Removing dross, mill scale from plasma cut parts

[cjdauthier]

Just wanted to pass along my experience with this...I have read several posts on this on here, and wanted to share....I started out the old fashioned way....abrasive disks and flapper wheels. They, of course, will do a great job of removing both dross and mill scale....just takes forever, especially when you have a couple hundred small pieces to do.....I then decided there had to be an easier way...so after doing some reading on tumblers, I built one out of an old propane tank with a 4 wheeler winch motor and bike sprockets for the drive gears...worked great...if you let it run for hours and didn't mind the noise....both of them were a pain to me...finally did a little more digging, and found the posts about muriatic acid...mixed 1:1 in a large platic drum...I cut the pieces, take them straight off the table and throw them in the acid solution...most pieces, even with heavy dross (I get in wayyyy too much of a hurry moving different thicknesses of sheets on and off, and alot of time just let her eat) are done in a few hours...mill scale, dross...all gone...just avoid the fumes, and save yourself some time...and work!!!!

I know this is well known to alot of you...but there may be a few people who, like me, were beating themselves to death with grinders and wire wheels....just wanted to share

[M & N Steel CNC]

OK, i am new to this, 1;1. muratic acid to what????

[Dawgonhawg]

The muriatic acid works well but how do you handle the rusting which starts very soon after using the acid?
Thanks, Dawg

[Kentuckyfarmer]

One part acid one part water
As to rust I wash the parts of with clear water after removing from acid tub and dry with the forced air kerosene heater this time of year, rust has not been a problem
hope this helps
Mike

[Dennis]

Can you post up a couple pics ---- Like a Before and After..

Thanks Dennis

[boodog710]

Mike, I have been using muraitic acid for several years now. After I remove the parts from the acid I put them in a solution of water and baking soda. This will kill any acid left on the parts. Only takes about a minute. Then I dry them and apply a thin coat of paint thinner. This will stop any rust. Works really great with a bunch of small parts. On large parts I use a sheet rock joint knife (6"). I simply knock the dross off with it. Then a light round with a grinder.

Jack

[Kentuckyfarmer]

Yea Jack I have used the baking soda after wash also it helps alot, I think the most important thing is a good rinse and quickly drying them dont hurt .
Mike

[DARRYL21270]

What are you guys storing your muriatic acid in. I just ordered a 40 gallon parts washer and was hoping I could fill that with my acid/water mixture or do you recommend using something else to soak pieces in?

[steelfx]

What are you guys storing your muriatic acid in. I just ordered a 40 gallon parts washer and was hoping I could fill that with my acid/water mixture or do you recommend using something else to soak pieces in?

I use a 300 gallon HDPE (Poly) Horse Trough. But I only have about 3 or 4" of solution in the bottom. That size
tank allows me to submerge a 4.5' X 3.5' piece w/ no problem. Keep it at least 50' or more from anything you don't want rusted, though & keep it covered when you're not using it. Muriatic (Hydrochloric) Acid is actually a gas that is suspended in water. Typically, the Muriatic Acid you buy at the hardware store is a 35-40% solution. Even diluted 1:1 with water
the fumes (gas molecules) escaping will rust anything in range.

There are "scentless" muriatic acids available, but they'll still rust things you don't want rusted & in my opinion, they're not as strong and effective as the regular. My favorite brand is TransChem?.

Bill

[rtsplace]

Hello All, I found a large flat tank sort of it's a cow foot bath come in 2 sizes. I bought the large one over 4' wide and around 8' long. current making a cover for it 2" thick foam board (pink stuff) it will take 2 sheets cut to 50"plus then seam together on 4 ' side, then I will bond rubber roofing to it all sides. Should make nice cover.

[ryno fab]

acid is the way to go. i just went to home d and got two of the biggest shallowest toats i could find. it came with a lid. a lid is a must. keeps the fumes in and the kids out. acid in one baking soda in the other. you have to neutralize the acid in the soda. i give mine a rinse in the sink and dry with an air hose. i also got a spay bottle. i take the parts that dont fit in the toat outside and hit em with that. its hard to get cold roll where im at and i blue almost all my artwork with a torch, so the acid really saves a bunch of time. also iff you pull it early and hit it with a sos pad you can get some cool results. the 50 bucks you spend is well worth it.

