up are stained with rust. could you recommend the best solution for both. thank you very much. happy holidays!

[@trinitytoo]

Check out muriatic.

[@passage2enBleu]

The oxidation in my brain has been treated. Chemistry is to me what oil is to water. Thanks for the practical value of your experiments.

[@voidisyinyangvoidisyinyang885]

tannic acid in tea is also used for rust converter on cars

[@davidware8845]

Sulfuric needs to be heated before it effectively removes rust. Steel will not pickle any more quickly beyond 13% sulfuric to 87% water. That's the sweet spot.

[@Ken_Sweden]

A great comment. Thanks. Do you have any links on time-temp correlations for different carbon content? I see that both HCL and sulphuric are used , but as you said the sulphuric probably needs a bump in temperature. I did cut up a nail that I had in the HCL for 1 week and with that long exposure, that acid had penetrated as rays along what I believe is possibly some more carbon rich boundaries. In direction along the nail.

[@Canuck51]

Ken Sweden, thanks for the very informative video. I've been working on a small restoration project and have been using both an inexpensive acetic bath (undiluted white vinegar) and sulfuric baths (diluted "Clobber" drain cleaner), with different results. Your explanation of pKa values explains why!

[@r1w3d]

Sulfuric acid just cleaned a bike chain in around 2 minutes and gave a nice black oxide layer which will hold onto oil much better. Just have to sit and watch it because it works super fast. What grade of sulfuric acid did you use? I actually had to dilute my acid with distilled water which made it pretty angry for obvious reasons. With water the reaction was extremely fast for chemical rust removal.

[@faheemandrews3795]

I need the best formula for iron remover please 🙏

[@jozsefizsak]

I just spotted this very interesting video. Am I overlooking anything or does it make a lot of sense for someone in an apartment to simply leave things in vinegar for a couple of days to maybe ten days, until all the rust is dissolved? It's just so simple, inexpensive and safe as long as there is no rust removal emergency that requires great speed. I do think the cleanup is a little messy which is why the electrolysis is appealing.

[@Ken_Sweden]

+Jozsef Izsak yes, in the long run the action will be the same as long as you have an excess vinegar acid. Vinegar is only about 5% concentration of acetic acid so it might take awhile. Thx f good comment!

[@dimmacommunication]

HCL is gonna weaken and permanently affect the steel. Also you should try Citric acid

[@praja7491]

Is that true??? Now I am searching for a good rust remover for construction (TMT) steel rods . I thought hydrochloric acid is best to remove rust. But if Hcl weakens the steel , what are the alternative ways to remove the rust??? Please give a solution for my problem... 🙏

[@dimmacommunication]

@@praja7491 Rust converter works best imho , works amazing. Citric acid works well if you want to clean small parts , I submerge them in a warm citric acid solution and in 2 hours they are ready 👌👌👌 I keep the solution warm with an electric heater

[@praja7491]

@@dimmacommunication 👍 I will definitely try it... Thank you... 🙏

[@KapiteinKrentebol]

You should get hold of Xenomorph blood. Very interesting video by the way, I betted on sulphuric acid but I'm impressed by the result of hydrochloric acid. Makes me wonder that if I swallow rusted screws if I will poop them rustfree.

[@nowonmetube]

Dot Matrix sure you would 😂😂 But then you might die (or get very sick) of the iron overdose.

[@harshsawant1416]

Thanks a lot. Can someone please help me with a few doubts. Is there any relationship i can draw from using different organic acids? And most importantly can i please know the name of this method? Name of scientific process or methodology used? Please I need it for my research paper.

[@antigen4]

i think the nitric acid was allowing the rust to break off in chunks because the nitric acid was attacking the iron below directly (?)

[@mrdavidurquhart]

Is there a point at which the Hydrochloric acid would start to eat the iron/steel? Did you forget to measure the dimensions of the metal pegs after the acid had worked on them?

[@BenNorway]

Within 20-30 min no eating of the iron will occur but if you leave the nails in the acid for 1-2 weeks, then the acid will start working it’s way into the iron along grain boundaries in the metal. This makes the metal iron brittle, also the process is referred to as hydrogen embrittlement. You will only be able to see this if you cut up the nail along the nails, which I have done. The short time I show on,h remove the dimension thickness of the rust. Thx for comment!

