homemade citric gel..what ratios

[steveo3002]

tried some wallpaper paste and citric power earlier , wasnt sure on the ratios?

i had like a egg size blob of wall paper paste and put say 4 teaspoons of powder in, will that work?

 

[badabec]

One way would be to make a saturated solution and use that to mix up the paste.
It will have to be kept wet or it won't work.

 

[Kram]

To how much water?

Id suggest follow the normal ratio of wall paper paste to water, or perhaps a bit thicker, that makes a good gel.
The problem with citric is that it does sod all if its not hot. Applying it as a gel implies a difficult or vertical area of a large part that cant easily be submerged or heated.

A cold gel will do nothing, very slowly! You may want to use a stronger acid.

How bad is the part? A light surface clean or prep before paint, or a deeply pitted, more rust than metal?

 

[Turbo]

I think the problem with gel is that there is only a small portion of the citric in contact with the metal. It soon becomes neutralised so no longer does any cleaning and the rest of the acid is held in the gel so cannot act on the metal.

 

[Screwdriver]

The acid will attack the cellulose and thin out the paste. I tried a similar thing using methyl cellulose to fake up some Nitromors (thread on here somewhere). The problem is you need the acid to be relatively mobile in solution. That is effectively what heat does by keeping the molecules agitated. A cold citric bath works a bit more slowly but it's not an order of magnitude different, just affects the time it takes to work. I guess boiling citric (it is a robust organic acid and it's ok to boil it) would make the solution work 3-4 times faster than say at room temperature.

 

[Kram]

A cold citric bath works a bit more slowly but it's not an order of magnitude different, just affects the time it takes to work. I guess boiling citric (it is a robust organic acid and it's ok to boil it) would make the solution work 3-4 times faster than say at room temperature.

Incorrect. A well known scale for chemical reactions is that is at 10c it takes 24 hours, each 10c of heat added will half the time. At 60c it will be done in 45 minutes and boiling under 3 minutes. This fits my experience of using citric.

If the part is cold, be prepared to leave it a day or possibly a week with occasional agitation/renewing the solution.

 

[mightymig]

Assume you want the gel because whatever you're cleaning (de-rusting?) is too large to dunk in a bucket? Here is the best one I used (non-gel) which is actually a home made evaporust chelating version which is more gentle on metal:

 

[steveo3002]

its on a car body , so yeah needs to be gel

 

[mightymig]

The only time I used a gel was with wallpaper paste and sodium hydroxide as a paint stripper and it worked very well

 

[mightymig]

Worst part about citric / evaporust is the dark colour you get with the layer of carbon - I want to try getting some graphite scrap to make electrolysis a more practical solution that doesn't need to be constantly baby sat

 

[Misterg]

Assume you want the gel because whatever you're cleaning (de-rusting?) is too large to dunk in a bucket? Here is the best one I used (non-gel) which is actually a home made evaporust chelating version which is more gentle on metal:

I was going to suggest that too.

Somebody on youtube has made this mix into a gel by heating it with cornflour. I was going to try the wallpaper paste route (just use the solution to mix the paste with).

 

[badabec]

Flapdisc?

 

[Misterg]

Assume you want the gel because whatever you're cleaning (de-rusting?) is too large to dunk in a bucket? Here is the best one I used (non-gel) which is actually a home made evaporust chelating version which is more gentle on metal:

Previous thread:

Thread 'Home made "Evaporust" formula'

Jul 27, 2024

I came across this video, a famous YouTube gunsmith has published a rust removal recipe that uses the same chemical mechanism as Evaporust. For those who don't know, EvapoRust uses chelation instead of acid and has the advantage of not damaging the base metal. It works great but is very expensive. This guys formula is slightly acidic but a fraction of the cost and lasts longer.

I've watched this YouTuber before, he comes across as honest, so worth trying his mix.

• rcx132
• Replies: 105
• forum: Paint, Metal Coatings and Media Blasting

• 
• 

It works very well, but you need to let things soak (there don't seem to be any ill effects from leaving things too long).

 

[mightymig]

There should be no huge ill effects on metal removing or aggressive eating of good material, but the longer you leave it I find the worst the darkening / soot like build up once the rust is gone. Theres a few EDM places near me and I might give them a cheeky call to get some scrap graphite and do an electrolysis test again but without steel anodes.

 

[dieselsamurai]

its on a car body , so yeah needs to be gel

I did the whole chassis of my chevy truck , just got to move it around with a brush every few hours I left it on for a day or 2 cant remember now worked really well though. In this weather you need to keep it covered so it doesnt dry out

 

[mightymig]

I did the whole chassis of my chevy truck , just got to move it around with a brush every few hours I left it on for a day or 2 cant remember now worked really well though. In this weather you need to keep it covered so it doesnt dry out

Yes when I did a gel paint remover I wrapped it in cling film

 

[steveo3002]

well i tried it , egg size blob of paste and 3-4 spoons full of powder , left on all day yesterday , then wiped off and new put on before bed , seems to have cleaned it up okay , paste wasnt a joy to use a bit to blobby

 

[Screwdriver]

Incorrect. A well known scale for chemical reactions is that is at 10c it takes 24 hours, each 10c of heat added will half the time. At 60c it will be done in 45 minutes and boiling under 3 minutes. This fits my experience of using citric.

If the part is cold, be prepared to leave it a day or possibly a week with occasional agitation/renewing the solution.

Then we must agree to disagree. I am not going to argue with you since I am not a chemist. Having said that, I have a ton of experience using citric acid after introducing this technique to the forum many years ago.

But I did check up on your objection. There are plenty of articles on researchgate.net which I have no intention of reposting here except to say the "sweet spot" appears to be circa 50ºC after which the speed up effect of heating compared to room temperature (circa 3-4 times as I guessed) tails off as temperature is increased further. Also heating both the part and the solution increases the possibility of damage due to etching the parent material.

On top of that you would be complicating an otherwise extraordinarily simple bucket of citric with a heating system and if you were going to do that, you'd probably be better off experimenting with electrolytic rust removal (which I also have documented here over the years). There is interestingly a similar trade off with speed (increased current) and parent material damage. Low current, slower electrolysis is a lot less damaging to the part where at higher rates, you run the risk of wiping off surface detail/finish in a more violent reaction.

I tend to boil up a citric dip anyway prior to using it firstly to ensure the citric dissolves completely and secondly to speed up the reaction initially. Much easier to scrub and check the part(s) as the solution gradually cools over time so that I can avoid going too far and damaging the part.

Next time I am derusting a few items, I'll be sure to test your assertion though tbh, I dread to think what the difference will be between a few hours cold soak and a 3 minute boil on the finished part. I'll do it with something cheap and disposable....

 

[Turbo]

Citric mix at 70 degrees c will dissolve cast steel brake calipers if you leave it in more than a few minutes.

 

[Ross365]

This question of doubling the rate of recaction for each increase in temperature causes endless arguments. It comes out of the Aarrhenius equation https://www.google.com/search?q=arr...HAzIuM7gH9ATCBwcyLTMuMS4xyAcz&sclient=gws-wiz, but in truth, it only stays true for some reactions (mainly simple ones) but often fails miserably to predict real behaviour.

I remember testing some EPDM rubber in an aggressive chemical; the material looked brilliant at 20,30,40'C (and seemed to obey the rule) but at 60'C it was rubbish. I was once involved in a tests on stainless at 650 and 820'C. The higher temperature oxidises less because the chromium can scoot down the grain boundaries at that temperature and form a more protective oxide layer.