How to Weld an Exhaust Pipe With a Stick Welder: Electrodes, Technique & Safety

The truck was up on jack stands in a driveway at eleven at night, and the only welder available was a 160-amp stick machine borrowed from a neighbour. The exhaust had cracked clean around a rusted joint about two feet forward of the muffler, and the owner’s question was the one this article exists to answer: can you fix an exhaust pipe with a stick welder, or are we about to make this worse?

That night we did fix it — with E6013 at low amps, stringer beads, a pipe rolled a quarter turn at a time, and a fire watch kept for the full thirty minutes after the arc went out. But the fix only worked because of everything that happened before anyone struck an arc: identifying the metal, cutting out more rust than felt reasonable, and accepting that the thin wall was going to dictate the amperage, not our egos.

Stick welding an exhaust pipe is a good demonstration of why SMAW is not the first choice for sheet metal. It can be done, it is fussier and slower than MIG, and it is the right answer in a specific set of circumstances. This guide covers how to do the job properly — electrode selection with real published amperage figures, technique that does not burn through, where to put the weld, how to keep it from cracking six months later — and where the boundaries are.

Short answer: Yes, you can weld exhaust with a stick welder. Use E6013 on clean mild steel at 45–105 amps depending on rod size, E6011 when the metal is too dirty to clean, stringer beads with no weave, the shortest arc you can hold, and short segmented runs with cooling between them. Know the metal first, keep the arc off the catalytic converter, and deal with the fuel system before you start.

People land on this topic for one of three reasons: they own a stick machine and nothing else, they are in a field or roadside situation with no shielding gas, or the metal is genuinely dirty, coated, or rusty and E6011 will handle it when nothing else will. If none of those apply and a MIG machine is sitting in the corner, use that instead — our guide to welding thin metal with an arc welder covers the heat-control discipline that applies either way.

Identify the Metal First

This decides everything, including whether you are welding at all. A magnet test is the fastest field check, and thirty seconds with the magnet saves an hour with the wrong rod.

If your manifold is cast iron and you have no choice, do not follow a mild steel procedure — the metallurgy is completely different, and the full method is covered in our guide on how to weld cast iron to steel.

Three things you should never weld onto

Catalytic converters. Welding heat damages the catalyst substrate and the matting that holds it, it voids the warranty, and attaching a canister to a pipe with a weld introduces vibration rattle and cyclic shock the unit was never designed for. On some designs only the pipe-to-flange joint may be welded, and even then the arc has to stay off the canister shell, the oxygen sensor bung, and the substrate itself.

Aluminized coating. Grind it back well past the weld zone. Residual aluminium in the puddle gives you an erratic arc and porosity every time.

Any part of the system you cannot fully vent. This is the one that actually gets people hurt, and it is covered properly in the safety section.

Why Stick Is Awkward on Exhaust

Exhaust tubing is thin. Common main pipe runs 16 gauge at 0.065 inch, with 18 gauge at 0.0478 inch everywhere that matters, and 20 gauge at 0.0359 inch in specialised applications. Now look at what SMAW brings to that wall.

The arc heat is concentrated and the pool is large relative to the wall — more heat to manage than MIG gives you, with less continuous control over it. Slag has to be chipped between beads, which on a thin wall means working close to a joint you can barely see. Spatter is heavier than GMAW.

Lincoln Electric’s sheet metal guidance covers 18 through 12 gauge for stick and warns that overhead welding of 18 gauge and thinner is not recommended — worth taking seriously, because overhead stick on thin exhaust tubing is exactly where burn-through rates climb. Their recommended approach for SMAW on sheet is low amperage, move fast, and whip or lap welds. In other words, a fight rather than a cruise.

Choosing the Electrode

Published amperage ranges differ between manufacturers, and the data sheet for the specific rod in your hand beats any general table. Here is what current products actually list.