[@mrdavidurquhart]

Ben Norway wow that’s a fantastic answer. Thank you very much

[@herrar6595]

But wont the hcl break down the Iron at a similar rate too?

[@Ken_Sweden]

No that will happen much slower and via hydrogen diffusion into the iron , making it brittle.

[@herrar6595]

@@Ken_Sweden thanks man

[@firmbutton6485]

Ken, how about using HCA to get rid of most the rust, then rinse and the phosphoric to convert any that remains? Then rise, dry and prime before painting or waxing.

[@Ken_Sweden]

You mean the hydrochloride? If so, Yes I think that’s a good approach and you will avoid the flash rust

[@shacharnahari6009]

Nice experiment, a question - why did you use % concentration (all 30%) and not molarity (say for instance all 2M..). Would the results had been different if you use constant molarity?

[@Ken_Sweden]

I compared the vol% for simplicity. Comparing molarities would require me to roughly half the concentration of the hydrochloric since the rest end up on about 5-7 moles per liter, which on dissociation into ions will provide different number of moles hydronuim ions in the solutions as they would all completely dissociate at these pH. The active ‘rust dissolving power’ is however also affected by the nature of the counter ions po43-, cl-, so42-, no3- etc and the possible formation of soluble or insoluble byproducts at the surface of the rust. The phosphate may form some insoluble iron phosphate while the different forms of the soluble chloride ions are very corrosive in themselves. The released iron ions from the mixtures of fe2O3 (and iron hydroxides formed as intermediates) also need to be transported away from the surface upon the dissolution, which makes the action (liquid movements) going on at the surface also affect the outcome. Now, the presence of hydrogen and formation of gas at the iron surface is probably similar when the rust has allowed the pure iron to be exposed so I would guess the bubbles and movements of the liquid to be similar as the shape of the nails are the same, although it may take different times to expose the iron and we are not really pressure washing the nails with the different acids... So my honest answer is that I cannot safely state that the outcome would have been exactly the same if I used half the concentration of hydrochloric acid and compared that with the same as used concentration of phosphoric acid, while heavily shaking the nails in a plastic reaction vessel. However, I guess is that hydrochloride acid will still be the most effective, even using half in concentration while the others may line up differently.

[@gerdelyi]

Question.....Seeing that Phosphoric acid works best in that it doesn't allow further rust to occur immediately, and leaves a surface that inhibits rust, what happens if you use a higher concentrate? 75% Phosphoric Acid for example? Looking for an efficient way to clean my anchor chain.

[@Ken_Sweden]

+Gabriel Erdelyi To be honest you won’t see much difference since the iron reacting with the phosphate will be full converted also with the 30% you see in the video. It’s always very much excess of phosphate to rust in the acid. It may go a bit faster but you would really have to time it to notice the difference. For your anchor chain you may have an issue because the iron phosphate forming is like a porous layer, a good paint base coat, but with limited mechanical strength. Not to be negative but I would guess the chances it wears off are quite significant. I hope this helps and all the best!

[@Tokentools-weldersAu]

Hi Ken, thanks for the video. Did the phosphoric acid convert the rust to black oxide Fe3O4 like the rust converters do?

[@Ken_Sweden]

Yes but since it was in solution it appears as most of the black iron phosphate formed as a powder that easily was rinsed of with water. Thx for input!

[@Larry-d3i]

In the 1980's I went to work for a small chemical company as a development chemist and trouble shooter. The boss was not a chemist, but he had been there a long time. When I told him I could predict the outcome of certain processes by the pKa numbers, he said do you really believe that shit? He shut up when what I said would happen did happen.

[@zaiwanhassan1924]

Acid number one is hydrochloric acid???

[@50LOT1]

Ken thanks for this video. I am interested to know if I can make the aluminum anticorrosion by using cerium oxide ceo2? let me know if you have done that.

[@Ken_Sweden]

Google conversion coating and Mil en.m.wikipedia.org/wiki/MIL-DTL-5541. 🙏

[@rksando1]

Great video. Just what I needed before removing rust for a project.

