So i have had several things turn a nice black, a hard to remove coating. First was a seating die that had some rust so i gave it a soak, came out a matte black nearly impossible to remove coating, then just yesterday i soaked a powder drop tube that i just bought and had a lot of rust. Same black coating. Now these items are obviously not ss or chrome plated as they rust, not sure what the manufacture does with the dies but the drop tube looks to be nicely polished mild steel. I have used Evaporust on lots of other steel pieces with no coating, so any ideas on why this is happening?
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Tips/Techniques Evaporust turning steel black
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Tips/Techniques
Doggggboy
Ultra Member
How long are you leaving it in?
trlvn
Ultra Member
From Evaporust:
The removal of the rust (iron oxide) reduces the proportion of iron to carbon, leaving a higher concentration of carbon on the outer surface. This heavier layer of carbon could cause a darkening of the metal due to the attributes of the carbon. The darkening does not have an adverse affect on the metal. It merely represents the movement of carbon from the interior of the metal to the exterior of the metal.
Since Evapo-Rust® is a highly effective rust remover, it stimulates the carbon migration process. Evapo-Rust®is not alone in creating the carbon migration effect. Other rust removal treatments will also result in carbon migration and a darkening of the metal. The primary difference between Evapo-Rust® and the acid based treatments is that Evapo-Rust® will not harm or weaken the metal. Unlike other treatments, Evapo-Rust® will not darken products made with low carbon steel.
With Evapo-Rust®, sometimes a wiping with a dry cloth or a more rigorous buffing can remove the dark coloring. A quick rinsing of the metal after Evapo-Rust® has been applied may also keep the carbon from settling into the pores of the metal.
There are several things that can be tried to minimize the effects of carbon migration. First, high carbon parts should not be soaked longer than necessary. Once the rust has been removed, the parts should be rinsed and dried. Second, a further dilution of the Evapo-Rust® formula may have a positive affect. The lower concentration of Evapo-Rust® will take longer to remove the rust, but may have less of an effect on causing the carbon migration.
www.evapo-rust.com
Craig
I got a black film on some parts after using Evapo-Rust®. What is it, and how do I remove it?
The black film is carbon from the steel. Steel is composed of a combination of carbon and iron. In certain instances, steel will darken in color after rust has been removed from the surface of the metal. This is a natural phenomenon that chemists refer to as “carbon migration”. The carbon from the steel moves, or “migrates”, to the outer layer of the metal and settles into the pores.The removal of the rust (iron oxide) reduces the proportion of iron to carbon, leaving a higher concentration of carbon on the outer surface. This heavier layer of carbon could cause a darkening of the metal due to the attributes of the carbon. The darkening does not have an adverse affect on the metal. It merely represents the movement of carbon from the interior of the metal to the exterior of the metal.
Since Evapo-Rust® is a highly effective rust remover, it stimulates the carbon migration process. Evapo-Rust®is not alone in creating the carbon migration effect. Other rust removal treatments will also result in carbon migration and a darkening of the metal. The primary difference between Evapo-Rust® and the acid based treatments is that Evapo-Rust® will not harm or weaken the metal. Unlike other treatments, Evapo-Rust® will not darken products made with low carbon steel.
With Evapo-Rust®, sometimes a wiping with a dry cloth or a more rigorous buffing can remove the dark coloring. A quick rinsing of the metal after Evapo-Rust® has been applied may also keep the carbon from settling into the pores of the metal.
There are several things that can be tried to minimize the effects of carbon migration. First, high carbon parts should not be soaked longer than necessary. Once the rust has been removed, the parts should be rinsed and dried. Second, a further dilution of the Evapo-Rust® formula may have a positive affect. The lower concentration of Evapo-Rust® will take longer to remove the rust, but may have less of an effect on causing the carbon migration.
The Best Rust Remover is Evapo-Rust® - No Scrubbing | CRC
CRC's Evapo-Rust® Heavy Duty Rust Remover is simple to use, reusable, and produces great results. No scrubbing. Just soak, rinse, and reuse!
www.evapo-rust.com
Craig
historicalarms
Ultra Member
Hmmm so basically a "no fire - no brilliant color " case hardening.
There is no acid in Evaporiust.
