[Jeff2016]

Hi,

I'm trying to follow all the good advice regarding clean base meatal for TIG welding.

Removing ALL of the mill scale with a Zirconium flap disc isn't working so well because it is loading up, nor has a course Scotch Brite sanding disc.

I'll try a siliconecarbide flap disc when I receive it. (Not quite sure i want to get into acid etching.)

In the meantime, how clean do most experience welders clean scrap for practice?

Thanks,

Jeff

[TraditionalToolworks]

In the meantime, how clean do most experience welders clean scrap for practice?

Most flap discs will fill up if the mill scale is thick, but they are about the best for smoothing out the deep scratches.

I would get a grinding wheel that you can swap out so you can save your flap discs when you really need them.

Most flap discs are not known for their longevity.

[DavidR8]

In the meantime, how clean do most experience welders clean scrap for practice?

I find that a coarser grit wheel cuts through faster and doesn't load up as much.
I bought a 10 pack of samples from Benchmark Abrasives. I'm quite happy with them so far.

[noddybrian]

A bit more expensive than regular discs ceramic abrasives work really well - they stay sharper longer & do not load up as easily - either fiber backed flat discs or flap discs will work on mill scale - stay with coarse grit size - if you can find & afford them try 3M Cubitron you will not be disappointed.

[v5cvbb]

I keep hearing about those 3M disc. Definitely need to try those. Wish they were more widely available.

[Coldman]

Grinding disc takes everything off without loading up and cheap. Also for flats and sections a coarse braided wire wheel on a 5" grinder strips off scale well without removing steel. It's a beast and you need to wear your leathers and ppe but I like it.

[smithdoor]

I just use a 4½" x 24 g hand grinder for all my cleaning

Dave

[Oscar]

Heavy millscale/rust, 4.5" or 5" air grinder with a 3M Cubitron II hard disc. Lots of normal/medium-high millscale/rust I use a 7" air grinder with a 36grit flap disc (which I will be changing to a 987c fibre disc). Otherwise, 4.5" air grinder with a 3M Cubitron II 987c fibre disc. If the the area is a tight access window, I have a 4" air grinder with again a 3M Cubitron II hard disk. Light millscale/rust, 2600 RPM air drill with a 3M purple silicon carbide 07479 XT clean strip wheel.

[Spartan]

You can also pickle the parts overnight in white vinegar for really thick mill scale, then just lightly dress them with a wire wheel or stripping disc when ready to weld.

As you can imagine, this is only practical for smallish/medium sized parts, and really only when you have A LOT of them.

It helps in some situations, though, and I do it several times a year when the situation calls for it.

[Jeff2016]

Hi Everyone,

Thanks for all the great advice!

I'll try the grinding wheel first.

I also like the idea of using the white vinegar (and not muriatic acid), even thought it take longer.

I appreciate the help.

Jeff

[JayWal]

Look up 3M Bristle Disks. You can get them in 4.5" for angle grinders or smaller ones for die grinders. They are excellent for paint removal as they dont take off any metal.

They also work really well for mill scale on tubing and flat bar. Not so much on heavier plate, they tend to overheat on that heavy scale so that's where I'd switch to hard rocks.

They are a bit pricey but work very well.

Sent from my SM-G970W using Tapatalk

[sbaker56]

I've found buying cheap flap discs in bulk is a good option for tubing and thinner sheet metal, with very light scale they'll take it off extremely fast without cutting in, and take a bit to load up. when you get to 1/8 plate they can be marginal depending on the scale, and they just load up almost immediately on thick steel. non woven stripper discs are fantastic for mill scale on anything up to 1/4 plate without digging into the metal at all. But they're expensive for their limited life span and shred when you hit a sharp corner or edge.

If you've got a big piece of 1/4+ with a heavy scale coating. The best way is really to just take a hard disc as a few people have mentions and do very light rapid passes with a small angle. You won't like the rough finish or the fact each pass leaves such a narrow strip but anything else will either be extremely expensive with how fast you'll go through discs or be grinding at a 12"x12" piece for hours trying to clean it completely.

[Jeff2016]

Hi Everyone,

Thanks for all the great ideas.

Here's the vinegar pickling vat in action.

Jeff

[MinnesotaDave]

For anything small, I prefer my blast cabinet.
Very even finish and welds really nice

[husq2100]

Hey all,

I just joined.

Where I live, Australia, all the mild steel I get is hot rolled and has lots of mill scale. I struggled with sanders etc, didnt like grinding for its gouging and all those clog up. Got switched on to acid.

I have a 20ltr bucket (6 1/4 gallons) with a 60/40 acid / water mix. Just hydrochloric acid. I put parts in it, go do something else, remove (strong magnet jambed in a pvc pipe) and rinse with water. Dry then sand with an orbital sander. very little effort and stuff comes up great.

[Oscar]

Hey all,

I just joined.

Where I live, Australia, all the mild steel I get is hot rolled and has lots of mill scale. I struggled with sanders etc, didnt like grinding for its gouging and all those clog up. Got switched on to acid.

I have a 20ltr bucket (6 1/4 gallons) with a 60/40 acid / water mix. Just hydrochloric acid. I put parts in it, go do something else, remove (strong magnet jambed in a pvc pipe) and rinse with water. Dry then sand with an orbital sander. very little effort and stuff comes up great.

Yup, that is another effective method. did you use "muriatic acid", which is commonly sold for swimming pools? It is mostly hydrochloric acid. Just be careful to not leave it in an enclosed area as the vapors are known to rust steel tools very fast.

