DIY Rust Remover

[mdbuntyn]

I stumbled across this video demonstrating a rust remover made from water, citric acid, washing soda, and a little dish soap

 

[Martin Roper]

That should save me some money on Evaporust.

 

[J_Graham]

I've been using citric acid for awhile now. My only issue is that it leaves an really dull finish on the iron. But that may be standard for rust removal that I'm not aware of.
Additionally, if you do any home canning like I do I always have plenty of citric acid on hand haha.

 

[gamiller3rd]

Very interesting comparison. Thanks

 

[Gofor]

I have used the citric acid without the soap and soda as a rust remover, and it works well. I de-grease with Simple Green beforehand if necessary. Cheap and multipurpose (I also use it to descale the coffee pot, and as a cleaner in the washing machine and dishwasher). Biodegradable, so no disposal problems. Maybe not as quick as Evaporust, but it gets the job done.

 

[pop-pop]

Very interesting comparison. Thanks

 

[Rushton]

#1 on using citric acid for de-rusting. Works well. I've use both citric acid and white vinegar, the vinegar is a bit more aggressive, the citric acid best for parts with more delicate/intricate features. I've not use soap and soda in the process -- simple water rinsing has always worked for me.

 

[Rick_B]

I"m curious what concentration folks are using - i.e. citric acid granules per gallon of water?

Rick

 

[J_Graham]

I think when I have actually measured I use around a 1/2 cup per 3/4 gallon or so? You won't get it too strong. I've seen recommendations up to 1lb/gal

 

[Gofor]

I use about the same as J Graham for rust removal. I usually do at least an overnight soak, hit it with a brass brush, and then back in if needed.

2 tbs in reservoir full of water to descale coffee pot.

 

[Rick_B]

I'm looking to do a 2 ft square OSS table. In the current container I have (kiddie pool) that works out to 20+ gallons of water. I have heard 1 cup of Citric acid per gallon - that starts to get a bit expensive. I need to come up with another smaller container

 

[J_Graham]

@Rick_B i might look into uaing naval jelly for that size. You can use it a little more conservatively since it's a gel. If you havent used it before, use it carefully, it work really fast.

 

[Gofor]

I'm looking to do a 2 ft square OSS table. In the current container I have (kiddie pool) that works out to 20+ gallons of water. I have heard 1 cup of Citric acid per gallon - that starts to get a bit expensive. I need to come up with another smaller container

Will it take 20 gals to submerge the table? Less citric acid per gallon will mean slower, but it will work. Is electrolysis an option?

 

[Oka]

I have used Acetic acid (Vinegar) you can buy 30% strength at most hardware and big box, then dilute to 15-20%

Citric acid 15-20% or ........ Phosphoric acid I dilute to 15-20% they all work about the same.

Being Hawaii, rust is always an issue. The only real difference I see is phosphoric acid after rinsing does not flash rust immediately. Other than that, pick yer poison

 

[Rick_B]

Will it take 20 gals to submerge the table? Less citric acid per gallon will mean slower, but it will work. Is electrolysis an option?

I have a lot of derusting to do over the next year and I wold prefer something a bit less complex than electrolysis. I have never been successful with electrolysis - I suspect I would need to invest in a better power supply. I have heard a number of folks talk about using diluted molasses as a medium for rust removal - anyone tried that?

Rick

 

[NCTurner]

Instead of Citric acid, I use Oxalic Acid. It’s very effective and reasonably inexpensive. This product is also called wood bleach or wood brightener, it works great to clean oxidized fences and decks.

Amazon Oxalic Acid

 

[Jack A.]

For those who have used a simple acid rust remover (citric, acetic, etc.), what kind of surface does it leave behind? I used a commercial product on that Keen Kutter plane and it left behind a black material of some kind where the rust used to be.

 

[NCTurner]

For those who have used a simple acid rust remover (citric, acetic, etc.), what kind of surface does it leave behind? I used a commercial product on that Keen Kutter plane and it left behind a black material of some kind where the rust used to be.

Usually leaves a dulled steel, it does not convert the rust like what you are talking about.

 

[Gofor]

Red rust is ferric oxide. That is active rust eating at the metal. Black rust is ferrous oxide. This is when the rust becomes inert. (passivated). It is no longer active, and actually will protect the metal beneath it. So called "conversion coatings" are designed to make this happen, rendering the surface neutral and ready for painting. Conversion coatings for steel usually contain nitric acid. For aluminum, its phosphoric and chromic acid. In heavy deposits, ferrous oxide is also brittle, so when it cracks, it lets in new moisture and oxygen which start the rusting process anew. Acid based rust removers, as well as Evaporust, may leave deposits of ferrous oxide, especially in pits, that may require some mechanical agitation to remove.

A black residue on the surface is passivated light rust, and easily removed. The dull gray is the result of the rust and acid etching the surface so that it doesn't reflect light. It is the actual color of the metal.

Another method of rust removal is sodium hydroxide (quick lime, Draino crystals, etc). It is a strong alkali, and will remove organic paint coatings as well as the rust (doesn't work on epoxies and two-component polyurethanes). Down sides are it is extremely toxic, can easily permanently blind you if it gets into the eyes, and will burn your skin. It is what was used in slaughter houses to dissolve all unwanted parts of the animal. If you pour it out in the yard, nothing will grow there for a period of up to years. and you will have a black soupy mess as it dissolves anything organic in the soil. It eats aluminum, and will cause a violent reaction to it when in strong solutions. (Having witnessed this, its akin to pouring water into a pot of boiling oil)

A chemist could better explain the valence of the molecules and the reaction that leads to their forming.

 

[Gofor]

As a side note: It is not advisable to use acid removers on high strength steel, like grade 5 - 8 bolts, springs, ball joints, axle spindles, etc. When used on high strength and hardened steels, it can cause hydrogen embrittlement. This is when hydrogen infiltrates the surface of the metal, weakening it and causing cracks to form. The cracks propagate easily in the hardened steels, causing stress raisers that can lead to catastrophic failure (i.e snapping in half with no warning).