I recently purchased CRC Evapo-Rust as a soultion to my rusty metal problems. Needless to say this stuff works! Ive also been battling a mil-scale removal conundrum… flap discs/time/impatience/mess… i tried the Evapo-Rust on a clean piece of 14g HR steel and washed away my mil-scale with water. So happy!
Now to build dunk tanks/wash stations 
Hope this helps you guys!!
Shoutout to CRC… i would take a sponsorship deal 
I know this is an old post. How long did you soak for mill scale?
If your looking to remove mill scale from sheet products, buy P&O (pickled and oiled)
the cost is not much.
If you are looking to remove mill scale from tube look into Vinegar or Citric acid. Depending on how strong you make your mix it will take any where from maybe 8-24 hours. If you want to prevent flash rusting for several months follow up with a baking soda bath of 1 box (16oz I think) of backing soda to 5 gallons of water for 10 mins rinse and dry.
I’m sure Evapo-Rust is faster but its pricey! and I’m not sure you can just wash it down the drain
I have a 5 gallon bucket of it that I used in the past for very rusty stuff but didn’t consider it for mill scale.
of Vinegar?
You can buy 45% Vinegar which will make about 8-9 gals of store bought. If you want fast buy a gal of 45% and add to 4 gals water. I sometimes have to give a rub with Scotch-brite, but I mix 1 gal of 45% with 9 gals water and I use it 4-5 times. It gets weaker over time.
One thing I have found that makes it last longer is to wipe done your parts with wash thinner to get the oil off. Oil will contaminate the vinegar mix.
Don’t forget the baking soda mix it will keep your parts rust free for months.
Good luck!
Sorry Evapo Rust
FYI, you can buy a bulk bag of citric acid in solid form off amazon (easier to store long term)
www.amazon.com/dp/B00GNBHPAS
Mix as required.
Use pH paper to verify acidity:
amazon.com/Hydrion-paper-93-Dispenser-Color/dp/B005FYGXUC
You can also chelate the mix
I tried the citric acid and it set for maybe 20-30 days after mixing with water and there was 2-3" of white sludge/powder in the bottom of the bucket. I was able to mix it back up, but it all settled out again after 24 hours. seemed to work OK but made more work
Did you super saturate it? Temp change that made it fall out?
I dont know what that means. Im sure there was some temp change. Not sure what caused it
If you put too much into solution, it will precipitate out if it’s displaced by some other ions, or if the temp changes and condenses the water, giving “less room” to hold the chemical in suspension.
OK lets get this clear I’m no chemist! 
I mixed it just like the video you posted I used all his recommendations.
I’m not sure on this as I don’t remember the temp when I mixed it. I’m sure its warmer now then when I mixed it.
So are you saying water going from hot to cold or cold to hot? and how much temp swing?
I mean, neither am I. I just know things and drink whiskey.
Temp increasing usually increases reaction rate / keeps ions in suspension, temp drop usually condenses the atoms/molecules and precipitates. You likely super saturated the solution.