[AndersK]

I like phosphoric acid. This is some brackets soaked in 21% mix after about two hours. 8mm hot rolled flat bar.
Welds nice and clean, no acetone just a quick rinse with water and let dry.

IMG_20200626_130145.jpg (87.37 KiB) Viewed 2550 times

IMG_20200629_195527~2.jpg (61.82 KiB) Viewed 2550 times

[TraditionalToolworks]

Yup, that is another effective method. did you use "muriatic acid", which is commonly sold for swimming pools? It is mostly hydrochloric acid. Just be careful to not leave it in an enclosed area as the vapors are known to rust steel tools very fast.

I've used muriatic acid in the past myself, but I don't like to use acid, just not good stuff to have around the shop, IMO, and not stuff you want to accidentally get on your hands or even clothes.

My problem with most chemical treatments is they take time, and when I want to weld I don't want to wait to clean it...

I did find the Cubitron II discs on Ebay and ordered 2 of them yesterday. Considering I can get several months from even a cheap Diablo wheel from Home Depot, these 2 should last me quite a while.

For anyone interested, this will save you from buying an entire box.

https://www.ebay.com/itm/3M-Cubitron-II ... 4330495398

[Spartan]

Yup, that is another effective method. did you use "muriatic acid", which is commonly sold for swimming pools? It is mostly hydrochloric acid. Just be careful to not leave it in an enclosed area as the vapors are known to rust steel tools very fast.

I've used muriatic acid in the past myself, but I don't like to use acid, just not good stuff to have around the shop, IMO, and not stuff you want to accidentally get on your hands or even clothes.

My problem with most chemical treatments is they take time, and when I want to weld I don't want to wait to clean it...

I did find the Cubitron II discs on Ebay and ordered 2 of them yesterday. Considering I can get several months from even a cheap Diablo wheel from Home Depot, these 2 should last me quite a while.

For anyone interested, this will save you from buying an entire box.

https://www.ebay.com/itm/3M-Cubitron-II ... 4330495398

Thanks for sharing that link. I just picked one up from that seller. Guess I'll see what all the fuss is about with these cubitron abrasives. 5 times the cost of my other grinding wheels, so hopefully it's 5 times as good

Nice to be able to get just one to find out, though.

[TraditionalToolworks]

Thanks for sharing that link. I just picked one up from that seller. Guess I'll see what all the fuss is about with these cubitron abrasives. 5 times the cost of my other grinding wheels, so hopefully it's 5 times as good

Nice to be able to get just one to find out, though.

I'm curious too and want to see what all the fuss is about myself. I don't doubt what people say, just haven't wanted to buy a box...I'm more than happy to pay a couple bucks more to get a couple singles. Not gonna break the bank.

I'd be curious to try one of the cut-off wheels, those can get kind of costly when they break. Not sure if the Cubitron is more durable or not. Anyone using the cut-off wheels?

[Oscar]

Thanks for sharing that link. I just picked one up from that seller. Guess I'll see what all the fuss is about with these cubitron abrasives. 5 times the cost of my other grinding wheels, so hopefully it's 5 times as good

Nice to be able to get just one ⅛to find out, though.

I'm curious too and want to see what all the fuss is about myself. I don't doubt what people say, just haven't wanted to buy a box...I'm more than happy to pay a couple bucks more to get a couple singles. Not gonna break the bank.

I'd be curious to try one of the cut-off wheels, those can get kind of costly when they break. Not sure if the Cubitron is more durable or not. Anyone using the cut-off wheels?

I have the 1⁄4" grinding discs in 4", 4-1⁄2", 5",7";
grinding/cut-off wheels ⅛" thickness in 4-1⁄2", 7";
cut-off wheels 0.045" thickness in 3", 4-1⁄2", 7".

The thin 045 cut-off wheels last a really long time for cutting, but unfortunately they are not impervious to sideways stress and will chip. Stronger than a cheapie for sure, but not impervious. They are still worth it IMO.

[LtBadd]

I like phosphoric acid. This is some brackets soaked in 21% mix after about two hours. 8mm hot rolled flat bar.
Welds nice and clean, no acetone just a quick rinse with water and let dry.

Hey AndersK, good to see ya in the forum, been awhile hope all is well!

[husq2100]

Hey all,

I just joined.

Where I live, Australia, all the mild steel I get is hot rolled and has lots of mill scale. I struggled with sanders etc, didnt like grinding for its gouging and all those clog up. Got switched on to acid.

I have a 20ltr bucket (6 1/4 gallons) with a 60/40 acid / water mix. Just hydrochloric acid. I put parts in it, go do something else, remove (strong magnet jambed in a pvc pipe) and rinse with water. Dry then sand with an orbital sander. very little effort and stuff comes up great.

Yup, that is another effective method. did you use "muriatic acid", which is commonly sold for swimming pools? It is mostly hydrochloric acid. Just be careful to not leave it in an enclosed area as the vapors are known to rust steel tools very fast.

I think thats what you guys call it, its just from our version of Home Depot and is for swimming pools. I think it is already diluted as in its not 100% acid by nature. But my 60/40 mix has been in use for 1 year now and still works fine. I keep it in a bucket with sealed lid outside. Always use glasses at a minimum. I tend not to worry too much about my hands as 25 years in construction has done more damage, and im only rubbing the parts under flowing water.

My uderstanding is that mill scale is a by prouduct of the process, the impurities floating to the surface. When you grind, sand, wire wheel etc, it slightly heats and liquidfies them and thats why all those get clogged.

As for time, acid really takes little time, maybe 5 mins on a new piece of hot rolled with complete mill scale. And it will even clean up good rust and mill scale. Ill try and get some pics