Harris Silicon Bronze TIG GTAW Welding Rod (.045 in × 36 in, 10 lb Box — 03SIBH0) is a copper-based TIG filler metal classified under AWS A5.7 as ERCuSi-A. Silicon bronze filler metal — nominally 94–96% copper with 2.8–4.0% silicon, plus small additions of manganese and zinc — is uniquely suited for TIG welding copper and copper alloys, for braze welding thin-gauge galvanized steel, and for dissimilar metal joints between copper and steel. The .045 in (1.14 mm) diameter is a medium-sized TIG rod that provides a balanced deposition rate for structural silicon bronze work — heavy enough to span gap variations in brazed or braze-welded joints, yet controllable enough for fine work on thin-wall tubing and sheet.
Harris Products Group (a Lincoln Electric company) has manufactured ERCuSi-A silicon bronze filler metal since the company's founding — it remains one of the most widely specified copper-alloy filler metals in HVAC, plumbing, automotive, and artistic metalworking. The finished weld deposit has a distinctive golden-copper color, excellent ductility, and corrosion resistance superior to carbon steel, making silicon bronze TIG joints the preferred choice when aesthetics and corrosion resistance of the weld zone are visible requirements.
- AWS Classification: ERCuSi-A per AWS A5.7/A5.7M
- Copper: Balance (~94–96%)
- Silicon: 2.8–4.0%
- Manganese: 1.5% max
- Zinc: 1.0% max
- Tin: 1.0% max
- Iron: 0.50% max
- Aluminum: 0.01% max
- Diameter: .045 in (1.14 mm)
- Rod Length: 36 in (914 mm)
- Package: 10 lb box
- Tensile Strength (as-welded): ≥50,000 psi (345 MPa)
- Yield Strength: ≥20,000 psi (138 MPa)
- Elongation: ≥15%
- Melting Range: 1,580–1,630 °F (860–888 °C)
Harris .045 in silicon bronze TIG rod is the preferred choice in all braze-welding and copper-alloy TIG applications where the joint requires ductility, corrosion resistance, and a finished weld appearance that complements the base metal:
- Braze Welding Thin-Gauge Galvanized Steel: HVAC ductwork, automotive sheet metal repair, and galvanized structural panels. At 1,580–1,630 °F, silicon bronze melts below the zinc burn-off temperature, allowing braze welding of galvanized sheet without fully destroying the zinc coating on the adjacent material — greatly extending corrosion protection at the joint compared to autogenous MIG welding.
- Copper Water Pipe and HVAC Copper Tubing: TIG braze-welding ACR copper tubing (ASTM B88) with silicon bronze for HVAC refrigerant circuits, plumbing manifolds, and hydronic heating systems. The ERCuSi-A deposit is copper-colored and inherently corrosion resistant in water service, matching the appearance of the parent copper.
- Artistic and Decorative Metalwork: Sculptors and architectural metalworkers use silicon bronze TIG rod to join bronze, brass, and copper with the matching golden deposit color. The ductile, easily-chased deposit accepts grinding, sanding, polishing, and patina chemicals identically to traditional cast silicon bronze.
- Silicon Bronze Casting Repair: Sand-cast and investment-cast silicon bronze components (ASTM B584, Alloy C87300, C87600) are repaired with ERCuSi-A TIG to restore dimensional accuracy without post-repair heat treatment — the alloy's single-phase structure is not susceptible to HAZ cracking.
- Copper to Mild Steel Braze Welding: Joining copper bus bars, terminals, or conductors to steel structures with a ductile, conductive silicon bronze bead. The deposit provides adequate strength for light structural applications and the copper-rich chemistry resists galvanic corrosion at the dissimilar metal interface better than steel filler metal alternatives.
- Stainless Steel Sheet Braze Welding: Used at lower heat input on 304 and 316 stainless sheet when autogenous TIG welding would cause distortion — the lower liquidus temperature of ERCuSi-A (1,580 °F) versus austenitic stainless (2,550 °F) allows deposits to be placed with minimal heat input and distortion.