Tomc938
Ultra Member
I had the same thing with a piece of what I assumed was high quality(tool?) steel. It didn't turn the rust black, it turned the metal black. There was some deep rust, so I soaked it a few hours. After about an hour the steel was bright and shiny. The longer I left it the blacker it got. I'm going to cold blue it anyway, so no worried.
The evaporust did a nice job on the surface rust. I think my hopes were too high for the deeper rust pitting. Think I'll use my Dremel and small wire wheel and see how it goes.
The evaporust did a nice job on the surface rust. I think my hopes were too high for the deeper rust pitting. Think I'll use my Dremel and small wire wheel and see how it goes.
I do lots of stainless steel work, and after welding we pickle to remove heat tint, which is also carbon migration. For super aggresive tint, Antox pickling paste. For mild tint, citric acid, or powdered Barkeepers Friend stainless cleaner. Trick with citric acid or BF cleaner is to put a good pile of it on a damp paper towel, so it’s a thick paste. Rub the paste onto the work piece and keep rubbing until your arm is sore.
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Canadium
Ian
Once a long time ago I put a dividing head part into some old darkened evaporust. The part had rust on one section but was clean smooth and shiny elsewhere. The shiny part came out a beautiful black and I was wondering if this process could be used as a blackening agent. The black was not easy to remove. Seems to me there must be a little more to the chemical process than what is stated in @trlvn 's quote. My evaporust gets very dark after a lot of use and whatever makes it dark can get redeposited on new metal.
I'm not buying the migration of carbon story from evaporust. They need to stop smoking bad stuff at the customer support desk.
I do suppose it's possible that high carbon steel might leave a higher percentage of carbon that was already there than other steels do when the oxidized iron is removed. But it would take fairly high temperatures to move even a tiny number of atoms far enough to explain that.
I prefer the theory that different steels react differently to the rust removal chemicals.
Just sayin.
I do suppose it's possible that high carbon steel might leave a higher percentage of carbon that was already there than other steels do when the oxidized iron is removed. But it would take fairly high temperatures to move even a tiny number of atoms far enough to explain that.
I prefer the theory that different steels react differently to the rust removal chemicals.
Just sayin.
Why not leave it on? Especially if it acts as a corrosion barrier?
trlvn
Ultra Member
Do you know what kind of steel is in your "seating die"? (What _is_ a seating die?) Was there a thick coating of rust? If it is a high-carbon steel, that would tend to go along with the explanation from the Evaporust web site.
IOW, the more carbon that was present in the original steel, the more that will be left on the surface after chelation of the iron (rust).
Craig
(Not a metallurgist or chemist or anything related.)
IOW, the more carbon that was present in the original steel, the more that will be left on the surface after chelation of the iron (rust).
Craig
(Not a metallurgist or chemist or anything related.)
trlvn
Ultra Member
Overview of how chelation works:
www.zavenir.com
Craig
Chelating Technology | Metal Cleaning | Rust Remover - Zavenir Daubert
Zavenir Daubert RUST REVENGE is a ready-to-use water-based rust remover based on chelating technology. It is instrumental in metal cleaning and washes away surface rust form ferrous metals within 30 minutes to a few hours.
Craig
historicalarms
Ultra Member
A bullet seating tool for reloaders. Dies are made by a # of different manufacturers and metal harness/carbon content varies from one to another. I have altered quit a few dies to reload a meriad of obsolete cartridge calibers over the years and some will machine freely while others are hard as hell. There are some with a carbide shell inside....dont even try those.
Now this makes sense to me Craig. I'm not buying the carbon atom migration but a layer left over after the chemical reaction makes sense.
Both items had spot rust on them, not completely covered. On the powder drop tube it causes no issue, probably little to no issue on the seating die. Just wondering why those 2 tools would turn black when everything else was just fine. The post from trivn is way over my head, got kicked out of chemistry class a looooong time ago for some issue or another. A wad of firecrackers in a drawer may have been a bit to much fun for the teacher. Not that it was ever proven i did it......
KeeponDragon
no problems... just challenges
Is that the process shown every now n then when a welder lays down a nice bead of dimes, they rub some liquid on it, and the discolouring wipes off?
I've used household cleaning vinegar (slightly higher acidic level) to remove mill scale and rust from material before working it. It's amazing how well it works. But like mentioned by evaporust, rinse an dry afterwards. I got the idea from that Mike fella from Scotland, makes the Big Giant Swords on youtube...