TIG Welding Copper: Amperage, Preheat, and Filler Settings That Actually Work

Copper is one of the most electrically and thermally conductive metals you will ever try to weld, and that conductivity is exactly what makes it punishing on the torch. Most guides tell you to use more heat and preheat your part. Few tell you which copper alloy you actually have, whether TIG welding is even the right process, or what your settings should look like at each thickness. This guide covers all of it, including the specs most articles skip entirely.

Why Copper Is Hard to TIG Weld

The Thermal Conductivity Problem

Copper conducts heat roughly 60% faster than steel and about eight times faster than stainless. The moment you establish an arc on copper, the heat you are trying to concentrate in the puddle races away from the joint and into the surrounding base metal. The result is that you need far more amperage than the material thickness would suggest, and even with the right amperage, you can still lose the battle if the part is cold.

This is not just an inconvenience. It changes everything about how you set up the weld, from the amperage and preheat to the shielding gas and torch selection. Welders who approach copper the way they approach steel almost always encounter lack of fusion, wandering arcs, and frustrating porosity.

Oxidation and Porosity in ETP vs. Oxygen-Free Copper

Copper oxidizes aggressively at welding temperatures. The copper oxide that forms in the heat-affected zone weakens the joint and creates pathways for contamination. If your copper contains dissolved oxygen, as some common grades do, that oxygen becomes a direct source of porosity and embrittlement in the finished weld.

Understanding which copper alloy you have is not a detail. It determines whether TIG welding is even a viable approach, which filler metal you need, and how much trouble you should expect. Always identify your alloy before you strike an arc.

Identify Your Copper Alloy First

C11000 (ETP) — Why Oxygen Content Causes Trouble

C11000, also called Electrolytic Tough Pitch (ETP) copper, is the most common copper in the world. It is used in electrical bus bars, wire, sheet stock, and general industrial applications. It is also the most problematic copper alloy to TIG weld, and understanding why matters before you spend hours setting up a weld that is going to fail.

ETP copper contains between 0.02% and 0.05% dissolved oxygen. That oxygen level sounds insignificant, but at TIG welding temperatures, it reacts with the hydrogen present in the atmosphere and from contamination sources to form steam inside the weld pool. The result is porosity and grain boundary embrittlement, a condition sometimes called hydrogen embrittlement, that can crack the weld under mechanical stress. If you are welding bus bars or electrical conductors made of C11000, you face a real risk of producing welds that look acceptable on the surface but have compromised structural and electrical integrity internally.

The practical workaround for ETP copper is to avoid pure copper filler and use a highly deoxidized filler like ERCu, or to pivot to silicon bronze filler (ERCuSi-A) and treat the joint as a braze-weld rather than a fusion weld. The silicon and tin in those fillers act as deoxidizers and compensate for the oxygen in the base metal. More on that decision in the filler section below.

C10100 / C12200 — The TIG-Friendly Grades

C10100, known as Oxygen-Free High Conductivity (OFHC) copper, contains less than 0.0005% oxygen. It is the grade used in high-end electronics, vacuum tube components, and applications where conductivity and purity are paramount. C10100 TIG welds significantly better than ETP because the absence of oxygen eliminates the primary source of porosity and embrittlement.

C12200, or Deoxidized High Phosphorus (DHP) copper, contains phosphorus as a deoxidizer, which scavenges oxygen from the melt. It is the standard material for copper plumbing fittings and tubing and another reasonably TIG-friendly grade. When you are working with C10100 or C12200, your porosity risk drops considerably, though thermal conductivity and oxidation at the surface remain challenges that require the same approach to preheat, shielding gas, and filler selection.

If you cannot confirm your alloy designation, treat the material as ETP and choose your filler accordingly. Most commercial copper plate and bar stock sold without a specification is ETP.

Preheat and Amperage by Thickness

Copper TIG Settings Chart (1/16"–3/8")

The table below reflects standard practice for TIG welding pure copper and copper alloys on DCEN polarity. Preheat temperatures assume C10100 or C12200; if you are working with ETP copper, add 10 to 15% to the preheat temperatures shown to compensate for the additional energy loss from the oxygen content and to help with deoxidization. Amperage ranges assume a 2% ceriated or 2% lanthanated tungsten in good condition.

