Re: [MW:35932] Black soot in MIG

Dear Mr. Anthony,

Black soot on Aluminized Mild Steel (ALMS) during MIG welding is a very common issue, and it 

typically indicates that the Aluminium coating is burning off and oxidizing not necessarily a weld 

defect, but rather a process/parameter & shielding issue. The soot is due to the vaporization of the 

Aluminium-Silicon coating and oxidation promotion due to CO₂. So, reduce the CO₂ content. Try 

92% Ar/8% CO₂ (best balance) or 95% Ar/5% CO₂ (almost no soot & very clean arc). 98% Ar/2% 

CO₂ is the cleanest but may affect the weld bead finish.

Further, for your 125A selection, 29.50V is too high and increases the heat input, and the vaporization 

and tend to distort. The ideal Voltage is between 20 to 22V. It will also help to reduce the spatter level. 

Pulsed MIG (if your power source supports Pulse) with a lower average heat input gives cleaner results 

on ALMS. 12 LPM is on the borderline for a coated sheet, and increase it to 16 LPM. Maintain a stick out 

of 12-15 mm and avoid excessive stick out to reduce the overheating and spatters.

As Aluminium coating cannot be removed prior to welding, we apply the Aluminium paint (at the weld & 

HAZ zones) after cleaning the soot, and it restores surface reflectivity, improves corrosion resistance (partially), 

and provides cosmetic improvement.

rgds,

C Sridhar.

Virus-free.www.avg.com

On Fri, 19 Dec 2025 at 11:39, pravin.n...@gmail.com <pravin.nimbalkar4@gmail.com> wrote:

Dear,

ER70S6 filler wire suitable but the problem is more about surface chemistry of aluminized steel and gas composition than filler wire choice.

My suggestion as below
1) Avoid pure Argon for MIG on steel—it can cause poor penetration and lack of fusion.
2) Change gas mix to 97% Ar / 3% O₂.This stabilizes the arc and reduces oxidation
3) Slightly increase gas flow i.e 14–16 L/min.
4) Use forehand (push) instead of pull to direct fumes away from the weld.

Regards,

Pravin Nimbalkar

On Friday, April 1, 2022 at 5:11:22 PM UTC+5:30 Anthony Dalisay wrote:

I thought of doing the same too, however, it will cost me down time to remove the surface aluminium of all the items (about 40k pieces). You are correct that it is natural tendency for aluminium to oxidize when diffused with the weld arc, although this seems to be illusive, would changing the gas flow rate(to higher), welding progression(from pull to push) and angle of torch and contact tip to work distance (CTWD) will help eliminate the black soot? I have not tried those I mentioned yet except adjusting the CTWD to much closer distance to base material but surely I will try and see if that would work. I you think I missed something out please feel free to mention it.

If this black soot still occurs, I might switch to High Purity Argon as my last resort and see if thats going to be a success. I let you guys know the result of this experiment shortly. I appreciate all your inputs.

Regards,

Anton

On Fri, 1 Apr 2022 at 7:10 PM 'james gerald' via Materials & Welding <material...@googlegroups.com> wrote:

Sorry i mistook it to be aluminium alloy 7065. IN Aluminiumized sheets welded using carbon steel filler you can prevent black spots by removing aluminium  from the steel sheet in the area of welding  and avoid diffusion of Al into weld metal as Al as a naturally tendency to oxidize as Al2O3

Thanks & Regards

J.Gerald Jayakumar

On Friday, 1 April, 2022, 04:25:10 pm IST, Anthony Dalisay <anthony...@gmail.com> wrote:

This is actually for motorcycle industry and the base material is not of any kind of pure aluminium series. It is an aluminized sheet welded by a robotic MIG using a normal carbon steel filler wire. With given parameters in the email thread.

Regards,

Anton

On Fri, 1 Apr 2022 at 6:24 PM 'james gerald' via Materials & Welding <material...@googlegroups.com> wrote:

seems to be like Aluminium alloy with slight additions of Zn, Mg & Cu mostly in Aerospace industries,

Thanks & Regards

J.Gerald Jayakumar

On Friday, 1 April, 2022, 09:26:43 am IST, Anthony Dalisay <anthony...@gmail.com> wrote:

Filler wire is ER70-6S @0.8 diameter size. 

On Fri, 1 Apr 2022 at 11:45 AM Kannayeram Gnanapandithan <kgpan...@gmail.com> wrote:

what is welding rod classification

THANKS & BEST REGARDS,

KG.PANDITHAN, BE, IWE,  CSWIP 3.1,

ISO 9712 Level 2 in VT,

ASNT-Level II in PT,MT,RT & UT,

LA ISO 9001-2015,

International Welding Engineer. 

CONSULTANT-WELDING & QUALITY

Mobile no: +919940739349

On Thu, Mar 31, 2022 at 3:36 PM 'james gerald' via Materials & Welding <material...@googlegroups.com> wrote:

Try AC current

Thanks & Regards

J.Gerald Jayakumar

On Thursday, 31 March, 2022, 01:03:59 pm IST, Anthony Dalisay <anthony...@gmail.com> wrote:

Dear experts,

We have been welding aluminized sheet using MIG welder with the following parameters:

Amps: 125

Volts: 29.5

TS: 50cm/min

Gas flow rate: 12L/min

Gas type : 18%CO2 and 82%Ar

However, I cant get rid of black soot (smoke) in the weld vicinity. What do you think, is the best way to do to achieve cleaner weld in aluminized sheet such as this? 

Refer to attached photo for reference.

Thanks in advance for your expert advice.

Regards,

Anthony

--

Anthony Dipasupil Dalisay

TWI AWeldI

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/CALBzUBLiVBU2wnkd3MGhgAMdC%2BMzEjF4SXM%2BsdgMXQgp5MVh9Q%40mail.gmail.com.

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/1137188882.137058.1648720763794%40mail.yahoo.com.

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/CAJzm4ePZEcu3VQAqckVb0QXUPyn68MgPEG3szWJQFaSr%3DVKPHA%40mail.gmail.com.

--

Anthony Dipasupil Dalisay

TWI AWeldI

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/CALBzUBLgwY9%3DoWBvvDCygdJi36BCdbwcN0kf_MU1Kc%3D91%2BQ4cA%40mail.gmail.com.

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/813151293.374227.1648808146903%40mail.yahoo.com.

--

Anthony Dipasupil Dalisay

TWI AWeldI

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/CALBzUBJ-XjUvApj6o_Fd1tS%2BNntpYzvQMETkVrcDRFOpkoKnhQ%40mail.gmail.com.

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-weld...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/1902270276.309839.1648811313312%40mail.yahoo.com.

--

Anthony Dipasupil Dalisay

TWI AWeldI

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-welding+unsubscribe@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/materials-welding/d523a089-c8d7-42c7-abf2-d16e77163089n%40googlegroups.com.

--
https://materials-welding.blogspot.com/
https://www.linkedin.com/groups/122787
---
You received this message because you are subscribed to the Google Groups "Materials & Welding" group.
To unsubscribe from this group and stop receiving emails from it, send an email to materials-welding+unsubscribe@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/materials-welding/CAHo%3DYigPxh3F%3DCCh_Kq3vdH6be6SJvtcajJUTAF1jUu9Yk1Gew%40mail.gmail.com.