Rust Removal Methods Explained

I get quite a few questions about removing rust there are a lot of different recipes out there from coca-cola to hydrochloric acid there are a lot of different liquid methods it's really not that complicated I'm going to attempt to summarize the common liquid methods into one short video this involves science scientists please stop watching the video now I'm going to get into this just enough to help out other guys like myself playing around in the shed to understand what some of the options are if they work and what chemicals you're playing with as a result phosphoric acid and nearly all of the commercially available rust treatment products convert rust into an inert fine oxide these are unsuitable if you're after a beer metal finish for parts that will subsequently be painted I like phosphoric acid electrolysis a bit of a pain to set up but if you can deal with the hassle electrolysis is the best cheap rust removal method the best expensive rust removal method is evapo rust then we have the acids vinegar citric acid oxalic acid and hydrochloric acid most of the magical rust removal recipes you'll see on the internet are based on products containing one of these acids all of these assets will remove rust and all of them will corrode steel but you probably only have to worry about that with hydrochloric acid for you guys looking for the easy cheap DIY option I suggest citric acid let's start with vinegar the Internet's favorite rust remover vinegar is mildly acidic and will remove rust vinegar sets at about 3 on the pH scale vinegar is mostly water with about 5 to 10 percent acetic acid it's the acetic acid that removes rust I'll only be showing the effect on iron oxide with 3 oxygen molecules which is common brown rust and acetic acid two carbons four hydrogen's and a couple of oxygens don't pay any attention to the arrangement of molecules in this video that's just me stacking them up for this equation to balance out we need six acetic acids but that won't fit on the screen so we'll pretend it works with two so what happens is that the acetic acid pulls the iron out of the rust this bumps to hydrogen and our new element is ferric acetate a yellowy Brown liquid that leaves a couple of hydrogen's and an oxygen two hydrogens and an O is water half a day is how long I'm leaving the parts and the weaker acids I'm not interested in waiting a week to remove rust vinegar is very weak and not at all hazardous it costs about $3 per liter on rust that's an effective there are cheaper methods that work much faster technically vinegar will corrode good steel but not to any noticeable extent in any reasonable timeframe just to be fair to those perpetuating the vinegar method I lift the nut and overnight plus another full day and this is what it looks like citric acid you may have seen me using citric acid in a few videos I like it because it's cheap I tend to use it on items like tall steel may be covered in a tarnish of rust the acid is strong enough that it works but mild enough not to cause any problems if you leave something soaking for the day I don't pay any attention to a mixture ratio just mix some dry citric acid with water oxygen comes out of the rust and teams up with a couple of hydrogen's to form water that leaves us with two parts iron oxide this is a black inert iron oxide that will typically break away from the part when the rust breaks down the carbon and oxygen becomes carbon monoxide the remaining oxygen becomes water and the hydrogen becomes hydrogen just like vinegar I lift the nut and citric acid for about five hours citric acid is very mild and safe to use you can buy it from the baking aisle of the supermarket and small quantities but that's a pretty expensive way to get it I buy mine from a bulk burn store for about seven New Zealand dollars per kg it's moderately effective depending on the part I wouldn't use it to try and get rust out of deeper pitting citric acid will corrode good metal but I've never noticed any adverse effects I think it would take days to see any real effect on still oxalic acid is a fairly strong acid a little harder to find than the other acids though I did purchase this from Bunnings oxalic acid is naturally occurring in many vegetables the idea of using molasses as a rust remover has become popularized on YouTube there's nothing miraculous going on molasses just contains traces of oxalic acid equally you could remove rust by soaking parts and broccoli mesh while stuffing them inside a potato oxalic acid to hydrogen's to carbons and four oxygens we need six oxalic acids for the reaction to balance the iron is pulled out of the iron oxide and binds to the oxalic acid the hydrogen's team up with oxygen to form water that leaves us with Pyrrhic oxalate that's the yellow liquid I left the nut and the acid for about five hours oxalic acid is fairly strong try to refrain from splashing it all over yourself this 500 gram bag cost about 18 dollars the packet is marketed as a stain remover for timber and and that use the packet says the mix will make 5 liters as you can see it's removed most of the rust definitely more than citric acid oxalic acid is not going to cause any noticeable corrosion on your goods steel within a reasonable timeframe evapo rust is not an acid it is near enough pH neutral it removes rust through a process called chelation chelation is when a chemical binds to a specific element in this case iron and pulls that element into a soluble state the exact ingredients involved aren't published on the bottle but this is approximately what's going on evapo rust is manufactured to not be able to pull iron out of steel that will however pull iron out of rust I don't know what happens to the oxygen the second part of evapo rust pulls the iron out of the first discarding it this leaves the first part free to start all over again in theory evapo rust lasts indefinitely and reality there are inefficiencies and it will stop working after a while I left the nut stoking for about five hours I wouldn't trust that evapo rust as non hazardous I bet the ingredients list reads like a chemists dictionary but it's not an acid so you don't have to worry about it in that sense evapo rust as expensive too expensive for me i bought the small bottle for the sake of this video but i doubt i'll be buying enough to use for any large parts it will not corrode good steel at all that's why if you can pay for evapo rust it's a much better option than any acid now for something a little more fun and by fun I mean burn your skin off hydrochloric acid is by far the quickest method in this video for annihilating rust but it's not what you want to be using in most cases depending on the concentration hydrochloric acid sits on the pH scale somewhere between 0.1 and one the stuff you get from the hardware store is going to be closer to 1 for this video I'm using acid straight from the bottle normally I would dilute it at least half with water so we have rust and hydrochloric acid one hydrogen and one chlorine or chloride in this case for this reaction to balance we need 6 hydrochloric s' the essent pulls the iron out of iron oxide and formed spheric chloride that's the yellow liquid the hydrogen teams up with the oxygen to form