These are starting points, not absolutes. Copper's thermal conductivity means that long passes on a large workpiece will require amperage toward the top of each range or beyond it, because the part soaks heat away faster as the overall temperature of the workpiece rises. Monitor the puddle, not just the dial. If the puddle is sluggish and the arc is working harder than the metal is melting, you need more heat.

Preheat is non-negotiable above 1/8" thickness. Below that, you can sometimes manage with a very hot arc and fast travel speed, but any copper thicker than 1/8" will act as a heat sink that your torch simply cannot overcome from a cold start. Use an oxy-acetylene torch, induction heater, or propane rosebud to bring the part up to temperature before you begin, and verify with a contact or infrared thermometer.

Why DCEN for Pure Copper

DCEN, or Direct Current Electrode Negative, sends roughly 70% of the arc's heat to the workpiece and 30% to the electrode. For a metal that already demands maximum heat input, this polarity is the only practical choice. DCEN also produces a stable, focused arc that tracks well on copper's smooth, reflective surface.

AC polarity, which is used on aluminum, provides oxide cleaning action but reduces heat input to the work and introduces arc instability on copper. Copper does not form the same tenacious aluminum oxide layer, so the cleaning benefit of AC is irrelevant and the heat cost is significant. Always use DCEN for pure copper and copper alloys unless a specific process calls otherwise.

Shielding Gas — When Helium Is Worth the Cost

Pure Argon vs. Argon/Helium 75/25 vs. 50/50

Pure argon works well for copper up to about 1/8" thick. It produces a stable arc, flows at manageable rates of 15 to 20 CFH, and is the most affordable shielding option. On thin copper, pure argon provides enough heat input when combined with proper amperage and preheat.

At 3/16" and above, the argument for adding helium becomes real. Helium has a higher thermal conductivity than argon, which means the arc transfers more heat to the workpiece per unit of time. It also raises the arc voltage at a given amperage, effectively increasing the energy delivered to the puddle without requiring you to increase current further. On copper, where the workpiece is constantly stealing heat from the joint, this extra arc energy matters.

A 75% argon / 25% helium mix is the right starting point for copper between 3/16" and 1/4". The argon fraction preserves arc stability and reduces the flow rate you need compared to pure helium, while the helium fraction provides a meaningful boost in heat input. Increase your flow rate to 20 to 25 CFH with this mix to maintain adequate coverage.

A 50% argon / 50% helium mix is appropriate for copper at 1/4" and above, and especially for 3/8" material where preheat alone cannot fully compensate for heat loss into the base metal. The tradeoff is cost: helium is significantly more expensive than argon, and the higher flow rates this mix requires compound that cost. You will also need to increase flow rates to 25 to 35 CFH because the helium fraction reduces the gas density and shielding efficiency per cubic foot. For critical structural or electrical welds on heavy copper, the cost is justified. For occasional or short-run work, 75/25 at maximum amperage and preheat is often sufficient.

Pure helium is rarely necessary for TIG welding copper and is better suited to automated processes where its instability is managed by the equipment. Stick with argon/helium mixes for manual TIG work.

Gas Lens and Cup Sizing for a Hot Puddle

Copper at welding temperature oxidizes rapidly. The shielding gas column needs to cover not just the puddle but the heat-affected zone surrounding it, because any copper that gets hot enough to discolor is hot enough to oxidize. Standard collet-body setups, which produce a turbulent, narrow gas stream, are not adequate for copper's wide, hot puddle.

A gas lens replaces the standard collet body with a stainless mesh diffuser that produces a laminar, even shielding column. This laminar flow extends useful shielding coverage significantly beyond what a standard collet body delivers, protecting more of the surrounding hot copper and reducing oxidation in the heat-affected zone. On copper work, a gas lens is not optional equipment: it is part of the setup.