Silicon bronze can be applied by GTAW (TIG), GMAW (MIG), or oxy-fuel welding. TIG with ERCuSi-A offers the finest control over puddle temperature and bead placement — essential when working on thin-gauge sheet or making precision braze welds on copper tubing. GTAW is the preferred process for .045 in rod.
- Process: GTAW, DCEN (copper-alloy TIG work is performed on DC, not AC — copper does not form a refractory oxide like aluminum)
- Preheat: 200–300 °F (93–149 °C) for copper base metal over 1/4 in to offset copper's high thermal conductivity. Light-gauge work (under 1/8 in copper) typically requires no preheat — the TIG arc provides adequate localized heat.
-
Amperage:
- Light gauge (0.049–0.065 in copper sheet): 50–80 A
- Medium gauge (0.083–0.120 in): 80–120 A
- Heavy gauge (3/16–1/4 in copper plate): 120–180 A
- Galvanized steel sheet (18–14 ga): 60–100 A (lower heat to minimize zinc fume)
- Tungsten: 2% ceriated (grey) or 2% lanthanated (gold/black), 3/32 in diameter for most silicon bronze TIG work. Grind to a sharp taper for DCEN.
- Standard: 100% Argon at 15–25 CFH. Argon produces clean, bright copper-colored deposits with good puddle control.
- Alternative for braze welding galvanized: 75% Ar / 25% He to increase fluidity and improve wetting on galvanized surfaces at slightly lower arc temperature — reducing zinc vapor emission versus pure Ar TIG at the same amperage.
- No CO₂ — CO₂ additions to shielding gas cause surface oxidation of copper-based weld metal and are not used with copper-alloy TIG filler.
For braze welding galvanized steel, do not allow the base metal to reach full melting temperature — keep the arc on the filler rod, not on the base metal, and let the copper-silicon deposit flow onto the preheated steel surface via capillary/wet-out action. This "braze welding" technique melts the filler but not the base metal, preserving adjacent zinc coating and minimizing zinc oxide fume. Use respiratory protection (N95 minimum or supplied air) when braze welding galvanized steel — zinc oxide fume causes metal fume fever.
- Store in original packaging in a dry, clean location. Copper-based TIG rod does not absorb moisture the way aluminum rod does, but surface oxidation (green or blue-green tarnish) increases arc instability and bead discoloration.
- Handle rods with clean gloves — copper alloys are sensitive to phosphorus and sulfur contamination from skin perspiration, which can cause hot shortness and porosity in the weld deposit.
- Inspect rods for uniform bright copper or golden color. A light tarnish is acceptable and can be removed by wiping with clean acetone-dampened cloth. Heavy green or black tarnish indicates advanced oxidation — replace affected rods for critical or food-contact work.
- Keep silicon bronze rod physically separate from steel TIG rod in storage. The copper-colored rod is visually distinctive but should be labeled separately to prevent misapplication (using steel TIG rod on a copper base metal would create a galvanically active, brittle joint).
Harris ERCuSi-A .045 in TIG rod is compatible with any DC TIG welding machine. Lincoln Electric platforms commonly used for copper alloy and braze-welding TIG work:
- Lincoln Precision TIG 225 (K2533-1, DCEN mode, well-suited for copper-alloy current ranges)
- Lincoln Square Wave TIG 200 (DCEN mode)
- Lincoln Dynasty 200 DX (low-amperage DCEN for thin copper work)
- Lincoln PTA-17, PTA-17V TIG torches (preferred for the 50–150 A range typical of silicon bronze TIG work)
Primary base metals:
- C110 (ETP copper), C101 (OFHC copper), C102 water-pipe copper (ASTM B88, B68, B75)
- Silicon bronze castings (ASTM B584, C87300, C87600)
- Galvanized steel sheet (ASTM A653, all zinc coating classes)
Secondary base metals:
- Brass (C220–C280 series) — flux may be needed; consult Harris braze selection guide
- Carbon steel to copper dissimilar joints (braze-welded with silicon bronze)
- 304 and 316 stainless steel (low-heat braze welding application)
Q1: What is the difference between braze welding and brazing with silicon bronze?
