Tin bronze and copper wire rod are routinely conflated on RFQs because both ship in shiny coils, but they answer completely different questions: tin bronze is an alloy (Cu plus 4-12% Sn plus optional Zn/Pb) selected for sliding wear and seawater resistance, while wire rod is a feedstock product form (typically 8 mm or 3/8 in hot-rolled coil, ~150 kg/mm² as-rolled) drawn into magnet wire, building wire, and welding consumables [S1][S3].
Buck Copper lists tin-bronze rod, bar, sheet, foil and tube alongside electrolytic copper, brass and silicon-bronze stock, confirming the two families sit in different catalogue lines [S1]. Specifying one as the other — for example calling a CuSn6 bushing "wire rod" or buying ETP wire rod for a bearing — is one of the most common errors a process engineer catches on the shop floor.
Composition and Designation: Alloy Family vs UNS-Numbered Wire Stock
Tin bronze is defined by tin as the principal alloying element, typically C90300-C91700 in UNS / C903-C917 in DIN-cum-old-EN (e.g. CuSn12 = C90810 territory), with common wrought grades C51000 (5% Sn, phosphor bronze A) and C52100 (8% Sn, phosphor bronze C), and cast grades such as C90300 (88-10-2 Cu-Sn-Zn) used for bushings and gear blanks [S2]. Hardness climbs with tin: C51000 annealed sits around 60-80 HB and can exceed 180 HB after cold work, while cast C90300 typically tests 70-90 HB.
Wire rod, in contrast, is a product form — almost always ETP (C11000, 99.90% Cu min) or fire-refined high-conductivity (FRHC) — melted and continuously cast, then hot-rolled to an 8 mm (0.315 in) or 3/8 in coil typically weighing 1.5-4 t, used as feedstock for drawing [S1][S3]. Drawing it down 0.05-0.30 mm gives magnet-wire conductor; drawing to 0.6-1.2 mm with a CuSn alloy overlay gives Cusi3mn1 or ERCuSn-A welding wire for MIG/TIG overlay of bronze parts [S3].
Mechanical and Physical Targets: Strength vs Conductivity
Tin bronze is bought for sliding wear, fatigue strength, and corrosion resistance, not conductivity. Tin-bronze bushings typically operate at PV (pressure × velocity) limits of 40-70 MPa·m/min for moderate-lubrication service, with C90300 fatigue strength around 150-180 MPa. Conductivity is intentionally sacrificed: C90300 sits at 12-15% IACS versus 100-101% IACS for ETP copper [S2].
Wire rod is bought for drawability and conductivity. ETP C11000 coil at 8 mm feeds drawing lines producing 0.05-0.50 mm magnet wire at 60-100% IACS after anneal, with intermediate anneals at 380-450 °C. Even EcuA1-A2 (low-fuming brass welding rod) — a related copper-alloy wire — ships at 5.60-5.80 USD/kg in 10 t lots out of Tongling, a price point tied to alloy cost, not conductivity [S5].
Selection Criteria: Five Gates That Separate a Tin-Bronze Buy From a Wire-Rod Buy
Gate 1: Is the part a sliding or wear component, or a conductor? Bushings, sleeves, worm gears and pump impellers route to tin bronze grades; motor windings, earthing conductors and transformer leads route to wire rod. [S1]
Gate 2: Required conductivity. Anything above 50% IACS rules out tin bronze (C51000 ≈ 18% IACS, C90300 ≈ 12-15% IACS) and forces ETP / OF copper rod. Below 25% IACS is the comfortable tin-bronze range.
Gate 3: Service environment. Seawater, sour service, and acidic condensate push the call toward tin bronze; tin-bronze C90300/C90500 has decades of marine-pump and valve-trim service because SnO₂ surface film stabilises in chloride media [S2].
Gate 4: Section size and form. Bearings are cast sand or centrifugal cast (10-50 mm wall), or hot-extruded rod, while wire rod arrives as 8 mm hot-rolled coil at 1.5-4 t master. Buying a 1 t coil of C51000 and machining bushings is technically possible but uneconomical versus centrifugally cast tube.
