Removing slag

[arp customz]

I cut alot of wind spinners and was wondering if any one knows a safer chemical then mernic acid to remove the slag?

[AnotherDano]

I cut alot of wind spinners and was wondering if any one knows a safer chemical then mernic acid to remove the slag?

Let's make sure we're using the right words.

Slag, Dross or Mill Scale.

Dross is removed with a flap disk, wire cup or sander. Slag is to a weldor as Dross is to a cutter. Same thing, in essence.

Mill Scale can be removed with muratic acid, vinegar or a bunch of other chemicals - or by grinding. Personally, I really do NOT like to have muratic acid around the shop. Pretty dangerous stuff - in the concentrated form especially.

Google Acid Magic or just 'mill scale removal'.

[steelfx]

I cut alot of wind spinners and was wondering if any one knows a safer chemical then mernic acid to remove the slag?

Let's make sure we're using the right words.

Slag, Dross or Mill Scale.

Dross is removed with a flap disk, wire cup or sander. Slag is to a weldor as Dross is to a cutter. Same thing, in essence.

Mill Scale can be removed with muratic acid, vinegar or a bunch of other chemicals - or by grinding. Personally, I really do NOT like to have muratic acid around the shop. Pretty dangerous stuff - in the concentrated form especially.

Google Acid Magic or just 'mill scale removal'.

A-Dano,

I respectfully disagree with the phrase, "Pretty dangerous stuff". When used correctly, it's one of the best time-saving
methods used in metal prep & finishing.
The type of Hydrochloric HCI Acid (commonly called: Muriatic Acid) that you buy at the hardware store is roughly
30-40% Strength. When mixed in the proper ratio with good 'ol H20, it's very safe.

Vinegar (Acetic Acid) will work if you've got a lot of time on your hands.

[AnotherDano]

I respectfully disagree with the phrase, "Pretty dangerous stuff". When used correctly, it's one of the best time-saving
methods used in metal prep & finishing.
The type of Hydrochloric HCI Acid (commonly called: Muriatic Acid) that you buy at the hardware store is roughly
30-40% Strength. When mixed in the proper ratio with good 'ol H20, it's very safe.

Vinegar (Acetic Acid) will work if you've got a lot of time on your hands.

No worries, Bill. I think 'When used correctly' is the key phrase. I had a bucket of the stuff splash over me many years ago and it ate through my shirt and jeans pretty quickly. Old experiences that make lasting memories.

Compared to strippers like B-17, muratic acid is like Kool-Aid. But that's a different application. I'll try some Muratic Acid on the dross. All I have to do is get around the aroma.

Thanks for the comment. I appreciate your experience and tips.

Dano

[stdave66]

Just a couple notes on my set up---I use the Muriatic straight, no water dilution, but you don't want to do this in the shop your working in! Vapors are nasty to breathe, and if you leave it open or in an unsealed container it will rust everything in the room.
I bought one of those plastic-rubbermaid deck chests (walmart) and keep the acid tub in it, outside of the shop. If temperature is around 70 degrees, mill scale be come off in about 25 minutes. If temp is around 30 degrees your looking at over 3 hours. I have a common heating pad under the acid tub to warm it on the days I need it (Yeah, winter time in Colorado!). Make sure you use a respirator with acid filters, they don't cost much and are much better than a wif of the nasty vapors. Is the set up a pain? No! Not compared to the agonizing grinding of the mill scale!

[steelfx]

Compared to strippers like B-17, muratic acid is like Kool-Aid. But that's a different application. I'll try some Muratic Acid on the dross. All I have to do is get around the aroma.

Thanks for the comment. I appreciate your experience and tips.

Dano

Try mixing the Muriatic Acid 1:1 with Water. The odor is almost undetectable. There's even an odor-free
Muriatic Acid on the market, but I've found it doesn't cut quite as well. Depending on how much dross is
occurring, 18-36 hrs. should be plenty of time to release most of it. The remaining dross can be blown off with
your shop-air. (Rinse parts with water first)

[boodog710]

I use muratic acid on a regular basis. As already stated, use outside and in a rubber or plastic tub. I also rinse the parts after removing them from the acid in a solution of baking soda and water. This neutralizes the acid. Just takes a second and it removes all acid on the parts.

[dreamer]

Hey Bill what about sand blasting the mill scale off or will that leave to rough of a surface for the patina?.........Harold

[steelfx]

Hey Bill what about sand blasting the mill scale off or will that leave to rough of a surface for the patina?.........Harold

Not a good idea for a couple reasons.
1) you don't want a blasted, matte surface for the patinas.
2) it's painfully slow & expensive. AL Oxide is the best media for mill-scale & It's not cheap.

Acid's cheap & it works.

[coupebuilder]

I had to chime in on this one, I own a custom auto fab shop and for years anything that was rusty would go to the glass bead cabinet---I mean literally hundreds of hours of cabinet use over the years. I recently found a used vibratory deburring machine (mr. deburr) on CL for 600 bucks including the media. I also bought 200# of coarse media online for around 250 bucks. We throw anything that will fit in the machine right off the CNC table and the coarse media will take off all but the worst dross and smooth out the edges...great for knocking off sharp corners on stuff that will be powdercoated. Using the fine media you get a surface that looks similiar to polished aluminum. I have seen these things for years and never realised how effective they are, now I am looking for another larger size. May be a little pricey for a small hobby business, but the savings in labor vs. blasting our small parts paid for it in less then a month.

[LNWelding]

Just starting out. Just finished cutting out my first piece to sell.

What is the best way to clean the metal? What types of grinders/chemicals should I use..... I'd gladly take any suggestions for all types of metal and looks! Thanks guys, appreciate all the help I get here!

Samantha

[tirediron]

Check out Steel - FX You will learn how to clean and finish your art.

http://www.steel-fx.com/

[aicomp]

Hi,
I read and asked questions here about Muriatic Acid. I have been using it now for a week or so. The results are incredible. The acid takes all of the mill scale and dross off. The cleanup is mostly just polishing the metal after the treatment. I use a flap disc and leave the swirls , as it gives a great finish. A 120 or 80 grit disc works best for me and I use a very light touch. I get my acid from Ace Hardware and put it in a large plastic tub with a lid. I use it 50/50 with water. Lasts a long time.
Mike

[Arc Innovations]

I was just wondering how all of you out there go about removing the slag off of the back of your projects?
So far, the quickest way I have found is to use a angle grinder with a abrasive disc. But with this, its hard to keep a clean look if you are trying to prep the piece for paint. I use a 80 grit flap disc for the front generally. And at $5.50 a disc, it gets expensive to use. Not only that, my arms feel like they are going to fall off when I am done!!!
Any suggestions?

Thanks, Gary
Arc Innovations

[jimcolt]

Depending on the plasma cutter you are using......always do a little tweaking of cut height cut, speed, and proper consumables set and power level.....you should be able to cut most materials virtually dross free, or at least have dross that removes easily. If and when I have dross....I first put the part on my bench and chip the dross with a scraper.....the chisels that you can buy in a hardware store that are used for masonry....are cheap, and have a good hard edge for chipping dross. Once the dross is chipped, then use a flap disc (60 or 80 grit, buy the good quality ones....they cost more, but last far longer than cheap ones) to finish up the edges. You will also find that by using the flap disc so that it is pushing the dross out away from the edge....as opposed to in towards the metal....that the discs will last much longer. You want the disc to cut the metal....not the sharp edge of the metal to wear the disc!

Dial in the plasma process....save time and minimize grinding!

Jim Colt Hypertherm

[boodog710]

Ditto on what Jim says. Except we use a 6" tool that is used to apply and smooth sheetrock mud. It will knock the slag right off. Then finish with a 60 or 80 grit grinder disk. Or you can use muratic acid.

Jack

[kel fab creations]

Hi,
I read and asked questions here about Muriatic Acid. I have been using it now for a week or so. The results are incredible. The acid takes all of the mill scale and dross off. The cleanup is mostly just polishing the metal after the treatment. I use a flap disc and leave the swirls , as it gives a great finish. A 120 or 80 grit disc works best for me and I use a very light touch. I get my acid from Ace Hardware and put it in a large plastic tub with a lid. I use it 50/50 with water. Lasts a long time.
Mike

i sometimes use straight muriatic acid to remove the coating on nuts/bolts for welding. rinse with water after, good to go. i have recieved parts from a waterjet company after they used acid (not sure what kind) to clean the rust and a day or two later they are covered with rust and i'm not in a high humidity area either. i like the idea of cleaning dross/rust by letting it sit in a bath but don't want to see rust soon after. have you encountered any of this? how long do you typically put stuff in for?

[Scratch]

I use what I call the "wheel of pain" which is just a wire wheel on a 4" grinder. Wear a leather apron when using it though, it got away from me once, caught my shirt, and ripped up my belly! Ouch!

But it removes the little bit of slag I get very easily. I also go over the front side to remove any smoke or anything on there. It's quick and easy.

Every once in a while, usually when cutting thick stuff, I'll get a big glob of dross. If it doesn't come off when I drop it on the floor or table, I'll take a standard chisel and small hammer and tap it off.

If you have a bunch of thicker parts, build a tumbler, or use an old cement mixer. I love those things, they clean off any and all slag, remove all the dust, lightly round the sharp edges and puts a nice almost blasted finish on them. But noisy as hell!

[stdave66]

I was using the flap wheels also but like mentioned before are expensive and don't last too long. I also didn't like that you had to watch carefully that all dross was actually coming off---easy to sand it down to a flat sliver still on the plate and not notice(at least me!).
Anyway, went to wire brush (Wheel of pain!)--the 2 3/4" knotted wire .020 on the 4" grinder---these work well but wear out fast (still use on more delicate stuff).
Now 90% of what I use are 4" diameter wheels of pain with .035 wire. These really rip the dross off! You better hold on! and you need to wear an apron or something for the shrapnel!
These are awesome but not so good for the calendar near the bench, got metal stuck 4 or 5 pages deep!
So...one particular piece I do with a lot of edges would take 30 minutes with flap wheel is now less than 2 minutes with the .035 wire wheel.

[BrianMick]

Word to the wise......use a leather apron when using the wheel'o'pain....It does not feel good when a wire off of those cups pierces the beans if you know what I mean.... I also learned to avoid grinding at that height....
Brian

[tm america]

I am thinking about trying the muratic acid to knock the dross off my parts.My question is gow does it work on aluminum?Does it eat away at it excessively?Also does the acid smooth out the cuts any?

[quadboy]

I just went through the hole thread. And I was wondering about aluminum too. Also what should I do with parts after they come out of acid and before welding on them? What works better all acid or 50/50 acid water? Anything but the grinder!!!!!!

[bmquist]

I ask the same as tm america and quadboy, regarding aluminium! doesn't anyone have an answare to our question

[abmetal]

Muriatic acid will dissolve aluminum. Take a penny, cut it in half and drop it in the acid. Then look at it the next day. All you have left is the copper cladding.

Allen

[quadboy]

So I guess it's the flap disc for aluminum.