[DARRYL21270]

What's a toat ?

[ryno fab]

a plastic container. the ones i got are about 24x36 and only 8 inches deep. the even have little wheels on one end. anything poly will work. nothing metal. if you are note sure just put a little acid in there and wait a day or two to see. you really dont want that stuff on your concrete. it will eat the crap out of it. i wear glasses and gloves and hold my breath when placing an item in there. if you spill a little on you or the floor just hit it with the baking soda water. i dont know if it matters much but, i try not to put any hot metal in there. im not a chemest, but ive gotten it on me and it didnt kill me. i wouldnt put it in my coffee, and im not sayin you wont have an reaction to it. as for the soda i put a small box in about 5 ga of water and have another box on the shelf just in case.

[jimjimmac]

Read the reply I just posted in the 'Questions on Muric Acid' topic in the 'CNC Plasma Cutters General Forum' for an easy, cheap, and effective way to remove mill scale and weaken or remove the dross.

[roberttdonahue]

If you want to remove most of the dross quickly I found that if you take a smooth faced hammer and strike the edge of the piece, most if not all of the dross flys off with each hit. Just strike at the edge angled to the heavy dross side. It does not take too much force and it works great.

[metzindustries]

Thanks for the acid tip. I am going nuts trying to clean and prep 250 pieces of stove parts. The hammer does not work for the inside of small curves or lettering.

[Dawgonhawg]

What is the ratio mix used with the baking soda?

Thanks, Dawg

[mwade123]

I would also like to know the ratio of baking soda to water.

[steelfx]

What is the ratio mix used with the baking soda?

Thanks, Dawg

1# of Baking Soda per 5 gallons of clean water would be a good ratio. If you want to have an alkaline rinse tank & your tank is rather large, you could also substitute the baking soda (bicarbonate of soda) with lime (calcium carbonate), which is a lot cheaper.

Personally, I don't use a rinse tank with either product. It's not really necessary if you rinse your steel pieces well with water as soon as you remove them from the acid tank. I rest the piece on the edge of my tank & flush both sides of the piece with water, letting the rinse water go back in the acid bath. Then, I force-dry the piece/s with compressed air to
prevent flash-rust.

Bill

[mwade123]

awesome
Thanks Bill

[signsbyhansen]

I rest the piece on the edge of my tank & flush both sides of the piece with water, letting the rinse water go back in the acid bath. Then, I force-dry the piece/s with compressed air to
prevent flash-rust.

Do you find this dilutes the acid too much? How long does the acid stay good for if you leave it in the tank?

[steelfx]

I rest the piece on the edge of my tank & flush both sides of the piece with water, letting the rinse water go back in the acid bath. Then, I force-dry the piece/s with compressed air to
prevent flash-rust.

Do you find this dilutes the acid too much? How long does the acid stay good for if you leave it in the tank?

There's some dilution, but i just add more muriatic acid when I detect that it's taking too long to remove the mill-scale.
If you cover your tank to minimize evaporation & precipitation, it will last for months. You will have to refresh the tank with water and acid every so often. It's cheap.

Bill

[dgeorgester]

To remove most of the dross, I use a big old heavy file. I just swing it along the edges and most of the dross is removed. For the more difficult dross, a bit of tapping with the edge of the file is necessary. I also hit on the file with a hammer on the bigger pieces (1/2" thick and up). Be sure to wear your safety glasses. The dross really flies and you will really feel the pinch if you get it on bear skin. Finally, I just past the flapper wheel with the grinder.

If you see very small dross that is very difficult to remove, you just need to slow down the cutting speed a bit.

[Baileigh Inc]

All good info here, I think I'm going to try the acid thing. I spent all weekend hunched over my grinder........done with it.

[gusagus]

If you have a little time a cheaper solution is vinegar. Straight. I usually soak over night, pull my parts out in the morning, rinse, and a light hit with a flap disk. Dross and mill scall gone.