Gate 5: Post-process. If the part will be drawn further or stamped into fine wire, wire rod is the only rational buy; if the part will be machined, cast, or extruded into bar, tin bronze is the natural buy.
Real Use Cases: Where Each Material Wins in 2026 Sourcing
Tin bronze remains standard for industrial bushings, bridge bearings, pump housings, and worm gears — service classes where a steel alternative would gall, and where leaded variants C93200 / C93700 add free-machining performance [S2]. The bioon.com mechanical-engineering dictionary still records cast-bronze test results showing tin-bronze substitutes for ZQSn-grade bushings "the alloy costs less than tin-bronze ZQSn" — useful only as a price benchmark, not as a free pass to drop Sn in a sliding service.
Welding-wire variants are themselves alloyed wire rod: ERCuSn-A (CuSn6 overlay), ERCuAl-A1/A2 (aluminium-bronze, for marine and ship repair), ERCuSi-A (silicon-bronze MIG/TIG of brass and galvanised steel), and low-fuming RbCuZn-C brass brazing rod at 5.60 USD/kg / 10 t minimum order [S3][S5].
Standards, Limits and Common Failure Modes
Tin-bronze chemistry follows ASTM B505 / B584 for cast and ASTM B139 for wrought rod/bar; mechanical properties of C90300-C91700 cast bars are bounded by ASTM B22 / B584, and wrought phosphor-bronze strip by ASTM B103. Tin-bronze heat-treat window is narrow — full anneal at 550-650 °C with rapid cool to avoid the brittle δ-phase (Cu₃₁Sn₈) at 350-580 °C, a phase engineers avoid because it cuts ductility and impact strength. [S2]
Wire rod is governed by ASTM B49 (continuous cast ETP/FRHC copper rod for electrical purposes), EN 1977 (copper and copper alloy drawn rod), and for magnet-wire feedstock ASTM B3 / B174 / B738. A typical 8 mm ETP coil must reach 99.90% Cu min, 0.040% O max, 100-101% IACS, and elongation ≥30-35% in 200 mm. Failure modes differ: wire rod cracks under back-pull when oxygen exceeds 0.04% (OF-copper route) or when intermetallics carry through from the cast bar; tin bronze fails by dezincification if the Zn ratio is mis-set, or by pitting in stagnant seawater if Sn drops below 4%.
Cost, Lead Time and 2026 Sourcing Signals
Price gaps are real: bare ETP wire rod (8 mm coil) sits in a tight band tied to LME copper plus a small conversion premium, while low-fuming brass welding rod lists at 5.60-5.80 USD/kg in 10-50 t truckload orders out of Tongling/Anhui, and ERCuAl / ERCuSn welding wire runs higher due to alloy content [S5]. Tin-bronze bushings are cast-to-order (sand, centrifugal or continuous cast), so 4-8 weeks lead time is common versus 1-3 weeks for a stocked wire-rod coil.
For a related read on how hard gates discipline a copper-alloy buy from the moment an RFQ lands, see stud-welder-versus-circular-saw for the same decision-tree discipline on a different shop floor. For projects that pair a bronze-bushing pump with a welded galvanised pipe, tank-cleaning-machine-buying-guide covers the geometry and pressure of the tank the bushings will live in.
Two trackable signals close this out: (1) LME 3-month copper and tin spread — when the Sn premium widens, foundries push designers toward C90300-lean (low-Sn) variants and back toward brass/bronze hybrids; (2) update revisions to ASTM B49 (continuous-cast wire rod) and ASTM B505 (tin-bronze sand castings) — these standards shift every 3-5 years and a buy referencing a 5-year-old revision may fail incoming inspection. A sourcing engineer who logs both signals every quarter stays ahead of mis-quoted orders.
For component-level specifications, see draw wire sensor.