A: Brazing (capillary brazing) uses a thin gap (0.002–0.005 in) and relies on capillary action to draw filler metal through the joint by heating the base metal near its melting point. Braze welding uses a wider groove or gap and deposits the filler metal directly into the joint in layers, similar to fusion welding — but without fully melting the base metal. Silicon bronze TIG rod is most often used for braze welding (groove joints, fillets). For capillary copper brazing on tube fittings, a paste or ring brazing alloy is the standard choice, not TIG rod.
Q2: Can I use ERCuSi-A silicon bronze to weld pure copper pipe?
A: Yes — ERCuSi-A is the standard TIG filler for autogenous welding of copper water pipe (ASTM B88). For 3/4 in and smaller pipe in typical plumbing service, silicon bronze TIG produces a strong, water-tight joint. For large-diameter copper pipe (>2 in) or high-pressure service, consult the applicable plumbing code (IPC, UPC, ASME B31.3) for the approved joining method — some codes require certified brazed joints using BCuP-type filler for pressure-rated copper piping.
Q3: Is ERCuSi-A appropriate for welding bronze castings?
A: Yes — ERCuSi-A TIG rod is the standard repair filler for silicon bronze castings (C87300, C87600). The composition closely matches the parent casting and deposits a single-phase (alpha) deposit that can be machined, chased, and finished to match the surrounding casting surface. No post-weld heat treatment is required for most repair applications. For very large repairs or structurally critical castings, consult the casting foundry for their repair weld procedure.
Q4: What safety precautions are needed when braze welding galvanized steel?
A: Zinc oxide fume is released when zinc-coated steel is heated above 900 °F. Inhalation causes metal fume fever — flu-like symptoms (fever, chills, nausea, headache) appearing 4–8 hours after exposure. Required precautions: (1) use a NIOSH-approved N95 particulate respirator at minimum; P100 or supplied-air respirator preferred; (2) use high-volume local exhaust ventilation (LEV) positioned directly at the weld; (3) never braze-weld galvanized in confined spaces without supplied air; (4) consume milk or electrolyte drinks post-weld — folk remedy but widely practiced; (5) rest if symptoms develop 4–8 hours after welding.
Q5: Can silicon bronze TIG rod be used on stainless steel?
A: Yes — silicon bronze is used for braze-welding thin-gauge 304 and 316 stainless steel when distortion control is paramount. The lower deposition temperature (~1,580 °F vs. the 2,550 °F melting point of stainless) puts far less heat into the stainless base metal, dramatically reducing distortion and warping on thin sheet. The joint strength (~50 ksi tensile) is lower than an autogenous stainless TIG weld, so this technique is appropriate for non-structural, aesthetically visible joints in stainless where distortion is the critical design constraint.
Q6: What causes black smut on silicon bronze TIG welds?
A: Black smut on copper-alloy TIG welds is silicon dioxide (SiO₂) scale from oxidation of the silicon in the filler metal. Primary causes: (1) shielding gas coverage is insufficient — check flow rate (increase to 20–25 CFH) and inspect for hose leaks or drafts; (2) post-flow time too short — increase post-flow to 6–8 seconds; (3) arc length too long — keep arc length to approximately 1 wire diameter; (4) CO₂ in the shielding gas — switch to 100% Argon. The silicon oxide is not harmful but must be removed before additional passes (use a stainless wire brush) to prevent inclusions.
Q7: What is the corrosion resistance of a silicon bronze TIG weld compared to the copper base metal?
A: ERCuSi-A deposits have corrosion resistance very close to that of pure copper and copper-silicon alloys in atmospheric, freshwater, and mild marine service. The silicon addition actually improves corrosion resistance in acidic environments compared to pure copper. The weld zone will darken and patina at approximately the same rate as the surrounding base metal when exposed to weather, making silicon bronze TIG repairs and joints virtually invisible after a few months of outdoor exposure.