Home made "Evaporust" formula

[Screwdriver]

So for just a citric acid solution whats the shelf life like, how long does it last?

That's a good question and one I have been asking myself. Leave a citric acid solution in the shed or outside and it will blossom into a veritable forest of biological activity. Fungus and moulds I should expect. Citric acid is a very concentrated food source! We all know what a used coffee cup looks like if you leave it in the shed (it's the sugar that does it) and a cup of citric would do that too.

In the house where I keep a few sealed jars of citric, It keeps for weeks/months. Needs to be kept out of direct sunlight since, as its an organic solution, it will UV degrade.

So I am also wondering what this particular solution will do if exposed to the elements. I'll leave a jar of it outside alongside maybe a ajar of pure citric as a control sample.

Almost forgot, this was after one hour.

I had to hammer the pin out. Stuck it back in the dip. I think these things are plain mild steel and the rot is excessive rusting. Left them too long in the shed.

 

[rcx132]

So for the thick people like me whats going to be the difference between this and straight citric acid/water mix??

It's a different chemical reaction that doesn't require strong acid.

 

[julianf]

Presumably then, the relative concentration must be key in producing a "working" formula.

No doubt at all that this concoction does indeed work.

Whether or not it is "Evaporust"...

It's not like the salts etc vanish then - there will still be "stuff", but if you neutralize all the proton donors then there won't be any proton donors any more.

That's not to say it doesn't work. Just that there won't be acid left if you neutralize it all.

 

[Screwdriver]

It's not like the salts etc vanish then - there will still be "stuff", but if you neutralize all the proton donors then there won't be any proton donors any more.

That's not to say it doesn't work. Just that there won't be acid left if you neutralize it all.

Chemistry is not my bag so when it comes to molar weights and PH etc, I'm out. I think the solution is not neutralised completely but forms a chelating agent. Wiki suggests this solution can then "go after" a specific type of metallic bond depending on its place in the reactivity table. So a chelation can form a bond with iron oxide but not pure iron or steel alloy or at least not so vigorously.

Anyway, all I know is, someone else has figured out the relative concentrations, it works. If it's anything like <the real thing> it will not degrade over time like pure citric will and can therefore be mixed up in huge batches and kept handy in a massive bucket.

 

[Jelly_Sheffield]

So for the thick people like me whats going to be the difference between this and straight citric acid/water mix??

He's effectively making a buffer solution, which will stay close to pH neutral (depending on what base you use, the pH changes), and will continually release a small amount of "free" citrate ions that can react with the iron oxide.

Reducing the free citrate concentration alters the balance between the rate of reaction for different possible reactions, which means it will preferentially attack the Fe+3 ions in iron oxide, whilst the reaction with the Fe(0) atoms in the steel slows down to almost nothing.

Based on the smell when it's been used, I suspect that real evaporust uses a quite complicated organic acid and base, selected to perfectly tune the reaction rates and electrochemistry that this is approximating.

I did something similar with EDTA a few years ago, which could be "refreshed" when spent by adding a precise dose of HCl (brick acid), but it was quite finniky, and if you added even a few ml too much acid, became quite corrosive to steel.

 

[Screwdriver]

Hmm, well that differs from my lay persons understanding. From what I gather, the acid forms a chelating agent and as @julianf suggests, the organic acid is converted into a sodium salt. So I guess that means the process by which such a solution works does not rely on the typical acid metal reaction.

Chat GPT tells me these sodium salts (in this case sodium citrate) bind to metal ions (rust!) which forms a water soluble complex "effectively chelating them".

I don't fully understand that of course but it does differ from your description above.

I could cut and paste the entire response but it's sort of irrelevant to the main thrust of this thread which is: does the concoction work better than pure citric for the reasons I state earlier. So if you want to deep dive (and I really don't!) you could just go ask ChatGPT yourself and let him, err, her, they (it?) thrash out the details.

I just want to dump some very rusty vices into a very large bucket without breaking the bank.

 

[Jelly_Sheffield]

Hmm, well that differs from my lay persons understanding. From what I gather, the acid forms a chelating agent and as @julianf suggests, the organic acid is converted into a sodium salt. So I guess that means the process by which such a solution works does not rely on the typical acid metal reaction.

The chemical mechanism by which the Fe(3+) ions are removed from the solid doesn't actually differ between using a "conventional" acid reagent, or a reagent that exhibits chelating behaviour.

Most chelating agents (of which citrate is one) are weak acids (i.e. they do not fully dissociate into ions when dissolved), which can be used either in the form of a free acid, or as a salt with a strong base which when dissolved in water will form a buffer solution.

Chat GPT tells me these sodium salts (in this case sodium citrate) bind to metal ions (rust!) which forms a water soluble complex "effectively chelating them".

I don't fully understand that of course but it does differ from your description above.

Chelation actually refers to a bonding mechanism between metal cations (+ve) and organic anions (-ve) in solution, which forms a "complex", rather than a salt, crucially, complexes are substantially less likely to disassociate into ions again.