E6013 — the default for clean exhaust tubing

Rutile coated, designed with sheet metal in mind, runs on AC or either DC polarity, lays a smooth bead, lifts its own slag, and restrikes easily. Lincoln’s Fleetweld 37 lists 50–80 amps AC and 45–75 amps DC at 5/64 inch, 75–115 AC and 70–105 DC at 3/32 inch, and 110–140 AC and 100–135 DC at 1/8 inch. ESAB’s Sureweld 6013 lists 60–90 amps at 3/32; Pinnacle’s E6013 lists 45–80 at 3/32. Note that DC electrode negative is a legitimate choice with this rod, not a mistake.

E6011 — for the metal that will not clean up

Cellulosic, deep penetrating, and unbothered by coating, rust, or galvanising. It is the AC-capable cellulosic, which matters if your machine only puts out AC. Lincoln’s Fleetweld 180 lists 40–90 amps AC and 40–80 DC at 3/32 inch, 65–120 AC and 60–110 DC at 1/8 inch, and 115–150 AC and 105–135 DC at 5/32. Use the middle of the range and hold 1/8 inch of arc or shorter.

E6012 sits in the same high-speed group as E6013 but is DC positive only, and its published ranges vary more by brand — check the sheet.

What not to use

E7018 and E7027. E7018 is an iron powder low-hydrogen electrode that needs a rod oven to keep its classification, and Lincoln’s Excalibur 7018 lists a 3/32 inch minimum of 70 amps DC positive. On 20 gauge tubing at 0.036 inch that is far too much heat — it will burn through. E7024 and E7027 are flat and horizontal only, which already disqualifies most of an exhaust system.

E6010 on AC. E6010 is DC positive only. This is one of the most common shop errors, and it fails immediately with no useful arc.

Electrode diameter and the rule that doesn’t apply

Most stocked E6013 begins at 3/32 inch; Lincoln starts at 5/64 inch; genuine 1/16 inch is scarce and expensive. The general rule is that the electrode should be smaller than the material thickness — one size down for material under about 3/16 inch. So 1/8 inch material takes a 3/32 inch rod, not a 1/8 inch rod. Loading a 1/8 inch electrode onto 1/8 inch wall is a common mistake that dumps heat into a joint with no margin.

As for the famous one amp per 0.001 inch rule: understand where it comes from before you quote it. It originates as a TIG and GMAW machine capacity heuristic — Hobart phrases it as a machine capacity guideline — and it is not in any electrode specification. Run it on 0.049 inch tubing and you get about 49 amps, while the published DC floor for a 3/32 inch E6013 is 70 amps. The rule lands below the manufacturer’s own minimum, which tells you it does not apply to stick electrode selection. Follow the data sheet.

Technique: Where the Job Is Won or Lost

Weaving is wrong here

This gets repeated constantly and it will burn through your pipe. Manufacturer guidance for E6012 and E6013 on sheet metal calls for non-weave beads or a slight weave, specifically recommending stringers or small weaves rather than wide ones to avoid slag inclusions. Lincoln puts it simply: it is not necessary to weave, and you should travel at a steady pace. The physics is plain — a weave means the arc dwells at the edges, where the pool has already been, and on thin wall that extra dwell is how you cut a hole.

Arc length has a sound

Miller’s SMAW guidelines are specific enough to be useful: a 1/16 inch arc with 1/16 and 3/32 inch electrodes, and a 1/8 inch arc with 1/8 and 5/32 inch rods. There is a diagnostic you can use without a ruler — a proper arc on these rods sounds like a crackle or a fry. If it sounds like a hiss, your arc is too long, and on exhaust tubing a long arc is more heat than the wall can carry.

Striking and tying in

Do not stab the electrode at the pipe like lighting a match. Strike it, slide it slightly away, then bring it back into the puddle — that initial slide establishes arc length without dumping the pool. For tie-ins, strike slightly ahead of the crater and move back into it, which gives you a clean tie rather than a cold one.

