Bare Al-Si rod
Solid 4047, 4045 or 4343 rod used with separate flux paste or powder. Most flexible and lowest cost; suits torch brazing of 1xxx, 3xxx and 6063 parts.
Brazing filler metals
Aluminium Brazing Rods for HVAC, Repair and Production
Aluminium brazing rods are filler metals that melt below the base metal and are drawn into the joint by capillary action, giving neat, leak-tight joints with far less heat than welding. The main families are aluminium-silicon rods (4047, 4045, 4343, 4145) brazed at roughly 570 – 620 °C, and zinc-aluminium rods that work around 380 – 480 °C for repairs and copper-to-aluminium joints. Metline supplies bare, flux-coated and flux-cored rods in standard and custom sizes, worldwide.
- Al-Si rods
- ≈ 570 – 620 °C
- Zn-Al rods
- ≈ 380 – 480 °C
- Diameters
- 1.6, 2.0, 2.4 mm; others to order
- Standards
- AWS A5.8 · ISO 17672
How aluminium brazing rods work
Brazing joins metals with a filler that melts above 450 °C but below the base metal. The base metal never melts, so distortion is low, thin walls survive and dissimilar metals can be joined. Aluminium is harder to braze than copper or steel for two reasons: its tough oxide film must be removed by flux (or by vacuum and magnesium), and the gap between filler and base-metal melting points is small.
That small gap is why choosing the right rod matters. Al-Si fillers melt from about 577 °C, while common base alloys such as 3003 begin to melt around 640 °C and 6063 around 615 °C. A torch or furnace has to bring the joint into that narrow window. Zinc-aluminium rods melt much lower, which makes them easier to use by hand and safer for heat-sensitive or higher-alloy parts, at the cost of lower joint strength and corrosion resistance.
Strictly, fillers that melt below 450 °C are solders, so most low-temperature "aluminium brazing rods" sold for repair are technically high-temperature solders. The distinction matters when a specification calls for brazed joints.
Types of aluminium brazing rod
Flux-coated rod
Al-Si rod with an external flux coating, so no separate flux is needed. Convenient for maintenance and field work; protect from moisture.
Flux-cored rod
An aluminium sheath with flux sealed inside. Flux releases steadily as the rod melts, giving consistent results in semi-automatic and production torch brazing.
Al-Si-Cu rod (4145)
Copper lowers the melting range (about 521 – 585 °C), giving a little more margin on lower-melting base alloys. Joints are less corrosion resistant than plain Al-Si.
Zn-Al rod
Zinc-aluminium alloys melting around 380 – 480 °C, often flux-cored. Used for HVAC copper-to-aluminium joints, repair of thin sections and patching.
Preforms
Rings, washers and discs of the same alloys for production joints. See our brazing rings and preforms.
Aluminium-silicon brazing alloys
These are the fillers specified in AWS A5.8 and ISO 17672 for aluminium brazing. Melting and brazing ranges are approximate and vary slightly within the composition limits.
| Alloy | AWS / ISO | Si % | Approx. melting range | Approx. brazing range | Best for |
|---|---|---|---|---|---|
| 4047 | BAlSi-4 / Al 112 | 11 – 13 | 577 – 582 °C | 582 – 604 °C | Most fluid; general torch and furnace brazing |
| 4045 | BAlSi-5 / — | 9 – 11 | 577 – 591 °C | 588 – 604 °C | Furnace (CAB) brazing; clad layers |
| 4343 | BAlSi-2 / — | 6.8 – 8.2 | 577 – 613 °C | 599 – 621 °C | Thin parts where erosion must be limited |
| 4145 | BAlSi-3 / — | 9.3 – 10.7 + 3.3 – 4.7 Cu | 521 – 585 °C | 571 – 604 °C | Slightly lower brazing temperature |
Check the solidus of your base alloy: it should be comfortably above the top of the brazing range. 1100, 3003 and 6063 are easy; 6061 (solidus about 582 °C) is borderline; 2xxx and 7xxx alloys are generally not brazeable with Al-Si fillers.
Zinc-aluminium rods for low-temperature work
| Alloy type | Approx. melting range | Typical use | Notes |
|---|---|---|---|
| Zn-Al eutectic (≈ 5 % Al) | ≈ 382 °C | Repair rods, thin aluminium, die-cast patching | Very low heat input; joints are weaker than Al-Si |
| Zn-15Al | ≈ 382 – 450 °C | Copper-to-aluminium HVAC tube joints | Wider range helps fill gaps |
| Zn-22Al | ≈ 420 – 480 °C | Cu-Al joints needing more strength | Requires matching non-corrosive or cesium flux |
Zinc-rich joints are anodic to aluminium and especially to copper, so in wet or salty service they can corrode preferentially. Seal or coat Cu-Al joints in outdoor units. For more detail see brazing aluminium to copper.
