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Rust removers: Vinegar vs. Evaporust vs. Muriatic acid


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The trouble with acids, esp. strong ones like hydrochloric, is they eat everything, not just the rust. If you have deep pits and need to leave it in longer, you loose more of the part. Evaporust and other chelating agents don't eat good steel, just iron oxide.

 

I would be interested in a trial with oxalic acid and citric acid too. Both are chelating agents for rust; oxalic is better, according to a chemist who posted in a forum somewhere.

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Takes longer than the 5 minutes in muriatic acid but I like using electrolysis to remove rust: All you need is a non-conductive container like a plastic bucket, a battery charger, some sacrificial material and some washing soda. Doesn't eat up good metal and everything is pretty safe including easy disposal of the old solution if you don't care to reuse it.

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On 8/29/2018 at 6:29 PM, DonMicheletti said:

Boy, those cage nuts have had a hard life !  Mine kind of look the same way

 

Yeah my car has been through a lot. Cage nuts damaged by chisels tell of uncounted valve jobs by people with the wrong tools. It has a replacement upper crankshaft too, the engine has no serial number! Why would they replace that??? But the car is all there in solid condition, will be on the road again as fast as you can say Willie Nelson.

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Edited by Morgan Wright (see edit history)
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When you use muriatic acid in a glass bowl you can see what's happening and stop the action instantly. When muriatic acid is in an engine block you can't see what's happening and it could eat through a thin walled casting or radiator brass. It can also easily form pockets of acid that won't necessarily be flushed thoroughly when you think it might be finished. 

 

Stick with the agents that are known safe and effective. EvapoRust works very well, non-destructive, and not expensive. The chance of damage to your paint in case of a splash is gone. Time to retire those old school acids.

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Evaporust also cleans up chromed potmetal pieces nicely like chromed door handles with plastic knobs.  I throw all my stuff through it now.  I have a prokchop for my 47 hudson soaking right now as it will clean every nook and cranny front and back.  A light brush with a tooth brush and it will look like new with a rinse, sans any wear,  but you don[]t scratch anything up like you would with steel wool,  plus it cleans the rust on the pin for the knob so the knob spins better. 

Try it.  You will be amazed how nice stuff comes out.  You can even do it with nickel plated parts.  Takes all the green off and leaves them dull nickel.  A little polish with something like Mothers' mag and aluminum and they look wonderful without the scratching you get when trying to clean them with even 0000 steel wool. 

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You can buy evaporust off Amazon.  I think 4 gallons is around 80 shipped especially if you are a prime member. The cheapest they had it was 18 a gallon at autozone,  but they stopped carrying the gallon jugs.  I always bought atleast 2 when I went in. 

 

Porkchops are the Hudson guys names for the chunk of chrome ornament that goes on the front edge of the hood trim.  Especially with the step downs 48 and newer,  They really do resemble a pork chop. 

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If you ran a business and had lots of rust to remove, one job in, 3 jobs out, 5 more jobs came in before lunch, you want to get the work done so you can go home, you either do 5 minute soak in muriatic acid, which costs $6 per gallon and can be diluted 10/1 which means it really costs 60 cents a gallon, and still takes only 5 minutes.......or you can soak for 2 hours in something that is $18 a gallon that might not even work as well.

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Safety measures! (To avoid lawsuits)

 

1. there must be an eyewash on the premises at all times, and a hose for washing down spills on clothes or skin

2. vent hood with fan to remove fumes in the winter, garage door open at all times in the summer, or people will get stinging sore eyes

3. neutralize project with baking soda to prevent flash rust

4. increase insurance policy and no customers allowed in the shop

5. Die young from inhaling fumes, tell wife ahead of time

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Don't forget your epa Licensing and bonds to cover you incase you have a spill as well as disposal handling and transporting fees.  You have to produce alot of work fast just to pay all those fees and you will I'm sure be subject to unannounced inspections.  Any employees will have to attend a Hazmat course on your dollar that will have 4 hours of substance abuse training and 15 minutes of actual hazmatt training plus you will need local zoning approval and EPA approval for where you are going to use the product,  plus plans in place incase you have a Spill.

I might be missing something but that should cover most of it.  I'll use evaporust. 

Been using evaporust for 4 or 5 years now. Wish I knew about it much sooner.  If you need anything more aggressive than evaporust,  use the blast cabinet.  Works great on cadmium plated parts as well as onld door latches because it cleans off the rust on the internals,  leaves a near fresh plated look to the cadmium and degreases all the old dirty grease that full of years of shop crap if they are NOS parts.  Leaves NOS exhaust hangers with a fresh raw steel look and doesn't harm the rubber either. 