[@noanyobiseniss7462]

Isn't the Phosphoric acid supposed to bond with the rust to form another compound?

[@Ken_Sweden]

+Noan YoBiseniss You are right, phosphorus acid reacts w released iron ions, and a black layer will form on your piece. However that has to be dried if you wish to keep it as a solid, perhaps prime for painting. I rinsed it off and only focused on the acids ability to dissolve the rust. Thanks again for your input!

[@delatroy]

Thanks a lot. Any advice for how to remove rust on a large scale like a farm shed please?

[@Dino_Buk]

HCL is the best. Just clean it well with the water.

[@delatroy]

@@Dino_Buk will the water contaminate the soil though?

[@Ken_Sweden]

For the most heavy rust, spray it with a diluted hydrochloric acid in open atmosphere, let it sit for some time and redo if necessary. Then rinse of with water and do a final spray with phosphoric acid diluted so much (10-20%) that it only bonds up with the surface and forms a iron phosphate cover layer that is somewhat black. This is a porous cover to that can be mechanically polished to the metal but many professionals see it as an excellent primer for having a paint layer out and effectively bonded to the surface.

[@elviskingiri3520]

What combination of chemicals is used to remove water marks from car windows

[@Ken_Sweden]

Citric acid is a good choice or even better limonene based solvents.

[@zibobpompon5768]

Excellent merci pour ces précieuses informations !!!

[@peterlee9933]

Such a well presented and useful video. Thanks

[@stephanelsner9391]

Great video, but I miss citric acid

[@JP-wx6uh]

Did you say the acids were all diluted down to 30% concentration? I couldn't understand if you said 3 or 30 percent.

[@Ken_Sweden]

Yes 30 % of their max concentration on their bottles

[@JP-wx6uh]

@@Ken_Sweden I'm trying to find the best solvent or acid to use for cleaning sampling tools that our department uses for asbestos sampling. We use chissels, needle-nosed pliers, screwdrivers, core samplers, etc. The tools are all metals (alloys). The materials that make the most problems with our tools are often very sticky, usually polymers such as adhesives under floor tile. I have been using 99% Methanol but I'm not sure if it is the best thing to use. I usually soak the tools for 20-30 minutes and then try to wash them off and buff them dry with hand towels. Do you think Acetone may work better?

[@douglasthompson2740]

Hello, I would have liked to see Muriatic acid included. It is easily available here in the US. Used to clean concrete and masonry as well as for swimming pools. Very interesting. Take care. Doug

[@Ken_Sweden]

Muriatic acid same thing as hydrochloric acid 👍

[@MG-nz6bx]

Douglas Thompson hydrochloric acid IS muriatic acid.

[@miialamia1653]

Note that muriatic acid, as it is sold, is usually of poorer quality (dirtier; as in containing more impurities) than when sold as "hydrochloric acid". All in all hardware store chemicals are cheap but usually not very pure by lab standards. May not matter at all for some uses (such as this), but may matter a lot for others.

[@sherannaidoo2712]

Why no tannic acid mate?

[@robertmendick3195]

A very effective product called Iron Out Powder is sold in hardware stores in the US. It is available outside the US on Amazon. The Iron Out brand also sells several other products which are liquids. The liquids contain different chemicals than what the powder has. Their very effective powder product contains sodium hydrosulfite, sodium metabisulfite, sodium carbonate, and propylene glycol. The only complaint is the strong sulfur smell as it works. Use with adequate ventilation.

[@Ken_Sweden]

Thanks for the info!

[@circle4922]

Hi, We were wondering why you didn't try tannic acid? Thanks.

[@Ken_Sweden]

+Complex it is too slow, it needs one of the acids in the video to perform. Good input, will get back to this 👍

[@circle4922]

@@Ken_Sweden The "industrial" ones (tannic acid products) I tried, one or two of them, work very well to convert the rust to a stable, black finish as well as a providing a protective layer on top (there's some type of polymer in the product as well as the tannic acid). One was called "Metal Medic" I think. From what I remember, it didn't take more than a couple hours to covert whatever it touched to a deep purple, and then black surface finish. Ok cool, Thanks.