Choosing a flux
| Flux type | Active range | Residue | Use with |
|---|---|---|---|
| Chloride-based (corrosive) | ≈ 450 – 620 °C | Corrosive; must be washed off | Torch brazing with Al-Si rods; repair work |
| Potassium fluoroaluminate (non-corrosive) | ≈ 565 – 610 °C | Non-corrosive, can stay on part | CAB furnace brazing; flux-cored Al-Si rods |
| Cesium-modified fluoride | Lower activation | Non-corrosive | Zn-Al rods; Mg-containing base alloys |
Flux-cored and flux-coated rods remove the guesswork of applying flux, but they still need clean, degreased joints. Heavy oxide, paint and oil must be removed before brazing. Our aluminium brazing flux guide covers the chemistry in more depth.
Rod sizes and packing
Standard supply
- Diameters
- 1.6 mm, 2.0 mm and 2.4 mm; other sizes on request
- Lengths
- 330 mm and 500 mm straight lengths; custom lengths on request
- Construction
- Bare, flux-coated or flux-cored
- Packing
- Small retail packs, 0.5 kg and 1 kg industrial tubes, or custom OEM packing
- Labelling
- Alloy, AWS/ISO classification where applicable, size and lot number
Torch-brazing aluminium: step by step
- Check the base alloyConfirm its solidus is well above the rod’s brazing range. Avoid 2xxx and 7xxx alloys.
- CleanDegrease and remove oxide with a stainless brush or abrasive just before brazing.
- Fit upAim for a joint gap of roughly 0.05 – 0.25 mm and fixture parts so they cannot move.
- FluxApply flux to both surfaces, or use a flux-cored or coated rod.
- Heat evenlyUse a soft, neutral flame and heat the thicker part first. The work, not the flame, should melt the rod.
- Feed and finishTouch the rod to the joint when flux turns liquid; let capillary action draw it in. Cool, then wash off corrosive flux residue.
Rod selection by application
| Application | Typical rod | Why |
|---|---|---|
| HVAC copper-to-aluminium tube | Zn-Al flux-cored | Low temperature protects thin aluminium tube and avoids brittle Cu-Al phases |
| HVAC aluminium-to-aluminium repair | 4047 flux-cored or Zn-Al | Clean, leak-tight joints with controlled heat |
| Radiators and oil coolers (repair) | 4047 / 4045 with fluoride flux | Matches the original brazed construction |
| Windows, doors, gutters, furniture | Zn-Al or 4047 flux-coated | Low distortion on thin extrusions |
| Production torch brazing | 4047 flux-cored or preforms | Consistent flux delivery and filler volume |
| Castings and die-castings | Zn-Al | Many castings have low solidus or porosity that Al-Si heat would aggravate |
Common mistakes to avoid
- Brazing high-strength alloys such as 2011, 2014, 2017, 2024 and 7075; they melt locally or lose strength. Use mechanical joints or welding procedures designed for them
- Melting the rod with the flame instead of the workpiece, which leaves unbonded filler on the surface
- Leaving chloride flux residue, which causes corrosion months later
- Overheating thin sections, which erodes or melts the base metal
- Using zinc-rich rods on parts that will be anodised; zinc joints anodise poorly and discolour
References and standards
- AWS A5.8/A5.8M – Specification for Filler Metals for Brazing and Braze Welding
- ISO 17672 – Brazing: Filler metals
- AWS C3.7 – Specification for Aluminum Brazing
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits
- ASM Handbook, Volume 6A – Welding Fundamentals and Processes (brazing of aluminium alloys)
Aluminium (aluminum) brazing rod: frequently asked questions
What temperature do aluminium brazing rods melt at?
Al-Si rods such as 4047 melt at about 577 – 582 °C and are used up to about 604 °C. Zinc-aluminium repair rods melt at roughly 380 – 480 °C depending on composition.
Which rod should I use for copper to aluminium?
A zinc-aluminium rod, usually flux-cored, because its low working temperature protects the aluminium and limits brittle copper-aluminium compounds. Seal the joint against moisture.
Do I need flux to braze aluminium?
Yes, except in vacuum brazing. Use separate flux with bare rod, or choose flux-coated or flux-cored rod.
Can I braze 6061 aluminium?
With care. 6061 starts to melt around 582 °C, which overlaps the Al-Si brazing range, so lower-temperature 4145 or Zn-Al rods with tight temperature control are safer. Strength in the heated zone will drop.
Why is brazing not recommended for 7075 or 2024?
Their melting ranges start too low and their strength depends on heat treatment that brazing destroys, so joints crack or the base metal melts.
What sizes do you supply?
Standard rods are 1.6, 2.0 and 2.4 mm in 330 or 500 mm lengths; custom diameters, lengths and packing are available, shipped worldwide.
Need aluminium brazing rods?
Tell us the base metals, joint type, heating method and quantity. We will recommend a rod and confirm a delivered price.