water that's a perfect reaction with iron oxide ferric chloride and water but of course the acid is also reacting with the iron and the steel so basically if we take away the oxygen we still get ferric chloride but we ended up with hydrogen gas instead of water that's what all the bubbling is bubbles equals your good Steel disappearing then that was in the acid for something like 3 minutes as it hazardous yes at this concentration if hydrochloric acid comes into contact with skin it will burn the vapor is also nasty and corrosive don't use hydrochloric acid inside or anywhere near metal objects I think a 4 liter bottle costs about $20 hydrochloric acid is about as good as it gets for a moving rust the downside is that it leaves the surface of Steel in an act of itched state which makes it very prone to rust it'll also ruin threads and find details in a short space of time because it itches surface hydrochloric acid is widely used as a preparation for electroplating and galvanizing and that's what I use it for a quick adapt of prior to electroplating the next two options are different from the rest and that they convert rust rather than dissolve it there are a huge number of these converters available and they're all pretty much the same this one is based on tannic acid some are based on phosphoric acid all with the idea of converting iron oxide into an inert black oxide the basic chemicals that do the conversion are well proven the difference between all of these products is the other fluff they put in them some of them are formulated into a gel some of them hardened to a layer of clear finish some of them claimed that the annuity oxide they create is a magical black primer this particular brand contains a binder that sits into a clear hard coating I stress this to point out the difference between using these products compared to straight phosphoric acid do you really want that $10 bottle of rust converter to provide a primer layer under a $10,000 paint job this converter is based on tannic acid I'm not going to model that out on screen because the formula has way too many numbers attached depending on the specific product there's no reason that these converters shouldn't convert 100% of the rust they come into contact with the problem with this particular product is that the clear binder sets so fast that the tannic acid has very little time to soak into rust before it hardens the conversion happens almost instantly if the product is very weak as it will take longer and if the product is trying to be a paint system as well you'll obviously have to wait for that to cure this one liter bottle cost $26 so I've presented a feeling negative case for these converters but I actually use this particular product all the time for exactly what you're seeing here a quick method to blacken and seal rusty nuts in bolts phosphoric acid is a rust converter this bottle is labeled rust kill but it's just phosphoric acid phosphoric acid is fairly strong it's the magic ingredient in coca-cola good for your teeth the phosphoric acid comes into contact with rust and converts it into a ferric phosphate this will either fall away from the part or if it is tightly bound to the steel stay on the part there's an obvious black mark the hydrogen teams up with the oxygen to become water in theory the conversion happens the instant the acid comes into contact with iron oxide but I normally brush it on and then leave it for a good half-hour to soak in it is fairly hazardous nowhere near as bad as hydrochloric acid but it is the next worse in this video this 1 litre bottle was $18 it is effective on light rust I haven't used it in the context of dealing with heavy scaling that's where the angle grinder and well that comes out phosphoric acid is best used as one part of the prep process and dealing with panel steel on vehicles and other similar situations phosphoric acid will definitely corrode steel if you're just brushing it on that's not something to worry about finally electrolysis assuming you already have some sort of power supply a glass jar and a couple of bits of steel this is the cheapest method of rust removal there are some extra set up time compared to the other methods and the part will need scrubbing afterwards what you'll need is a container of some sort plastic or glass an old cell phone charger or any other low current power supply a strip of Steel this will be the anode an extra piece or two will allow you to spread the current out around the container but it's not necessary the jar will be filled with water tap water before I filled the jar with water you saw me aired washing soda sodium carbonate this is what you'll see everyone used for electrolysis but I want to point out that sodium carbonate plays no part in the rust removal process it's only role is to increase the conductivity of the water I think this will work fine with just water though it'll take longer with the equivalent amperage alternatively you could also increase the conductivity with a spoonful of table salt but that will give off chlorine gas unless you're huffing the jar I doubt that'll be an issue but I suggest just use washing soda like everyone else it's only cost a couple of dollars so there are two separate processes going on the first is electrolysis the second is the rust removal if we pass a current through water guesses generated at either pole at the positive pole or anode oxygen is produced and at the negative pole or cathode hydrogen gas has given off that's electrolysis now the second part is rust removal this is a reaction between the hydrogen and any oxygen contained in the cathode the big mass of ions represents our steel part the hydrogen pulls the oxygen out of the iron oxide mostly the rust will break apart and the iron from the iron oxide will fall away it's possible that if the rust is tightly bound that the hydrogen will pull the oxygen out and the iron will stay in place thus we've actually recovered iron oxide back into the Part D rusting this nut took about two hours but that will vary depending on the size of your part and the amperage this isn't hazardous you could give yourself a shock I guess hydrogen is flammable and technically there is a risk of explosion but at the scale I doubt we're going to get anywhere near the concentration of hydrogen gas needed to cause an explosion that's cheap assuming you have all of the equipment around the house it cost next to nothing let's say three dollars for the sodium carbonate it is very effective at removing rust the only other method that works as well as evapo rust the biggest downside of this method the part is covered in black gunk afterwards that you will need to remove with a wire brush electrolysis will not harm your steel part at all for small parts electrolysis as my preferred method of rust removal sometimes an acid is more convenient and evapo rust works just as well if you can afford it in summary all of these methods are worth trying but if I can get away with it there's still only one best method you

Channel: Geoffrey Croker

Views: 1,063,261

Keywords: rust removal, vinegar rust, electrolysis, citric acid, hydrochloric acid, phosphoric acid, molasses

Id: Qi-tK1jwO-k

Length: 19min 15sec (1155 seconds)

Published: Mon Dec 04 2017