Plus you can get it on your skin and only in CA is it known to cause cancer,  but then again,  the label on the bottle and the sales receipt cause cancer in CA.

Edited by auburnseeker (see edit history)
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Once the rust is removed the iron needs to be protected so it doesn't flash rust. Best way to prevent flash rust is blue it. There are 100 ways to blue steel but they all involve heating the steel under oil. Heat the steel to drive all the water out, cover it with oil (any oil) and the surface will coat with ferrous oxide which is black. For the valve cage nuts I just simmered them in olive oil for a few minutes until they turned blue/black. Now they will never rust.

 

Ferrous oxide = black

Ferric oxide = rust

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Right after the acid they were grey and ready to flash rust, so I put a coat of black oxide on, for rust protection......I sprayed them with Liquid Wrench Lubricating Oil (not penetrating) and then put them in a frying pan and cooked them in corn oil on the stove for 1/2 hour. Heat the oil real hot, so it starts to smoke a little. Around 450 F. When it cools wash the oil off with detergent.

 

This black has nothing to do with carbon or charred oil, it's ferrous oxide which is black.

P1040304.JPG

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You could also take the part after painting it in dilute nitric or hydrochloric acid and allowing it to rust evenly, then drop it into boiling water. That will turn the rust to magnetite. This is called rust bluing. Repeat until the desired depth of colour is achieved or it won't darken further. Oil and stand overnight. This gives a deep blue/black finish.

 

You can do this without any acid too. Use a hydrogen peroxide and salt solution, sometimes with vinegar, to induce the rust. EPA don't need to be involved then!

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Actually according to the Evaporust can,  to prevent rusting, just dip it back in take it out and let it dry with the evaporust on it.  It forms a coating on it then.   I usually need a real layer of rust protection so it gets painted. If I'm going to sell it,  I spray it with WD40. 

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ply33 above was talking about electrolysis to remove rust. The best thing about electrolysis is that it removes rust real well and automatically leaves a layer of black oxide (ferrous) on the iron. In other words, electrolysis removes ferric oxide easily but cannot remove ferrous oxide, which is great because ferrous oxide is the best rust preventative of all. Gunsmiths always black oxide their guns so they don't rust. The cast iron frying pan on the stove is subject to rust if you clean it too much and leave it in the sink full of water, but if you cook something with oil (not butter because it has water) the pan turns black and never rusts, not only is the black oxide great at preventing rust, it's about as non-stick as you can get for eggs and pancakes taste great, much better than teflon, which is a worse non-stick surface and you wind up eating all the teflon when it chips off (that's not pepper in your eggs). Nothing sticks to a well seasoned cast iron frying pan thanks to black oxide.

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A couple of other rust removal media are 1)  9 parts of water to 1 part molasses. The kind you get from your local feed store.  This takes a while but if you're doing it for yourself, what else do you have.  Be careful though, it will destroy potmetal.  You need to rinse the part thoroughly after removing it and treat it with a metal prep compound of some kind.  Watch demonstrations on YouTube.  2) oxalic acid.  No real formula but you only need a mild solution.  At your local home improvement center, it's called Wood Bleach.  On eBay, you can buy a five pound bag of crystals for about twice what 12 ounces cost when sold as wood bleach.  The best thing about each is that they're both environmentally friendly. They both take time but they're both effective and CHEAP.  Two gallons of molasses costs about $4.  Five pounds of oxalic acid costs about $15.  Those amounts will last you a long time.  And both can be used in enclosed spaces.  If you leave the molasses outside, make sure you cover it.  Your local wildlife population will love its sweet taste.

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1 hour ago, RivNut said:

Two gallons of molasses costs about $4.  Five pounds of oxalic acid costs about $15. 

 

Oh boy, are you guys and girls rolling in clover! 500 grams (just over one pound) of oxalic acid crystals cost me ca 16 NZD and 5 L (about 1.3 US Gal) of molasses cost me 20 NZD. Chemicals for electrolysis were a lot cheaper, but they don't work inside something unless you can get an electrode in there.

 

2 hours ago, Morgan Wright said:

Gunsmiths always black oxide their guns so they don't rust.

 

Yes, rust bluing was developed for that purpose. Bluing is partial protection against rust. The oil is the secret agent for protection, reducing wetting and galvanic action. Bluing converts Ferric (Fe3+) oxide (Fe2O3) to Magnetite (Fe3O4, ferrous Fe2+ oxide).

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11 hours ago, Spinneyhill said:

painting it in dilute nitric or hydrochloric acid and allowing it to rust evenly, then drop it into boiling water. That will turn the rust to magnetite. This is called rust bluing. Repeat until the desired depth of colour is achieved or it won't darken further.

