Author Topic: Mill scale removal  (Read 1864 times)

Essex_29

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Mill scale removal
« on: July 31, 2022, 09:07:38 AM »
I have no idea how well known this is, but I learned it pretty recently, how to easily remove mill scale from hot rolled sheet metal.
All you need is a (preferably plastic) container, big enough to hold the pieces of sheet metal you need to get cleaned, and enough Apple cider vinegar or acetic acid to cover the parts. I found 12% acetic acid for weed removal, and it works nicely and about the same as vinegar.
At about 30 degrees C (85 F) four hours is enough, but in cooler temperatures, say, like under 20 C (70 F) the process can take up to a couple days. If in a hurry on a cool day, you can put the container in a bigger container and fill that up with hot tap water.

For me, doing a lot of fabrication laterly, it's a real work saving way to get rid of mill scale. You just have to do it outsid, the smell is not all that pleasant.


After four hours, millscale has fallen to the bottom of the container

The metal looks bright and clean

After a rinse in water, and wash in a weak soda solution to neutralize the acidity the parts are sanded and look perfect, not much elbow grease needed.
Stronger acids would work faster, but using weak acids is safe and  easy.

TFoch

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Re: Mill scale removal
« Reply #1 on: July 31, 2022, 10:29:29 AM »
Great tip!  Welcome to the Rusty Bowtie Essex_29!
Spending time with my grandkids gets in the way of finishing my car but I don't regret it!

EDNY

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Re: Mill scale removal
« Reply #2 on: July 31, 2022, 11:14:01 AM »
I have been using apple cider vinegar in my ultrasonic cleaner and it works great.  A word of caution if you have for example "blued" gun parts....both the bluing and rust disappear ;D

Gun bluing is actually a type of rust made with hot salt baths.

Welcome to the forum!
33 Chevy 5 Window, 34 Chevy 3 Window, 37 Chevy 4dr sedan

Essex_29

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Re: Mill scale removal
« Reply #3 on: July 31, 2022, 05:17:49 PM »
Thank you TFoch and EDNY, both!

I'm amazed at how easy the mill scale comes off with weak acids like vinegar or acetic acid, as it's so hard to grind.

sixball

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Re: Mill scale removal
« Reply #4 on: August 01, 2022, 12:00:06 PM »
I did a demo at the Inliners International convention using food grade citric acid & water to remove rust. It won't harm paint and some stickers. It is good to know what other acids work for us. Thanks!
« Last Edit: August 01, 2022, 12:02:21 PM by sixball »
The probability of life originating from accident is comparable to the probability of the unabridged dictionary resulting from an explosion in a printing shop.  Edwin Conklin

Essex_29

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Re: Mill scale removal
« Reply #5 on: August 06, 2022, 10:33:25 AM »
Another few parts de-scaled. 12 hours in a cool average 65 degrees, and the mill scale just washes off. Engine and transmission mount parts here, just rinsed with water and hit with 80 grit on an orbital sander.
Okay, I'll leave this be now. It absolutely works, and is worth the while, especially with smaller parts and if you don't mind waiting a few hours or a day.

EDNY

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Re: Mill scale removal
« Reply #6 on: August 06, 2022, 10:59:56 AM »
Looks great...you are ready for some powder coating!
33 Chevy 5 Window, 34 Chevy 3 Window, 37 Chevy 4dr sedan

sixball

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Re: Mill scale removal
« Reply #7 on: August 07, 2022, 10:26:22 AM »
A great tip, Thanks. We all know the advantages of working with clean metal.
The probability of life originating from accident is comparable to the probability of the unabridged dictionary resulting from an explosion in a printing shop.  Edwin Conklin

 


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