Rolling the pipe

Tack at roughly the 12, 6, 3 and 9 o’clock positions to get alignment and let distortion settle. Then weld in short segments: start at the bottom, work upward, and each time you finish a segment, skip roughly 180 degrees around the pipe and weld the opposite side, letting each go dull before you come back. This is deliberate heat balancing — it keeps distortion at one end of the pipe instead of walking it around. Lincoln also recommends lap or slip joints wherever possible on sheet metal, because they double the effective thickness at the joint.

Controlling burn-through

Drag angle of 10 to 30 degrees, stay ahead of the puddle rather than letting it catch up, and never stop moving to admire your work. The moment you hold the puddle in one place on thin wall, you are cutting a hole. If you want the wider discipline behind this, our thin-metal article linked above goes deeper — and if porosity shows up later, our guide to porosity in welding covers the causes you should rule out first.

Purging: What Stainless Demands and What Mild Steel Doesn’t

Back-purge with argon on stainless and this step becomes non-negotiable. The root face oxidises, and that oxide causes lack of fusion, root cracking and suck-back. Stainless tube and pipe manufacturers make argon back-purge standard practice, with flow continued until the root cools below roughly 300 °F. If you are welding stainless exhaust, do not skip it.

On mild steel it is optional, and for a different reason. Mild steel tolerates a slightly oxidised root — it scales and it will eventually rust from the inside, but it does not fail the way stainless does. The real concern on mild steel is slag and oxide falling inside the joint and getting trapped. So on mild steel, weld downhill and keep slag out of the bore instead of reaching for a purge bottle.

Protecting Everything Around the Joint

An exhaust system is a crowded place, and a lot of what surrounds it will not survive the heat. Heat blankets on anything adjacent — pay particular attention to wiring harnesses, fuel and brake lines, ABS module wiring, and oxygen sensors.

Miller’s guidance for SMAW on vehicles is blunt: disconnect both battery cables before welding on a vehicle, and place the work clamp as close to the weld as possible. Welding current travels the path of least resistance, and a clamp fifteen feet away will send some of that current through vehicle electronics and destroy them. Then check whether a fuel system is present and unvented before you start — that is the next section’s problem, and it is a bigger one.

Safety: The Part That Comes Before the Arc

Vehicle fuel systems

The big one. Do not weld with the engine running. Do not weld with a fuel system present that has not been drained and allowed to evaporate, or vented and tested. OSHA’s position is that hot work must not be performed in a flammable atmosphere, and hollow spaces must be vented or purged before welding. Under a vehicle you are also in a confined space with restricted access and poor ventilation, which brings carbon monoxide into the picture: OSHA’s general ventilation figure for confined space welding is 2,000 cubic feet per minute per welder, and no ventilation at all means a supplied-air respirator.

Fire watch, hollow spaces, fume, PPE

Maintain a fire watch with a trained person holding an extinguisher for at least 30 minutes after welding finishes, and relocate combustibles at least 35 feet away or shield them — OSHA 1910.252 requirements that apply whether or not you are welding exhaust. Vent the pipe itself before striking an arc: airflow through the far end prevents a pressure event and stops combustible vapour accumulating, and oxygen is never the ventilation medium — it creates an ignition source and accelerates combustion.

Mild steel fume carries iron oxide and manganese; stripped aluminized coating or stainless adds hexavalent chromium, whose OSHA permissible exposure limit is 5 µg/m³ over eight hours. Weld outdoors where practical, otherwise use local exhaust ventilation — see our deeper look at whether welding fumes are toxic. PPE: correct helmet shade, leather gloves, flame-resistant clothing with no polyester, and a leather apron, because you are underneath a vehicle with hot slag falling out of the joint. Cylinders upright, chained, valves closed when not in use. Our welding safety tips guide covers the shop-wide fundamentals.