That heavily biases the reversible electrochemical reactions at the solid-liquid interface one-way, which can have the effect of substantially increasing the rate of reaction.

Which explains why citrate works more effectively than many other acids at equivalent concentrations, and more generally why "chelating" rust removers are more effective in general.

Combining the Chelating/Complexing and Buffer behaviours allows us to formulate products with both a high rate of reaction, and a high level of selectivity to attack Fe(+3) thus removing rust without damaging base metal.

 

[Ross365]

Combining the Chelating/Complexing and Buffer behaviours allows us to formulate products with both a high rate of reaction, and a high level of selectivity to attack Fe(+3) thus removing rust without damaging base metal.

I suspect that for a commercial product like Evaporust, a good deal of time and effort has been spent on developing optimum formulations, and that is what you are paying for when you buy that product.

Is there an argument though, that for home use, citric acid solution, perhaps including a corrosion inhibitor (as discussed in other threads) is an adequate combination? I guess a lot depends on questions about how much dissolution of the metal you can tolerate and maybe other factors, so may depend on the particular job and user?

 

[Jelly_Sheffield]

I suspect that for a commercial product like Evaporust, a good deal of time and effort has been spent on developing optimum formulations, and that is what you are paying for when you buy that product.

Oh god yes, I suspect that a not insubstantial part of the price of Evaporust is recouping their R&D costs (and paying back the financing needed to make it through that process).

Is there an argument though, that for home use, citric acid solution, perhaps including a corrosion inhibitor (as discussed in other threads) is an adequate combination?

Yeah absolutely, I'm not advocating for one particular product (or even type of product chemistry), just trying to provide more information about how these formulations work.

I guess a lot depends on questions about how much dissolution of the metal you can tolerate and maybe other factors, so may depend on the particular job and user?

That's exactly it, there's a reason that some metalworking applications still use strong acids for rapid pickling, and why manufacturers choose HCl, HCl/Nitric, Sulphuric or even more exotic choices as their pickling acid.

Similarly with rust removal, there's the choice of several mechanical methods, strong acids, conversion treatment with Phosphoric Acid, various organic acids, or chelating type products (homebrew or otherwise).

FWIW, as someone who was originally a chemist by training, I would always advocate mechanical rust removal techniques as being the most efficient default approach...

Chemical removers can be the better choice for delicate or awkwardly shaped workpieces, but it's slow, messy, expensive and a lot of effort; even compared to shot/wet-blasting.

Where chemical removers or converter processes really come into their own is preparing rusty surfaces for coatings.

 

[Screwdriver]

I sincerely doubt there is a "magic" formula requiring super precise chemistry and in any event, for my purposes, neat citric acid is absolutely fine. Bung a rust lump of iron into a bath of citric and when it comes out, the rust is gone. If I was cleaning high precision parts or polished surfaces (or perhaps plated parts) then I might need to revise my thinking, in which case I might just go for electrolysis or some other process.

I don't feel the need for a corrosion inhibitor. If the acid is too strong, make a less concentrated solution or don't leave it in the bath so long. None of the household products we use are as magic as the incessant advertising and branding propaganda would have you believe. It is a science but it is not rocket science. Near enough is good enough. WD40 smells great but is little more than paraffin in a handy spray can. Evaporust is almost certainly derived from either citric or acetic acid as described in the original video that kicked this all off.

What does interest me is I have noticed my citric baths become a garden of mould and fungi in next to no time. A neutral solution is less biologically active. I also note the first test batch I made seemed to really clear off rust much more quickly than I have seen with citric. That and the fact that so many of the YouTubers I watch rave over Evaporust (and are probably paid handsomely to do so) makes this an interesting proposition. I **think** this type of dip might even be more friendly towards delicate coatings like nickel plate or passivate finishes - I will need to look that up or test a couple of samples first.

There is also the added bonus of being able to mix up a batch of a ridiculously expensive branded product for next to nothing. Like finding your favourite film on a pirate website in full HD. Have you seen how much Evaporust costs!! Even if it is a beautifully precise chemically engineered masterpiece, if this diy home brew mix is even only half as good, that's good enough for me.

So while I do find the technology behind the process of some interest, of more interest is the practical application. I might just work out the costs before knocking up a bathtub full of the stuff but it's going to be way less than £1/litre that's for sure.

 

[Jelly_Sheffield]

Evaporust is almost certainly derived from either citric or acetic acid as described in the original video that kicked this all off.

The patent explicitly states the composition:

• Ammonium Citrate,
•Sodium Phosphate,
•Sulphuric Acid,
•Sodium Lauryl Sulphate, and
•Sodium Benzoate.

It's a lot less advanced that I expected TBH (better is definitely possible), but it explains the smell perfectly, but they've clearly done a fair bit of formulation chemistry to get it to behave in a non-corrosive manner with those ingredients.

What does interest me is I have noticed my citric baths become a garden of mould and fungi in next to no time.