Pair the gas lens with a larger cup than you would use for the same thickness in steel. A #8 or #10 cup provides a shielding cone wide enough to protect the heat-affected zone on copper. Larger cups also allow you to run slightly lower flow rates without sacrificing coverage, which matters when you are already running higher flows for argon/helium mixes.

CK Worldwide's Gas Saver Kit includes a gas lens body and a range of cup sizes in a single package, making it straightforward to set up the large-cup, laminar-flow configuration that copper demands. The kit works across CK torch bodies and gives you the flexibility to swap cup sizes as thickness changes. For tight-access copper work, the Stubby Gas Saver Kit provides the same gas lens technology in a shorter configuration that keeps the cup closer to the joint.

Filler Metal Selection

ERCu (Deoxidized Copper)

ERCu is the AWS designation for deoxidized copper filler wire, which contains small amounts of silicon, tin, and manganese as deoxidizers. It is the correct filler for welding C10100 or C12200 copper where you want the finished weld to match the base metal's electrical and thermal conductivity as closely as possible. ERCu is available in 1/16", 3/32", and 1/8" diameters; choose a diameter that matches your tungsten size or one size smaller.

ERCu's deoxidizers help compensate for surface oxidation during welding and reduce porosity risk even on oxygen-free grades. If you are welding C11000 ETP copper with ERCu, the deoxidizing additions help but may not fully counter the base metal's oxygen content at higher thicknesses. You will still benefit from higher preheat and meticulous surface prep with ETP.

Pre-clean all copper filler rod with fine abrasive or a dedicated stainless brush before welding. Copper rod picks up surface oxides and contamination in storage that will translate directly to porosity in the weld if you skip this step.

ERCuSi-A Silicon Bronze — and When Braze-Welding Beats Welding

ERCuSi-A, commonly called silicon bronze, contains roughly 3% silicon and is technically a copper alloy filler rather than a pure copper filler. Its melting point is lower than pure copper, it flows extremely well, and the silicon content provides excellent deoxidizing action. These properties make it far more forgiving than ERCu when the base metal is ETP copper or when porosity is a persistent problem.

The tradeoff with ERCuSi-A is conductivity. Silicon bronze has lower electrical and thermal conductivity than pure copper, which disqualifies it for electrical connections where conductivity retention is critical. For structural copper joints, decorative copper work, or repair welds where conductivity is secondary, silicon bronze is often the better choice.

Silicon bronze also opens the door to a technique called braze-welding, where you keep the base metal below its melting point and use the filler's lower melting temperature to fill the joint by capillary action and wetting rather than full fusion. Braze-welding copper with ERCuSi-A requires less amperage than full fusion, reduces distortion, avoids the heat-sink battle with thick copper, and nearly eliminates porosity from base metal oxygen content because you are not fully melting the ETP copper. If you are joining ETP copper for non-electrical structural purposes, braze-welding with ERCuSi-A is often a smarter approach than fighting the physics of full fusion.

For C11000 ETP copper bus bars or conductors where conductivity matters, the correct decision is usually to evaluate whether TIG welding is the right process at all. Mechanical connections, bolted joints, or crimp connections often preserve conductivity better than any weld on ETP copper. When welding is required, ERCu with maximized preheat and meticulous deoxidization is the path forward.

ERCuAl-A2, or aluminum bronze filler, is used for welding copper-aluminum alloys and for surfacing applications. It is not appropriate for pure copper or silicon bronze base metals and should not be substituted for ERCu or ERCuSi-A on copper-to-copper joints.

Torch and Tungsten Setup for High-Amp Copper

Why You Need a Water-Cooled Torch

TIG welding copper at the amperages this metal demands is hard on torches. At 1/4" thickness, you are running 260 to 325A for long, sustained passes, and copper's thermal behavior means those passes are slow because you are constantly fighting heat loss into the base metal. Most air-cooled TIG torches are rated for 150 to 200A at a duty cycle of 35 to 60%. Sustained copper welding at 300A will exceed those limits and cook the torch body, damage the cable, and potentially fail at the worst moment.

A water-cooled torch eliminates this problem by circulating coolant through the torch head and cable continuously, removing heat at the source rather than relying on the surrounding air. For any copper work above 1/8" thickness that involves more than occasional short tacks, a water-cooled torch is the correct tool.