[@Ken_Sweden]

Complex you are absolutely right about this and I’ve just a few month ago bought 1 kg (2lb) of tannic acid from a Chinese guy. I’m about to break up the formulas on what’s in these rust converters. They are very effective but often combined with phosphoric acids (in the video) to speed up the process. The main benefit as far as I’ve found is that the tannic acid molecule is big so it’s almost like the molecules in paint so when they bond the iron from the rust then the iron is bonded up in something that is far more durable, less crisp and fragile than the iron phosphate you get from normal rust eaters only containing phosphoric acid. The biggest limitation I’ve found is that when I scrape on tannic acid converted rust that is thick, I find rust underneath so the quality of the rust converters is in my view mostly real taped to their penetration depth. Thanks for raising this topic, it’s on its way. Just want to read a bit more on how to fix the assisting acids for increased penetration depth. Then I will be back with a make iT yourself recipe. Have a great day!

[@jiyavulhuk1859]

Sir ,Waste motor oil bleaching chemical name tell me sir. Please

[@rikujkoivisto]

Hi! Some says, phosphoric acid NEED water, to be more effective.. Many rust removers contains phosphoric acid. Sorry my english..

[@Ken_Sweden]

I think that's because concentrated phosphoric acid is very viscous as undiluted. For the acid to function it needs of course to release the iron atoms into ions from the rust but also transport the dissolved liberated ions away from the rusty surface. Now in the case that the transportation away from the surface doesn't work, it will end up as a volumetric zone that wont have the same low pka acidic value, acting as a weaker acid, and therefore not work as good. I am not 100% certain about this but it's a suggestion off the hip, knowing that boundary conditions often have effect on diffusion. Many thx for your comment. With a reference to your comment, I would better be able to answer.

[@rikujkoivisto]

@@Ken_Sweden Hi Ken! I think, i know what you saying. I have very rusty rims, and now, going to add some water in my acid, thank you very much, and God bless..! 😊

[@Ken_Sweden]

@@rikujkoivisto just do : acid ADD to Water. That's the rule Number 1. Good luck

[@rikujkoivisto]

@@Ken_Sweden Order was not the point, but thank you anyway!

[@docmadhattan]

@@Ken_Sweden Some people have to learn the hard way. 🤭

[@nowonmetube]

13:34 so in conclusion: if you have rusty nails, you should swallow them, if you want to remove the rust.

[@artlabuae7303]

Thank you for the great efforts. Respects from Dubai

[@Ken_Sweden]

Thx!

[@itssagnikstime3700]

If you aqua regia the rust will dissolve in few minutes in the solution

[@Ken_Sweden]

I will try this as a separate experiment. Thx for comment

[@ChristopherMaier.]

What about oxalic acid?

[@Ken_Sweden]

Oxalis acid 👍

[@johnnyheckard7185]

What acid would you recommend to flush a aluminum heater core on a car with and at what %?

[@Ken_Sweden]

I would go very very weak acid because the thinner aluminum sections are so fragile. I actually did my radiator on my car and to avoid having any issues, considering that it was the first time, I bought one acid cleaner by the name Holts Speedflush radiator cleaner. This product contained some acid and did a very good job, judging from what came out, while the acid still was so weak that I could poor it on my hands. Having said this, if you force me to take any acids, I would pickle the weakest ones like oxalic or acetic, or citric, dilute them to 20% and then try them on aluminum foil from your kitchen. You shouldn’t see any immediate reaction, only after perhaps 3-5 minutes. If the acid is too strong you will see it fizzing. Now, even if you take one of them oxalic, acetic or citric , and you have done what I suggest , then if you have a hole in heater core or in a radiator, then you know that hole was there all the time, ...only plugged up with dirt.

