LocostUSA.com

Removing mill scale is a time consuming, laborious process. Usually, I use an abrasive process like a wire wheel, flap disk, or a 3M plastic stripper disk on my 4-1/2" angle grinder. However, as a person who shares back issues with a number of other builders on LocostUSA, I decided it was time to work smart, and save what's left of my back if I can.

I'd seen videos on YouTube about ways to remove mill scale, and decided to give some of the chemical methods a go. I planned the experiment last week, but spent most of yesterday helping a neighbor clear a common drain, and boy do I need it to work this time. I'm really hurting today, and pain killers aren't touching the back pain. So, I'm taking a break and posting this.

I bought two chemicals to try: muriatic acid; and an industrial grade vinegar cleaner. That last one sounds weird, but white vinegar is one recommended method on YouTube. I couldn't find a gallon of white vinegar, but could find the ZEP industrial product at Home Depot and decided to try it instead.



Sunday night, I put some 2"x3"x0.120" mild steel pieces into a cheap plastic container,a and covered the parts with the ZEP vinegar.


I'd planned to work on them Monday morning, but due to the drain issue, put it off until today, Tuesday. So, I guess they've been in solution for around 36 hours. Here's what was achieved in that time.


I washed the off with a stream of water while brushing them with a small stainless steel brush. They really cleaned up well. All the rust, mill scale and paint came off with moderate effort. They need a little wire wheel time, but not much.


In the photo above, the last one brushed (foreground) is bright and shiny. The big one lying down has a slight orange cast to it. The first one done on the left has a discernible orange cast to it. I'm not sure why this is so. There wasn't enough time for oxidation to form. We're talking 15 minutes time between the 1st and 3rd piece.

I assumed it was some kind of chemical process caused by the vinegar. I thought I'd try neutralizing the vinegar (acid) with some baking soda (base) in solution and see if that stopped it.

After I post this and have some coffee, I'll go out and wire brush the neutralized pieces. If they spend overnight in the garage, and don't turn orange, I'll consider the case closed. I'll post again when I have those results.

There is one more thing. The two big pieces had to lie flat on their longest side to fit in the container and stay covered with vinegar. The sides lying down against the plastic container did not turn out well. So, I've placed them in solution again with the mill scale side up. I guess the not enough chemical got to the bottom side to react with it.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Very interesting experiment. I'll be watching this one with interest!!!

_________________
Mike - Read my story at http://twinlakesseven.blogspot.com/

Flash rust.

_________________
-Justin

Also follow my build on blogspot, tumblr, or instagram and twitter (GarageOdyssey)

Flash rust? Seriously? Wuz dat?

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Here's the overnight results.


The shiny piece I did on my usual way. I wire wheeled it with a electric drill, went over it quickly with emery cloth, and wiped it down with alcohol. In my world, it's ready to weld or be marked up using using machinists die and a scratch awl.

I consider the experiment a success. The piece on the left looks nasty, but it all came of in seconds very easily. I don't think I put more that 4 minutes into cleaning it up from wire wheel to alcohol wipe down. It sat overnight in the garage, and no new orange stuff appeared, so I think the baking soda soak stopped whatever was going on. The initial soak in vinegar takes overnight, but if you don't need something right away, it saves you a lot of effort over mechanical removal of the mill scale.

The muriatic acid is my next try (in a few days, maybe) because it only takes (they say) half an hour to work. I'm going to paint it on some raw material and then use water and baking soda to stop the process, and try knocking the scale off with a wire wheel as usual.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Lonnie, this is what you need!

https://www.youtube.com/watch?v=ACGSzBXKONo

_________________
Bill H
Winnipeg, MB, Canada

It's a common occurrence after 'wet' cleaning metal. As stolen from another website: According to the SSPC Protective Coatings Glossary, flash rust is "rusting that occurs on metal within minutes to a few hours after cleaning is complete. The speed with which flash rusting occurs may be indicative of salt contamination on the surface, high humidity or both."

It's totally normal and shouldn't be difficult to remove even without any additional steps. Rust removal using electrolysis will also have a type of flash rusting, even though it uses a basic electrolyte solution.

_________________
-Justin

Also follow my build on blogspot, tumblr, or instagram and twitter (GarageOdyssey)

Now, that's cool! Only $80K for the baby one, and $500K for the full deal, huh? Yeah, I might have to save up my allowance for a month or two.

Thanks, Bill.

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Ya learn sumthin' every day around here. Who'd thunk?

Thanks,

Justin

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

On little disappointment I discovered today is that the chemical effect dissipates in the vinegar solution. One YouTube video said you can keep it and reuse it. I didn't find that to be so.

The second batch I did with the two partially de-scaled faces and one new piece didn't clear up nearly as well. They cleared up about 80%, I'd say. It took a little more wire brushing to get them done. So, I'd say the vinegar is good for one batch and then you need to replace it.

I'd think the household white vinegar is likely cheaper than the industrial cleaner although I couldn't find gallon bottles at my local supermarket. I'll try harder to find it in future.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

I was kinda bummed when it didn't sublimate his hand. I was thinking this would be a great toy for my inner child

I use the Vapo-Rust sold at HF and most auto parts stores.
Probably a bit more expensive but it does re-use and has an additive to stop flash rust.
For large areas I use a paper towel to retain the chemical on the surface.

_________________
If I must be a one-man PC free zone, so be it!

My wife buys gallons of vinegar at the local grocery. It's her go to cleaning product.

This is a big topic on the CNC plasma forums. Guys try to save $4 per 4x8 sheet of steel and buy hot rolled. Then they spend hours cleaning up stuff to be paint ready.

I buy hot rolled pickled and oiled. cut, wipe, paint, done

What you're doing with the muriatic acid or vinegar is pickling. It makes the surface very reactive, so flash rust pops up in an instant. There's a cheap rust inhibitor that is water soluble. I can't remember the name right off hand. take parts straight out of the vinegar, rinse off the crud, and dip in rust inhibitor, or give a light oiling with a rag.

_________________
Too much week, not enough weekend.

OOPS I did it again
http://www.locostusa.com/forums/viewtopic.php?f=35&t=17496

Blood Sweat and Beers
http://www.locostusa.com/forums/viewtopic.php?f=35&t=15216

@TooBusy

Thanks for those tips.

Most steel suppliers in my area only stock hot rolled materials. I don't know why that is so. There is one supplier south of me in San Diego who has everything, but it's a 60-mile round trip too. So, if it's a small quantity I need, it's not worth the journey.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

For small parts, my go-to is phosphoric acid. I submerge the parts in it and leave it for a day or so. It is the active chemical in many commercial steel rust converters. It can be had many places. I have the remainder of a gallon that was sold as water softener cleaner/rejuvenator. It doesn't work as fast as muriatic acid but doesn't harm the steel that remains under the rust. It also leaves the surface treated with iron phosphate, a rust preventative. it stops the flash rust.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE