Getting rid of dross or slag the easy way

[james.davis]

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Spray anti weld spatter on the bottom side of the plate you're going to cutting (the whole plate).Just one coat I spray side to side then up and down.
One can last about 4 8ftx 4ft sheets of metal
you can get it at a weld supply store.
After seeing the results you won't use muriatic acid again.
A can cost about $6.00.
You will be amazed.
Very little if any clean up
I added pictures to show the amount of dross right after cutting.
Jim

[acourtjester]

Great suggestion but I use the acid to removes mill scale and it really cleans the parts too

[Scratch]

I tried using acid for the first time a few months ago and wasn't in love with it. I had to wait too long, had to rinse the acid off, and it still left a "scale" that I felt I needed to remove with the wire wheel grinder before I finished it. I'll be trying the anti spatter spray method, as well as the oscillating tool method next time I cut.

[acourtjester]

I use a 50/50 mix and leave in for 24 hours this is 3/8" I cut for the gringer I built. I neutralize with washing soda and water blow dry.

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[Scratch]

I use a 50/50 mix and leave in for 24 hours this is 3/8" I cut for the gringer I built. I neutralize with washing soda and water blow dry.

Yeah that's the same "scale" I was talking about that I feel I need to grind off with a wire wheel. Do you leave that on and paint or patina right over it with no problems?

[acourtjester]

Ok we may not be talking about the same thing here are 2 images first shows dross and mill scale on the metal the second no dross or scale just bear steel. Now I have painted those parts after treating them as stated without problems. Here is a star I cut treated and clear coated years ago, been in my shop which is not heated or AC.

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[james.davis]

I wasn't talking about mill scale I was talking about slag and dross.Most of my work I use cold roll

[Scratch]

I was talking about the "scale" that I get after doing an acid bath. Not mill scale, or dross, but I get a white-ish color coating on the bare steel after I dip it in acid then wash it off. It's not a mill scale, and it comes off easily, but it comes off very easily, like almost with my fingers... and because of that, I feel I need to run a quick wire grinder over it before I paint it because I'm afraid it won't stick.

[acourtjester]

That is why I flush/rinse/neutralize in a bath of washing soda and water and a bristle brush and flush with clean water blow dry.

[Scratch]

That is why I flush/rinse/neutralize in a bath of washing soda and water and a bristle brush and flush with clean water blow dry.

Aahh, that makes sense, I wasn't cleaning with a brush like you do. That would take care of it.

Still not fully converted to using acid for removing dross. Anxious to try the anti spatter spray and oscillating tool.

[acourtjester]

One thing I would suggest when using acid after use return to a storage container I use 5 Gal Gas storage containers for mine. If left in a soak pan the fumes can cause a problem. Quick rust to untreated metal and the acid will lose its strength over time as it will off gas.
And use Personnel protection gear when using the acid. As shown there are other ways find what works for you

[steelfx]

Sharing Some Tips:
post by acourtjester » Tue Jan 28, 2020 9:05 am

One thing I would suggest when using acid after use return to a storage container I use 5 Gal Gas storage containers for mine. If left in a soak pan the fumes can cause a problem. Quick rust to untreated metal and the acid will lose its strength over time as it will off gas.
And use Personnel protection gear when using the acid. As shown there are other ways find what works for you

by Bill: Muriatic Acid Diluted in Water, in an open tank will off-gas, albeit rather slowly.
CAUTION: Returning "used" Acid Bath to Closed Containers could easily cause an explosion unless you leave a small breather hole. The liquid, after cleaning one steel or galvanized part, will be contaminated and will contain Fe, FeO2, which will continue to attack and react with each other. "Redox" is the chemical name for the reaction. The resultant expansion of trapped gases will eventually go "boom", or at the very least will rupture the Poly Gas Can. No fire, just a huge mess! Here's a test: In a 1-qt. plastic mixing cup, add 2/3 cup of 'used muriatic acid', 1 small scrap of steel, then cover tightly with 'Saran Wrap' and seal tightly with tape or a rubber band. Place it so as not to damage any persons or property and check on it in a couple hrs. Check on it from a distance. Wear Goggles!
The saran wrap, right before it pops will begin to look like a crystal clear "see-through balloon".
HCl (Muriatic, a.k.a. Hydrochloric Acid is a Gas, Suspended in Water). A cover will minimize any off-gassing and lessen the chances of iron/steel items beginning to rust from the fumes. There are no discernible 'fumes' when an Acid/Water 1:3 or 1:4 ratio is used. 1:1 a.k.a. 50/50 is way too strong and just a waste of money. The stronger the mix ratio, the faster it will off-gas.

Mention has been made (a few hundred times), that one needs to remove steel from acid bath, then place in Baking Soda Bath to neutralize.
This is an urban legend and patently untrue. You can't neutralize an acid that is no longer present.
A thorough water-rinse on both sides of each piece is ALL that is needed, followed by drying with shop-air. If you are most comfortable with the two-tank process, save yourself some money and just add 1 Tablespoon of Dawn Dish Soap to every 30 Gals. of Water. Liquid Dish Soap in water will 'neutralize' faster, as it has a higher pH, and will raise the pH of 'acid on steel' a lot faster than Sodium Bicarbonate. Whatever you do, don't use Sodium Carbonate (Washing Soda), as it has a very high pH (too high!), and will burn your skin. Liq. Dish Soap is Best.
Here's the best tip for preventing acid-tank evaporation, fumes and off-gassing: Use Float Balls. The Smaller the Ball Diameter, the better, as the smaller balls leave less 'gap' between each other. (I use 1" balls in a tank that is approx. 54" in diameter at the water-level, tank half-full).
There are approx. 700 balls in the photo below, at a cost of less than $60.00. You can google 'plating balls', 'float balls for plating', or I can give you a link to the ones I purchased.

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post by Scratch » Sun Jan 26, 2020 8:38 pm

I tried using acid for the first time a few months ago and wasn't in love with it. I had to wait too long, had to rinse the acid off, and it still left a "scale" that I felt I needed to remove with the wire wheel grinder before I finished it. I'll be trying the anti spatter spray method, as well as the oscillating tool method next time I cut.

by bill: Scratch, after 20-30m, hot-rolled steel, submerged in acid/water 1:3 will have all of the mill-scale removed. What's left (that looks like surface contaminant is clean steel, referred to as "steel in the white". It's not actually white, but that's what it's called.
If doing a patina or dye finish, steel "in the white" can be shined up with an angle-grinder & 80 or 120-grit flap disc in just a few minutes.
I use a 4.5" Single-Speed Makita® Grinder and a flap-disc (not to be confused with a flap wheel)...the two are totally different, and a flap-wheel is for paint and Bondo® removal. It won't shine up your steel. Total Dross Removal, in the same acid to water ratio, 1:3 can take up to 24 hrs., but it will remove 99% of your dross without the use of abrasives. When I DO need to knock off any dross from the backside, I use the same Angle-Grinder with a 24 or 36-Grit AVOS® set, which is a backing pad and very aggressive, replaceable abrasive disc. They're on my site, if you can't source them locally. My prices might be better, too. I buy the backing pads and discs by the thousands, so I get a pretty good deal.

I encourage experimenting and the use any and all tools, attachments and shop 'tricks' that y'all choose, but I would caution anyone doing metal finishing and plasma-cutting to not use 'anti-splatter' spray to reduce dross.
You don't want any type of mineral/vegetable oil, petroleum distillates or hydrocarbons on your steel. It's damn hard to get off and will cause de-lamination problems with clear-coats, powder-coats, patinas and sometimes, dyes. You just don't need it.
I personally do not own a wire wheel of any type. They don't have any redeeming qualities when it comes to metal (steel) finishing, IMHO.
Question: For my own knowledge, how would you use an "Oscillating Tool" in metal prep? I know what they are, but I can't picture the actual application or cost vs. benefit.
(It's hard to teach an old dog new tricks, ya know)??

[weldguy]

Awesome post Bill Thanks for extra info

[steelfx]

You're welcome!

[twelve02customs]

Thanks for the heads up. As I am starting from a base point of zero or less even, this calms any anxiety over using acid to help me make a better product to finish. Just a question though....do you segregate your acids? As in do that work/prep in a different area in your shop/setup?

[Dishtech55]

I read where ,Vinegar worked great to remove doss... Going to try it next week..Got 25 gallons of straight Vinegar coming..we will see.