Where to Put the Weld

The most common mistake on this job is not technique — it is location. In order of preference:

1. Cut out a section and fit new pipe. For a rusted-through pipe this is the only approach that lasts. A slip joint or welded socket in the gap gives you a fresh joint with sound metal on both sides.
2. Butt weld two existing pipe ends. Fine on sound metal — the normal repair for a crushed section.
3. Weld over an existing clamp joint. Easy, but the weld sits exactly where the leak already was, and clamp joints work loose, so it cracks eventually.

Do not weld over a V-band clamp. Do not weld onto a catalytic converter: the washcoat works inside a window of roughly 800 to 1,200 °F and welding near it destroys the catalyst, and removing a converter in a way that defeats it is a separate legal offence with fines attached. Mufflers and resonators are different — cracks in the shell and at the inlet and outlet are routine repair work. Stitch a strap or plate over the crack before welding so the patch does not carry the whole joint. And sometimes the honest answer is that a universal muffler costs less than the time and rework a repeated leak will consume.

Expansion Is the Real Enemy

A two-inch steel pipe expands about 0.016 inch per foot for every 200 °F of temperature rise. On a continuous exhaust system every joint is moving all the time, and that movement ends up concentrated at the rigid weld you just made. This is why exhaust pipes crack at the weld rather than in the middle of the pipe.

The practical consequences are worth memorising. Weld in short sections — 1 to 2 inch runs with cooling between them. Check alignment constantly and make the two ends concentric before you tack, using a straightedge across the joint. Tack, step back, look, then weld, because most cracking is alignment that was never verified. Never quench a hot exhaust weld: water on a hot joint produces a hard heat-affected zone and, on thin wall, immediate cracking. And remember that slip joints exist as thermal expansion joints by design — if your repair welds the entire system rigid, you have removed the movement the system depends on.

The same thermal cycling decides your filler choice. An ArcelorMittal and Valeur study cycled exhaust components between 250 and 950 °C and found that austenitic 308L filler on ferritic base metal cracked at the heat-affected zone or melted interface, because austenitic thermal expansion runs roughly 1.5 times the ferritic — while ferritic filler matched the base metal’s fatigue life. The practical conclusion for mild steel exhaust: match the filler to the base metal rather than reaching for stainless because it “sounds better.” The weld seam is a documented fatigue initiation site, and a mismatched coefficient makes it the weakest point on the system.

A Practical Procedure, Start to Finish

1. Identify the metal and the actual failure. Magnet test, visual, and an honest look at whether the part deserves welding at all.
2. Deal with the vehicle first. Battery cables off, fuel system drained and evaporated or vented and tested, exhaust pipe vented, combustibles cleared, fire watch assigned.
3. Cut out the failed section square. Angle grinder with a cut-off wheel is the usual choice on a vehicle — wheel rated for the material, eye protection plus a face shield, then deburr both ends with a file or flap disc. Oxy-acetylene is the right tool on heavy truck pipe, with a purge for fuel residue before igniting. Clamp a sacrificial square tube over the cut as a template: out-of-square ends produce a joint that fights you for the whole weld.
4. Fit the new pipe and check concentricity with a straightedge across the joint.
5. Tack at 12 and 6 o’clock, re-check alignment, then add the 3 and 9 o’clock tacks.
6. Set the rod and the machine. E6013 at the lower half of its published range, stringer beads, shortest arc you can hold.
7. Weld in 1 to 2 inch segments, alternating sides, working away from the ends, chipping slag between passes while it is still easy to remove.
8. Dress the beads flat enough that a slip joint will slide over them, and let the joint cool naturally.
9. Leak test before you reassemble anything.

Heat Tint: Reading the Colour Map

On stainless exhaust, heat tint is a colour map of the heat-affected zone. Straw or light gold is the lightest and usually acceptable. Blue and deeper colours mean more heat and more risk. Grey, black or heavy scaling means the HAZ is compromised — stainless that has gone grey or black beside a weld has locally lost its corrosion resistance. It only matters where corrosion matters, and underbody exhaust sees road salt constantly, so a sensitised HAZ on a stainless pipe in the salt belt will pit sooner than the rest of the pipe.

