careful with evaporust

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hso

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Immerse the whole blade.

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I DID let it sit overnight. That dark area is the fill line of the container.

:oops:THEN I read the FAQs https://www.evapo-rust.com/evapo-rust-faqs/

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.
 
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I have used evaporust quite a bit, but never on anything where I care about the finish. I have rebuilt some wood machines where evaporust works great. The surface carbon is great at holding paint. It does a good job on rusty old hand tools too but you have to protect them with something after dipping them or they will start to rust again.

I wouldn't use it on a cherished knife or firearm like you found the hard way.
 
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First, it’s good to know Evaporust works. I have need of some in a saw blade knife project I’m working on. Second, that explanation of what happened is all over the place. I know if no mechanism that would bring carbon to the surface from the interior of a piece of steel except one and it requires some pretty serious temperatures. Also, in a general sense, steel is not porous.
 
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