[@chrispompano]

Try TIDE powerdred laundry detergent 1st........! Also CASCADE "Fryer Boil Out" which is concentrted phosphorus cleaner that has been taken out of ALL dishwasher/laundry detergents due to enviro reasons, but that's what got dishes and clothes clean. If you decide to use any acid, be sure to neutralize it with a solution of Arm Hammer Washing Soda. Another old school way was to use the old Spic N Span cleaner. All of these cleaners had high phosporus, that you can still buy as the "CASCADE FRYER BOIL-OUT" Available on Amazon, and I still use a few TBS in my dishwasher with the detergents.... Years ago, GM had a private label from Prestone which was a 2 part powerdered radiator clenaer in can that opened on both ends made by by Prestone back in the 60's - 80's, but can be easily dupicated with wood bleach (Oxalic Acid) and Washing Soda for the netralizer. Research : "Prestone and GM cooling system cleaners oxalic acid. ... the Prestone Heavy Duty Cooling System Cleaner P/N AS100 (GM P/N 12346500)". Long discontinued, but I think it was 6oz Oxalic Acid Powerder, and 5oz Washing Soda....it doesn't have to be precise mix.... Also there are organic acid Marine heat exchange cleaners on the market that are very safe but need to be run for a few days and will only remove the scale and not metal. Ryd Lyme is the famous brand. Not sure if it's aluminum safe or not. Also look up the GM TSB for that old Prestone AS100 cleaner....lots of info in the forums of the DexCool Sludge Flush problems. Follow GM TSB 99-06-02-012D for DexCool sludge problems....

[@johnnyheckard7185]

@@chrispompano Lots of info here appreciate the time and the effort you put in here I will look into that technical service bulletin and again thank you.

[@chrispompano]

@@johnnyheckard7185 Your welcome. The Cascade dishwater det. trick really cleaned cooling systems, but may not de-scale them. The gentle way was using a citric acid that most radiator cleaners contain, but are too weak in formulation in the products at the auto-parts stores. I also posted this below: There's a very safe HCL (Muratic Acid) that's buffered, but still full strength at 31% called "ACID MAGIC" by Certol. www.certol.com/acidmagichome/ Maybe dilute that down....... Another formulation is TSP (Tri Sodium Phosphate) which is in the CASCADE FRYER BOIL OUT to also try before graduating into full-acids.....but all these radiator flushes with those cleaners are just that.....cleaners to remove grease sludge not to dissolve calcium deposits. If you end-up with holes in the core, or your entire system, all those new generation block-sealers are the way to go to seal things up ......but some need to have the system flushed and free of all anti-freeze or you'll run into problems...KW has a very good formulation of the one you circulate then wait for the system to cool, drain, and open the system to air-dry, and they and other brands have leave-in formula's which use kevlar to plug holes which far surpassed the old technology of the Stop Leak Tabs used by GM which was wood-pulp...... IRONTITE is a unique ceramic block sealer also in case you end up with leaks everywhere....

[@juliusvalentinas]

how to make phosphoric acid or any other to a gel you can brush on?

[@bigrockets]

you cannot practically make phosphoric acid at home, it takes specialized lab equipment and chemicals to produce it. you have to have some sort of chemistry background to make this stuff, it ain't like baking a cake. Duda Diesel sells 85% food grade phosphoric acid in quarts and gallons. It's reasonably priced, they are a reputable company to deal with, as I have purchased that chemical from them before. 85% phosphoric acid can be dangerous if handled carelessly? You need lab gloves, full face protection and you should also use a respirator, just to be safe. At this concentration a 10% solution or even lower perhaps is all that's needed to remove rust . Like a couple of ounces into a bottle full of water in an old Windex bottle is what I use. FYI.

[@juliusvalentinas]

@@bigrockets I was asking how to make phosphoric acid I already have into gel to brush it on large parts like a car?

[@Ken_Sweden]

+juliusvalentinas I’m working on it.... now

[@juliusvalentinas]

@@Ken_Sweden Thank you for reply. Hope it all works out.

[@qbukhari]

Make a paste of sodium carbonate with water and rub it all over rusted iron Dip the iron in HCL , now due to chemical reaction with sodium carbonate, hcl will remove rust in minutes. Neutralize the iron in mixture of water and sodium carbonate. Apply some oil on iron to prevent rust.