You could try adding a small amount of a quaternary ammonium salt, or another mild biocide like benzalkonium chloride.

The dose rate for effective microbial protection with both of those is surprisingly low, so a 100g bag would go a very long way.

 

[Ross365]

That's exactly it, there's a reason that some metalworking applications still use strong acids for rapid pickling, and why manufacturers choose HCl, HCl/Nitric, Sulphuric or even more exotic choices as their pickling acid.

I used to be involved in pickling stainless steel; we used a nice combination of hydrofluoric acid and nitric acid. We then passivated it with nitric alone. This two-step process leaves the steel with a relatively smooth and chromium-rich surface and had a big effect on making it more resistant to attack by strong oxidisers.

I see the rationale for sodium carbonate having the effect of mopping up hydrogen ions so getting more citrate ions in to solution; never occurred to me before. It is many decades since I last dabbled with buffer solutions . I only ever need to make up small quantities of citric and I don't keep it after use.

 

[Screwdriver]

The patent explicitly states the composition:

• Ammonium Citrate,
•Sodium Phosphate,
•Sulphuric Acid,
•Sodium Lauryl Sulphate, and
•Sodium Benzoate.

It's a lot less advanced that I expected TBH (better is definitely possible), but it explains the smell perfectly, but they've clearly done a fair bit of formulation chemistry to get it to behave in a non-corrosive manner with those ingredients.


You could try adding a small amount of a quaternary ammonium salt, or another mild biocide like benzalkonium chloride.

The dose rate for effective microbial protection with both of those is surprisingly low, so a 100g bag would go a very long way.

Wow. I had no idea there would be an online recipe! Then again, for my purposes, citric does pretty much everything I need so I've never looked. I am pleased to see I did guess correctly the use of SLS as a wetting agent which I happen to have on hand after trying to make up some Nitromors. That never did work like the real thing.

Since we're on a roll, I'm assuming Niromors is basically methylene chloride and the "trick" with it is to stop it from evaporating in seconds. I tried everything (methyl celluose etc.) to bulk it out to a gel and stop it disapearing, all to no avail.

So if there is a recipe for Nitromors I'm all ears. never found anything that is anything like as good for stripping paint.
And I just loved the smell!

 

[julianf]

Wow. I had no idea there would be an online recipe! Then again, for my purposes, citric does pretty much everything I need so I've never looked. I am pleased to see I did guess correctly the use of SLS as a wetting agent which I happen to have on hand after trying to make up some Nitromors. That never did work like the real thing.

Since we're on a roll, I'm assuming Niromors is basically methylene chloride and the "trick" with it is to stop it from evaporating in seconds. I tried everything (methyl celluose etc.) to bulk it out to a gel and stop it disapearing, all to no avail.

So if there is a recipe for Nitromors I'm all ears. never found anything that is anything like as good for stripping paint.
And I just loved the smell!

DMC used to be available on ebay (etc) but has now dissappeared.

It still seems to be in some commercial brews, but getting it straight seems impossible now.

I mention this as effort spent on homebrew DMC mixes may now be redundant : (

 

[bigegg]

Opinions on adding wallpaper paste to make a "paint-on" de-ruster?

 

[8ob]

Opinions on adding wallpaper paste to make a "paint-on" de-ruster?

Why not? Bit like using it with roundup on waxy leaves, without the paste it evaporates,dries out or runs off before it’s done it’s job.

Bob

 

[Seadog]

DMC used to be available on ebay (etc) but has now dissappeared.

It still seems to be in some commercial brews, but getting it straight seems impossible now.

I mention this as effort spent on homebrew DMC mixes may now be redundant : (

DCM is now available only on a commercial basis, under licence

 

[JOEPRO]

Opinions on adding wallpaper paste to make a "paint-on" de-ruster?

Vilt hamber already have a product per that spec.

 

[JOEPRO]

I would have to assume here that most posters to date have not actually used Evaporust!

It works much faster and better than Citric acid and does not require heat or anything.

I used evaporust on some Mercedes parts and was very impressed. Anything no matter how heavy the rust was came out totally rust free about 24 hours later. No agitating or heat required very simple. And those parts did not flash rust either even sitting for a couple of weeks in the garage. So I'd go as far to say there is a corrosion I hibititing finis on the part when fished out of the evaporust.

Citric acid does work but takes heat and maybe a week or so to de rust. And it's not as thorough as evaporust is. The parts can also flash rust if not rinsed and dried very well right away.

 

[Screwdriver]

Opinions on adding wallpaper paste to make a "paint-on" de-ruster?

Tried it, didn't work. I thought at the time that even if the thickening agent (I tried a fair few!) didn't react badly with the DCM, it would stick to the part ok but become exhausted. Unless the active ingredient can migrate, once the touching part of the coating is spent, the action stops.

I have a bucket of the stuff somewhere but decided not to keep it in the fridge (!) so it's probably a perfectly dry empty bucket by now. Then someone suggested you can still get the full fat real Nitromors and I gave up playing with the nasty stuff trying to copy it.