Leak Testing

• Soapy water and a rag. Detergent and water on the joint, watch for bubbling. Finds the leak you already know about.
• A smoke pencil. Blows visible smoke at the joint; good for small leaks over a wider area.
• A vacuum test. Small hand vacuum pump on the tailpipe. Many small leaks will not pull vacuum, and any sizeable leak shows immediately. Do this before reassembly.
• For a pinhole, an expanding pipe plug or a rubber-and-aluminium leak-stop patch is a legitimate field fix — not a structural repair, but it works.

Troubleshooting

The Honest Comparison: Stick vs MIG vs TIG

Most shops weld exhaust with MIG, and for good reason. GMAW with ER70S-6 at 0.023 inch and a C25 gas mix in short-circuit transfer is the standard: typical published parameters put 18 gauge at 16–17 volts and 180–230 ipm wire feed, and 16 gauge at 17–19 volts and 220–280 ipm. No slag to chip, less spatter, better heat control on thin material, faster. On a vehicle that needs to be back together, it is the right answer — and if you are curious about flux-cored alternatives for dirty field work, our dual shield welding explainer covers them.

TIG is the choice for stainless and for the cleanest cosmetic bead, with a back purge — but it is slow and unforgiving on a dirty, rusted mild steel joint, which is most of what driveway exhaust work looks like.

SMAW earns its place in three situations: no shielding gas available, metal too dirty for anything else where E6011 will bite in, and field work where a stick machine is what is on the truck. Everything in this article is written for those three cases.

Time, Cost, and Noise Reality

A single leak repair is one to two hours plus rod and consumables. Replacing a rusted-through section with new pipe is half a day. If the muffler or converter is the failure, the part often costs more than the labour did.

One expectation to reset: welding in a resonator or pipe section does not restore the sound a vehicle had new. If the goal is quiet, find the leak first — an exhaust leak is usually a louder problem than any resonator you can weld in. And on performance parts, note that most are aluminized or 409 stainless: both weld, both are thin, both distort, and 409 is ferritic, which is more crack-sensitive in the HAZ than 304. ER308L filler is safer than trying to match the ferritic chemistry when you are not set up for it.

Cutting Out the Old Pipe

Two workable methods, and the choice depends on what you can reach.

An angle grinder with a cut-off wheel is the usual choice on a vehicle. Use a wheel rated for the material, wear eye protection plus a face shield — you are cutting upward with sparks falling toward your own face — and cut square. Deburr both ends with a file or a flap disc, because a burr inside the bore traps slag and starts the leak you were trying to fix.

Oxy-acetylene cuts cleanly and is the right tool on heavy truck pipe, but check for fuel residue inside the pipe and purge before you ignite the torch. A fuel-air mixture inside an exhaust system is exactly the kind of surprise that ends a job permanently.

Whichever you use, cut square, then clamp a sacrificial square tube over the cut as a template. Out-of-square ends produce a joint that fights you for the whole weld — the gap is wide on one side and zero on the other, and you end up filling a hole instead of joining pipe. If the pipe is too far gone to hold a joint at all, you are no longer repairing it: cut back to sound metal further along, even if that means a longer replacement section than you planned.

Working Under the Vehicle

The awkward position is not a detail of this job — it is most of the job. You are on your back, looking up at a joint you can only partly see, with hot slag falling out of it.

Lincoln’s warning that overhead welding of 18 gauge and thinner is not recommended becomes concrete here. Everything is harder overhead: the puddle wants to fall out, arc length creeps longer because your arm gets tired, and burn-through goes up. The countermeasures are discipline rather than tricks — smaller rod at the bottom of its amperage range, shorter segments, more frequent pauses, and the pipe rolled so that as much of the joint as possible is vertical or flat before you commit to overhead.