[@WeldersforJesus]

Can you store hydrochloric acid after it is used for rust removal? At what point does the reaction stop creating hydrogen and can I cap it in a class container afterwards?

[@WeldersforJesus]

*glass container

[@Calendyr]

Would have liked to see how Hydrofluoric acid and Citric acid did. I usually use vinegar or wheel acid (hydrofluoric) to remove rust on steel parts and it works in minutes. Never had to deal with heavily rusted iron like you did.

[@bigrockets]

hydroflouric acid is a weak acid, it's kpa is lower on that scale of strength than is H2SO4, HNO3, HCL and the other 7 strong acids. It has a very significant health risk in using it. Even small amounts spilled onto skin or even clothing in contact with the skin can be deadly . Phosphoric acid is safer to use and produces superior results. Lots of folks don't know about HF'S quiet demon inside. Seems the flourine atoms due to their extreme electronegativity have an affinity for calcium ions in the body and replace them with their own fluorine ions that produces necrosis of the bones and liver malfunctions. Just some info for you brother, tryin to just keep us safe is all.

[@integralfrom0to1]

@@bigrockets also messes up the calcium that tells your heart what to do, which tends to be a problem

[@TerraceBalloonMan]

Video played all the way through.

[@wingrider1004]

I use electrolysis and would prefer vinegar over any real acid simply for ease of disposal and safety. Thinking about a muriatic acid accident gives me nightmares. I'll work a little harder and stress a little less. They all have their applications.

[@idontknowmyfirstname69]

Some of those acids are still too strong... You're getting an oxide passivation layer on the surface of the iron... Essentially you're giving it an insoluble layer of skin on the surface

[@papaya_virus]

Great review. I used Phosphoric several times on rusted bike tanks and works great. It's very slow but leaving a week leaves a zinc/mercury colour layer, protecting the part. But next times i'll first use hydrocloric (cheaper at spain) and save my phosphoric for detailing :) In past I also tried rust cleaners that looks opposite reaction, like caustic (orange liquid). What's the best form for treat/close the pore of the metal after de-rust it? (for naval/yatching uses) (appart bicomponent painting)

[@Ken_Sweden]

+ΓΛBIПθΓθJθ ...the best to do for Naval if its porous is to zinc plate it by using reverse electrolysis. That way you will have a thin layer of zinc sacrificing metal covering your part all the way into the pores. On top of it you do a conversion coating, then prime and top coat. Maybe a bit complicated so lots of folks buy the hazardous chromate primers directly for their aluminum parts, and top coat to seal the primer as good as possible. For conversion coatings, there are a couple on YT. Good luck!

[@papaya_virus]

Thanks for the reply, I'll search about everything you wrote here. And without using reverse electrolysis? It's for heal an 9 meter boat keel, it's iron foundry (not inox steel or mercury). After I have plans to electrically catodize it with a cable from the battery but for proper re-rust.. wich steps would be better? I was thinking in 1) grinder cleaning most until reach the healty iron. 2) hcl acid with brust 3)shave 4) rust converter 5) primer ...

[@Bodragon]

What about tannic acid ? Tannic acid is used in quite a lot of commercially available rust converter preparations. >

[@Stan_in_Shelton_WA]

what about acid blends? I do not remember what mix I used many years ago, either sulfuric and nitric or nitric and hydrochloric and it removed the rust and some of the metal very very fast. Acid blends like for gold, aqua regia, are not some crazy idea nd they work great.

[@nowonmetube]

Stan Rodgers yeah that would take even some more effort to try out all the blends...

[@MrZnarffy]

Still, it might be good for one thing only, and not other.. HCl still beats aqua regia for iron. However it also eats pure iron. To selectively remove rust but not iron, you need to look into things like absorbtion spectra and use tuned lasers, which are extremely quick in comparison.

[@nautitard]

We have very expensive bottles of phoshoric acid here where I live and it's 8 € for a ridiculous amount that would suffice if you want to derust a few bolts or an axe head, but for a whole undercarriage, it's just stupid. I bought 1 litre of hydrochloric acid today for 8 €, which is 30 % and will be diluted and then mixed with tapestry glue. This will be brushed on the undercarriage, then rinsed thoughrougly with high pressure water, dried with a bicarbonate water soaked rag and then dried with heatgun. Directly after that I will paint with epoxi primer. I think this should work and the disadvantages of hydrochloric acid compared to phosporic shouldn't be that big if you paint straight away?