CK Worldwide's water-cooled torches, including the CK 20 series, handle up to 250A water-cooled and are designed for exactly the kind of sustained, high-amperage work that copper demands. The CK 20's compact head gives you access to joints without sacrificing the cooling capacity you need for long copper passes. Pair it with a water cooler sized appropriately for your amperage range, and you eliminate torch overheating as a variable entirely. For heavier copper at 300A and above, the CK 250 series provides the additional capacity that 3/8" copper and thicker sections require.

Tungsten Type and Grind for DCEN Copper

On DCEN, the electrode carries 30% of the arc's heat, which is manageable compared to AC but still significant at 300A and above. 2% ceriated tungsten (grey band) or 2% lanthanated tungsten (gold band, sometimes sold as LaYZr or similar designations) are the correct choices for DCEN copper work. Both maintain a sharp point at DCEN amperages, produce a stable, focused arc, and handle the high-heat environment better than pure tungsten, which is designed for AC aluminum welding and will degrade on DCEN at copper amperages.

Grind the tungsten to a sharp point for DCEN work, with a taper length of two to two and a half times the electrode diameter. A sharp point concentrates the arc and improves penetration, which matters on a material that is actively conducting heat away from the joint. Grind lengthwise on the tungsten, not radially, to avoid circumferential grind marks that can cause arc instability.

CK Worldwide's LaYZr tungsten is a 1.5% lanthanated electrode that covers the DCEN performance range needed for copper work. It starts easily, maintains a stable point, and handles the sustained high-amperage demands of copper passes without the tip degradation you get from pure tungsten on DC. Use it in the diameters specified in the settings chart above, matched to your amperage range.

Keep a dedicated tungsten for copper work. Contaminating a copper-used tungsten with aluminum residue from a previous AC session will cause immediate arc instability on your copper weld.

Pure Copper vs. Silicon Bronze — Head to Head

These two materials are often discussed interchangeably, but they behave differently enough that the comparison deserves a direct look before you commit to either.

Pure copper (C10100, C12200, or C11000) delivers maximum electrical and thermal conductivity, which is why it is used in bus bars, heat exchangers, and electrical conductors. It is also the most difficult material to TIG weld, requiring the most preheat, the highest amperage, the most careful shielding, and the most alloy-specific approach. The TIG process can produce excellent results on oxygen-free grades with the right setup, but it demands exacting preparation and the right equipment.

Silicon bronze (CuSi alloys) is a copper alloy that trades some conductivity for dramatic improvements in weldability. It flows easily, tolerates lower amperage, resists porosity, and can be braze-welded with far less preheat than pure copper fusion welding requires. Silicon bronze is the material of choice for artistic metalwork, marine hardware, sculpture, and structural copper-adjacent applications where electrical conductivity is not the primary specification.

If your application specifies copper for its conductivity, you must weld copper, and you must do it correctly using the settings, alloy identification, and equipment described in this guide. If your application uses copper for its appearance, corrosion resistance, or structural properties, silicon bronze is likely the better material and process choice. The finished weld will be more reliable, cleaner, and far less dependent on perfect setup conditions.

The decision point is simple: conductivity required means pure copper with proper setup; conductivity not required means silicon bronze is probably the smarter call.

Common Defects and Fixes

Porosity is the most common defect on copper TIG welds. It appears as small pits or voids in the weld face and cross-section. Porosity on copper almost always traces back to one of three sources: base metal oxygen content (ETP copper), contamination in the filler or base metal surface, or inadequate shielding gas coverage.

How to address porosity:

• Identify your copper alloy and switch to a deoxidized filler (ERCu or ERCuSi-A) if you are working with ETP.
• Clean the base metal and filler rod mechanically with a dedicated stainless brush and degrease with acetone before welding.
• Check your shielding gas flow and cup setup. A gas lens with a #8 or #10 cup at 20 to 25 CFH should eliminate coverage gaps.
• Increase preheat if porosity persists on thick sections, since a sluggish, incompletely molten puddle traps gas before it can escape.