Jack stands, not a floor jack. Chocks on the wheels that stay on the ground. A welding blanket or a piece of sheet steel between you and anything above the joint that can melt, and a leather apron because the slag finds the gap between your jacket and your belt. If the position is genuinely bad, the answer is often to remove the section and weld it on the bench — a slip joint makes that possible, and a joint welded comfortably on a bench beats a perfect procedure performed in a position you cannot hold.

Frequently Asked Questions

Can you use a stick welder to weld exhaust pipe?

Yes, with the right electrode and low amperage. E6013 is the usual choice for mild steel tubing, E6011 when the joint is too dirty to clean. The challenge is the thin wall, so expect a short arc, steady travel, stringer beads, and segmented runs with cooling between them.

What kind of rod for welding exhaust pipe?

Mild steel: E6013, or E6011 for rusted, coated or dirty metal. 409 stainless: a ferritic E409-type filler. 304 stainless: E308L. The common advice to use E308L on exhaust is wrong for mild steel — it is a stainless electrode, and an austenitic deposit on a thermally cycled mild steel pipe introduces the exact expansion mismatch that cracks exhaust welds.

What is the best welding method for exhaust pipe?

MIG for mild steel — faster, no slag, better heat control on thin material. TIG for stainless and the cleanest bead. Stick when you have no gas, the metal is too dirty for anything else, or a stick machine is all that is on the truck.

Should I preheat exhaust tubing?

No. Preheating thin tubing adds heat to a joint with no margin. The exception would be heavy structural steel near the repair, which is not typical on an exhaust system.

Is it safe to weld an exhaust on a car?

Only with the fuel system dealt with: battery cables disconnected, fuel drained and evaporated or vented and tested, engine off, the exhaust system itself vented, and a fire watch maintained. Under-vehicle work also means restricted ventilation, so carbon monoxide from the exhaust you are working on is a real hazard.

Why does my stick weld keep burning through?

Almost always too much amperage for the wall thickness, or a weave. Check the electrode data sheet rather than the one-amp-per-thousandth rule, drop to the lower end of the range, use stringer beads, and shorten the arc.

Should I remove the muffler before welding?

Good practice, especially on stainless or aluminized systems — it reduces heat mass near the joint and gives you better access. On a catalytic converter, keep the arc well clear of the canister entirely.

Can you weld aluminized exhaust with a stick welder?

Yes, but the aluminium-silicon coating has to be ground off in the weld zone first — well past the joint. Residual coating in the puddle gives you an erratic arc and porosity, and it is the single most common reason a first attempt on aluminized pipe looks contaminated. After welding, touch the bare zone back up with a high-temperature zinc/aluminium paint so the coating does not simply rust from the seam you just fixed.

Can you weld pipe with stick in general?

Yes — pipe of nearly any thickness is within SMAW’s range, and on thicker pipe you weld uphill on the root pass, then fill and cap. It is specifically thin exhaust tubing that is awkward, because the wall sits below where arc heat is comfortable.

Wrapping Up

Stick welding exhaust tubing works because E6013 was designed for sheet metal and because you can hold the heat back with a short arc, a steady hand, and a small electrode. Work outside the rod’s published amperage range and the thin wall will let you know quickly — usually with a glowing hole and a very quiet garage.

The three things that decide the job all happen before anyone strikes an arc. Know the metal, because mild steel and stainless need different rods entirely. Know whether the part should be welded at all, because converters and flex pipe cannot be. And know whether a MIG machine is available, because if it is, that is the faster and cleaner answer.

The rest is technique: stringer beads, no weave, a short arc that crackles instead of hisses, rolling the pipe to balance heat, slag off between passes, and a fire watch kept for the full thirty minutes. That driveway truck from the start of this article was still quiet a year later — not because the weld was beautiful, but because the metal was sound, the fit was square, and nothing about the job was left to chance.