[@Ken_Sweden]

The hydrochloric is killing the rust like no other acid but it seems to want to come back so check out my last video, just today, on how I do it. The phosphoric also lets a small amount of red dish come back but then I get it with the tannic acid. What I don’t say in the new video is that the tannic acid makes a fascinating surface that you see as only matt black in the video but in reality, if you zoom in on this surface, it’s like smooth and soft feeling when dried. I have had very good experience with this surface, every time, regardless what I paint, it always suck up the paint and levels the paint very evenly. Then the paint sits rock hard, of course best for epoxy, and even better for powder coated epoxy, I’m just amazed myself. It doesn’t matter which tannic acid you use, or rust converter, but it has to be that tannic acid... I have tried several brands and no difference, some are more yellowish. Just one this more, you see that your tannic acid is active when you brush it on, and for a split second your surface show as purple in color, very strange but that is always the same, then with more layers it becomes black as in the videos.

[@cpayne1757]

So great video but do you know of any commercial products that has hydrochloric acid content that is safe to use for automotive rust??

[@Ken_Sweden]

I think the producers are staying away from hydro chloric acid mainly because of the possibility to have residual chloride ions that if nor eliminated will induce more rust to form.

[@chris532008]

Zippy DoDah coat before dark let night humidity keep active for hours. Use pump sprayer next evening to reactivity next night

[@jjenson2006]

surprised you didn't include Oxalic acid.

[@chris532008]

jjenson2006 very weak

[@jjenson2006]

No it's not. It's stronger than half the acids tested here. It's Pka value is 1.23

[@Ken_Sweden]

+jjenson2006 Oxalic acid comes in before phosphorus acid, it is a little bit better at dissolving rust than phosphorus. Pka value 1.46. However its a much poorer performer than Hydrochloric, sulphuric and nitric acid. Thanks for input!

[@kimberleybarrass6531]

For auto work I've found oxalic to be the best... It doesn't seem to attack the metal as much and doesn't seem to flash rust... I rub it in with aluminium sheeting though, which might be what helps.. :(

[@robertmendick3195]

I had very good results with oxalic acid. In the US it can be found in the paint section of hardware stores and is called Wood Bleach.

[@danielberei3021]

There is one problem with your experiment. For ex. phosphoric acid works best when not dipped into it, just sprayed over.

[@hendrikabbeloos8420]

Yep, it interacts with air(O + N) just like rust removers turn from pale to dark when the P-acid eats the oxides.

[@docmadhattan]

What's the ideal concentration that works best? One that works better from the more diluted rust converters?

[@danielberei3021]

From experience I can say it depends on metal, temperature, etc.

[@docmadhattan]

@@danielberei3021 I'm guessing the cooler it is, the higher the concentration, and vice versa? Thanks

[@danielberei3021]

Well I haven't thought of that, but a higher temperature makes things faster I guess. Higher concentration doesn't always work. Some steels get a superb grey finish, the rust is easily removed on some, and others you can scrub all day and rust will still be there in a black layer(mostly on mild steels). If it's a black layer, it's paintable and it will last I can assure you that it won't flake. Done several car underbodies and painted them with hammerite garage door. It will last for yonks

[@mrrmsfucker146]

Muriatic acid?

[@Ken_Sweden]

Same as hydrochloric

[@migmadmarine]

railroad spikes seem to be popular for these tests.

[@Ken_Sweden]

+migmadmarine hahha, certainly they are. Only hardcore testing here. If you induce rusting, which some folks do in KZbin videos to show the results, then the rust has formed very fast and is not the same as genuine more sold rust forming over long time. I’ve tried the fast rust, works excellent and you get it by just pouring some acid on the iron and leave outside for a week. It looks like a disaster, but the rust is so weak and porous that you can scrape it off. Wouldn’t be a true test to show... so I hit the old railroad tracks with loads of ‘true rust’. Good comment!