 

I don't believe this. Dropping a rusty part in boiling water blues it? No way. Painting with nitric and hydrocloric acid makes it rust? Nah. They remove rust.

 

I think the acid you painted on the part and dropped into boiling water is what removes the rust.

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14 minutes ago, Morgan Wright said:

I don't believe this.

Pity. It is true. You paint the acid solution on very sparingly. You can speed rusting up with heat, in a steam chamber for example.

 

Read Wikipedia about bluing. Read this web site about rust bluing firearms:

https://gunsmagazine.com/the-diy-rust-blue/

and this one:

https://www.americanhunter.org/articles/2012/8/31/rust-bluing-can-you-do-it-at-home/

and here is a bloke blogging about his experience:

https://www.americanhunter.org/articles/2012/8/31/rust-bluing-can-you-do-it-at-home/

and here is an article about it on Gun Test web site.

https://www.gun-tests.com/special_reports/accessories/Express-Rust-Bluing-Tips-Techniques-American-Gunsmith-14806-1.html

 

 

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Just for the sake of curiosity I put the pictured 1939 panel light switch in an Evaporust bath overnight. The switch was frozen solid . The second picture may not look all that dramatic but the switch is now working. It cleaned up nicely with absolutely no damage.

 

Another note on Evaporust: the manufacturer claims that a dip and then letting the part dry effectively blocks further rust, rinse it off with water when you want to refinish the part. Bought a 5 gallon bucket of the stuff at the start of my project and  enthusiastically recommend it. Bob H

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9 hours ago, Bob H said:

Just for the sake of curiosity I put the pictured 1939 panel light switch in an Evaporust bath overnight. The switch was frozen solid . The second picture may not look all that dramatic but the switch is now working. It cleaned up nicely with absolutely no damage.

 

Another note on Evaporust: the manufacturer claims that a dip and then letting the part dry effectively blocks further rust, rinse it off with water when you want to refinish the part. Bought a 5 gallon bucket of the stuff at the start of my project and  enthusiastically recommend it. Bob H

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I've done this with alot of NOS switches. Works really well on headlight switches with the rheostats that are all green.  The only thing I would recommend is not redipping the switches as the anti corrosion coating you put on may glaze over the contacts inside.  It will wear off eventually probably. With  switches I usually oiled them up with WD40 afterward just to help prevent the corrosion from coming back. 

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I have used phosphoric acid, with good results on old license plates that are too fragile for sandblasting or Hydrochloric or Sulfuric acids. It works well because it is a tri - protic acid (see Wikipedia). It is the stuff in coca Cola that makes Coke a rust remover. 

 

Phosphoric acid solutuion can be bought at farm supply stores, as it is used to clean out milk lines in dairy farms.

 

Does anybody know where to buy anhydrous (solid) phosphoric acid. it would be a lot cheaper than the farm supply store solution.

 

 It is  non toxic, but I would not try ingesting it. I have used Oxalic acid in my geochemistry lab tech days, and it is also a good rust remover.  But, it is toxic, so keep it out of your mouth, and wear rubber gloves. (It is what makes rhubarb leaves poisonous)

 

I want to try out the molasses solution.

 

What is the active ingredient in Evaporust? Sounds like it might be phosphoric acid.

 

Also, the electrolytic method with washing  soda and a battery charger works well.

 

 

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Not sure what Evaporust uses,  but it sure has alot of the characteristics of molasses.  It's almost like a refined molasses or extract of.  The same stickiness, though diluted, color and the fact it's non caustic. Though it doesn't smell like molasses. If someone wants to taste it.  Please get back to us ;)

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As has been said a few times, Evapo-rust is a chelating agent. This is from the MSDS.

image.png.982794e8d1cdc12177cb32aa1dfa8052.png

Molasses and oxalic acid and citric acid work the same way.

 

"Chelating agents are chemical compounds that react with metal ions to form a stable, water-soluble complex. They are also known as chelants, chelators, or sequestering agents. Chelating agents have a ring-like center which forms at least two bonds with the metal ion allowing it to be excreted. Chelating agents are usually organic compounds (a compound that contains carbon)."

 

When you have blood samples taken, EDTA is the chelating agent holding the haemoglobin (iron) in solution.

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10 hours ago, Morgan Wright said:

I assume molasses ferments into alcohol which ferments into vinegar. When people use molasses they say it takes a week to work, that's how long it takes for molasses to turn to vinegar.

 

I could be wrong.

Yep. Molasses contains a chelating agent, tho' a weak one. Vinegar has got nothing to do with it. My radiator surround was in it a month; no vinegar was made and the shell was derusted. The insects want to drink the molasses but drown in it.

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