[Colby]

Hey folks,
Been lurking a while, just got registered so I could start asking questions.

First one I have:
Using a Lincoln 140 Migpac, 25/75 gas. .030 Lincoln wire. Welding plain mild steel, well prepped and clean.
Just in the last couple days my welds have started to have a brown/rust type stain. Looks like brown soot around the edges on the base material.

I’m welding in my shop, no wind, 60 ish degrees.
New contact tip, 3-4 hrs max time on this welder and liner. Bottle and gas aren’t more than 6-7 months old.

Thanks for any suggestions,

Colby

[Darrin]

Not silicon deposits from the wire? Can it be removed with a wire brush? Flick up a pic if you can mate. I think running hot can cause silicon deposits? Someone here will know better than me, I’m just a hack!!

[Colby]

No, not silicon, it can be wiped away with a bare hand.
Maybe it’s nothing, but the recent appearance is what makes me question it.

[cj737]

Check your gas flow, likely insufficient coverage.

Also, remove your cap, clean your contact tip well, scrape any internal debris from the cap, then try it again.

Another thing some encounter is MIG gas can settle after time. Disconnect the regulator, cap your tank. Lay it on the floor, and roll it back and forth numerous times with your foot. Stand the bottle back, reinstall regulator, purge the lines, and try some practice welds.

[Oscar]

I don't buy the "mig welding as settles over time", but that's just me personally. Doing all that would just be more physical work to do, and if anything was fixed (again, this is just IMO), it was likely due to something else getting inadvertently fixed while doing all the disconnecting/connecting of the various parts/hoses. Argon and CO2 gases are very nearly the same density, so I don't believe any settling would occur. Liquids of varying density I can see, but not gases. Not trying to start a fight, just saying that I would love to read an actual scientific paper for this specific scenario.

One thing I have seen is different MIG wire will produce varying amounts of brown soot around the weld. Not a huge drastic difference, but enough to say "hmm, that's interesting".

[tweake]

i would think mig gas will settle over time.
even if they are similar density they are not the exact same.
keep the bottle still and consistently cold, any mixture will settle. if the bottle heats up in the sun during the day and cool down at night, thats enough to keep gases moving and mixed.
but if its kept cool and especially with big bottles (more mass to heat), the lack of temp changes means there is no energy input to make the gas move, so it will eventually settle.
it won't completely separate, it just means the mixture % will be a little bit different at the top than at the bottom.

[Poland308]

There’s been some previous posts about similar issues. One that’s probably from a year or so ago covered the issue of moisture in the gas causing contamination like your describing. As the pressure in the tank drops from use, it becomes easier for any moisture in you tank to travel with the gas. So a tank that was working fine when it was new may develop issues as it’s used.

[Colby]

Yep, I should have used the search feature first. Thanks for all the replies.

I’ll try them.


Colby

[Oscar]

i would think mig gas will settle over time.
even if they are similar density they are not the exact same.
keep the bottle still and consistently cold, any mixture will settle. if the bottle heats up in the sun during the day and cool down at night, thats enough to keep gases moving and mixed.
but if its kept cool and especially with big bottles (more mass to heat), the lack of temp changes means there is no energy input to make the gas move, so it will eventually settle.
it won't completely separate, it just means the mixture % will be a little bit different at the top than at the bottom.

Even if they were cold, the settling is far from noticeable.




from: https://physics.stackexchange.com/quest ... -container

I think that provides good insight.

[tungstendipper]

i would think mig gas will settle over time.
even if they are similar density they are not the exact same.
keep the bottle still and consistently cold, any mixture will settle. if the bottle heats up in the sun during the day and cool down at night, thats enough to keep gases moving and mixed.
but if its kept cool and especially with big bottles (more mass to heat), the lack of temp changes means there is no energy input to make the gas move, so it will eventually settle.
it won't completely separate, it just means the mixture % will be a little bit different at the top than at the bottom.

Even if they were cold, the settling is far from noticeable.




from: https://physics.stackexchange.com/quest ... -container

I think that provides good insight.

Huh?
Is that math? (as I raise my wooden cross)

[pgk]

Iv'e got a small bottle of C25 that I kinda misplaced placed, it's at least 24 years old and after I tested still works fine.Can't wait to see the look on my LWS guys face when he checks out the date it was last tested.

[LtBadd]

Huh?
Is that math? (as I raise my wooden cross)

Oscar is a math ninja

[Oscar]

Partly yes. That article is based on physics, the language of which is math.

Highlighted the original pic to illustrate the main points.

[tungstendipper]

I took Physics everyday for a year and loved it! Not the math. I still enjoy reading it; as long as you don't give test.

[starvncoyote]

Gases can and do unmix, but it would take a good year plus of sitting to do anything funky. If you can wipe the brown away, it may just be dirty wire or your volts are really high. I would go with the "hmmm, that's interesting" post and weld on.