Lack of fusion occurs when the puddle does not fully penetrate or bond to the base metal. On copper, this almost always means the base metal was too cold, either because preheat was insufficient or the part cooled down during a long weld. Increase preheat, weld faster to keep pace with heat loss, or add helium to your shielding gas to increase arc energy.

Cracking in copper welds is less common than in steel but can occur in the heat-affected zone of ETP copper due to grain boundary embrittlement from oxygen-hydrogen reactions. If you see cracking in or near the HAZ on ETP copper, switch your approach: use ERCuSi-A filler, consider braze-welding to reduce fusion depth, and maximize preheat to slow the cooling rate through the susceptible temperature range.

Oxidation and discoloration in the heat-affected zone are signs that your shielding coverage is insufficient. The fix is a larger cup, a gas lens, and higher flow rate as described in the shielding gas section. Post-weld oxidation, the dark, iridescent scale that forms on hot copper as it cools, is normal and addressed in the next section.

Arc wandering is often caused by a degraded tungsten tip or contaminated tungsten. Check your tungsten condition before blaming the machine. A sharp, clean ceriated or lanthanated electrode at the correct amperage for the diameter will track accurately on copper.

Post-Weld Cleanup and Property Retention

Copper oxidizes in the heat-affected zone during welding regardless of how good your shielding is, and the result is a dark, sometimes purple-to-black oxide layer that extends beyond the weld bead. For structural or decorative applications, this oxidation is primarily cosmetic. For electrical applications, it matters more.

To clean post-weld oxidation from copper, use a dilute citric acid or phosphoric acid solution applied with a brush, allowed to work for two to five minutes, then rinsed thoroughly with clean water. Mechanical cleaning with a fine abrasive pad or stainless wire brush works for accessible areas. Avoid harsh chloride-based cleaners, which can pit copper and accelerate corrosion in service.

For bus bars and electrical conductors, post-weld cleaning is critical to contact resistance. Oxide scale at a conductor joint increases contact resistance and generates heat in service, which is a safety concern in high-current applications. After cleaning, apply a thin coat of antioxidant joint compound (NO-OX-ID or equivalent) to any exposed copper surfaces at bolted or clamped joints before installation.

Electrical conductivity retention in a welded copper joint depends on the filler metal, the weld quality, and the absence of porosity. A properly made ERCu weld on C10100 copper will retain approximately 85 to 95% of the base metal's conductivity. A silicon bronze weld on the same material retains closer to 50 to 70%, which is why ERCuSi-A is not acceptable for bus bar connections in most electrical specifications. If your application has a conductivity specification, confirm your filler metal choice against that specification before welding.

Thermal property retention follows similar logic. Heat exchanger applications in copper require full-penetration welds with ERCu filler to avoid creating thermal bottlenecks at the joint. Any porosity, lack of fusion, or use of lower-conductivity filler in a thermal application will reduce efficiency at the joint.

Allow copper welds to cool slowly when possible. Quenching hot copper in water anneals it (softens it), which may or may not be desirable depending on the application. If the copper was work-hardened before welding, the heat-affected zone will be annealed regardless of cooling rate, so plan your joint location to minimize the impact of the softened zone on the structural design.

Setting Up for Success on Copper

Every element of a successful copper TIG weld connects back to heat management: identifying an alloy that can be fully fused, preheating to a temperature the material's conductivity demands, running enough amperage to maintain the puddle, shielding a wide, hot, oxidation-prone joint, and using a torch that can sustain the duty cycle without failing.

For water-cooled torch capacity at the amperages copper requires, CK Worldwide's CK 20 and CK 250 series torches are built for sustained high-amperage work. Pair them with a Gas Saver Kit or Stubby Gas Saver Kit for the large-diameter, gas lens-equipped cup setup that copper's oxidation demands, and LaYZr tungsten for stable, sharp-point DCEN performance across the full amperage range copper requires. The equipment does not compensate for poor setup, but the right setup becomes far more repeatable when the torch, gas coverage, and electrode are matched to what copper actually asks of them.