Alumite™ - Fluxless Aluminum Solder and Diecast Solder Rod

Kapp Alumite™ fluxless Aluminum soldering & brazing rod for the fabrication, maintenance and repair of cast Aluminum and Zinc alloys. Alumite™ has been used and endorsed by leading cast Aluminum, diecast and white metal manufacturers for over 60 years!!!


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Benefits and Uses

Actual cast Aluminum solder applications result in joints that are permanent, non-corrosive and, in many cases, stronger than the parent metal. Alumite™ will join most Aluminum alloys, Zinc-based alloys, pot metal, and white metal. It can also be used as a general purpose high strength solder.

Fluxless Aluminum Soldering with Alumite™

To solder Aluminum, the invisible oxide film must be penetrated by the solder to obtain metal-to-metal bonding. This can be done simply and effectively without chemical flux by scratching the Aluminum surface using the Alumite™ rod.


Pre-Tinning the Joint Surface

  1. Heat the area to be soldered to a temperature that will melt the end of the solder stick as it scratches across the heated Aluminum surface. DO NOT OVERHEAT!
  2. The solid end of the solder stick first punctures and loosens the oxide layer and allows the solder to flow underneath.
  3. Continue to apply the solder to the entire surface to be joined.
  4. Repeat this process on the other surfaces to be joined.

Many types of repair and construction are possible using this fluxless technique; however, the Aluminum surfaces must be accessible to stroking/scratching by the Alumite™ solder rod. The solder will not flow by itself into a narrow (capillary) joint. To promote capillary action, the Alumite™ companion flux Kapp Lunar™ Flux is required.

T - Joints

For maximum strength, Pre-Tin the joint area of both members as described above and bring together. Heat the parts and flow a fillet of solder into the intersection. Fillets are made by running the solder stick along set-up members where contact is desired. Let the heat from the members, NOT THE FLAME, melt the solder. Run the solid end of the solder stick through the molten fillet to remove any trapped oxide. In many cases, adequate strength can be obtained without pre-tinning. However, when the members are not pre-tinned, the fillets alone support the joint load, as the members are not joined to each other, but only to the fillets.

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Butt Joints

Ends of the Aluminum parts are beveled and brought together. Follow the pre-tinning procedure, stroking both beveled surfaces of the joint with Alumite™.

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Lap Joints

Parts can be pre-tinned and slid together while the solder is still molten. Alternatively, a generous fillet of solder can be applied to the edges of the lap joint, making sure of strong bonding by running the stick through the molten solder. If the joint surfaces are not properly pre-tinned, or accessible to scratching with the Alumite stick, Kapp Lunar™ Flux is required to draw the solder into the lap joint.

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Mitered Joints

(Windows, Doors, Screens, Frames)

Members should be solidly jigged. Leave a sufficient gap between parts for the solder to flow and bond (1 to 4/1000ths of an inch - .001 to .004). A neutral flame is played over the joint area until the Alumite™ melts when drawn across the joint. Make sure of solder to part bonding by drawing the solid end of the solder stick through the molten solder deposit. After joining, the joint may be built up and finished as desired. These joints are stable in high humidity and have remained in perfect condition after many years of exposure.

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Repair and Change Design of Aluminum Match Patterns and Dies

The section to be worked should be cleaned by filing or grinding, and then tinned by heating the Aluminum to a temperature that will melt the solder stick rubbing the surface. WHEN APPLYING ALUMITE™, THE ALUMITE™ STICK SHOULD ALWAYS BE KEPT OUT OF THE FLAME. Build up the material with a soft flame. Pre-heating the entire match plate of the die to approximately 600°F facilitates this procedure.

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Welding Zinc Based Castings

Remove any plating, natural oxide, or foreign matter from the surfaces to be joined. "V" out the fracture and set up the job solidly. Use #1 or #2 tip to preheat the area surrounding the fracture. The joint is then made by heating the fracture directly with a neutral flame until the SURFACE of the base metal can be broken by touching it with the Alumite™ rod. KEEP THE ROD AWAY FROM THE FLAME AS MUCH AS POSSIBLE WHEN STARTING THE WELD. Continue welding the fracture by puddling the solder in the base metal. NEVER PLUNGE INTO WATER TO COOL. Finish as desired.

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Welding White Metal

Clean plating and scale from the surface to be welded. "V" out the fracture and set up the job solidly. Preheat generally with a neutral or acetylene flame. Heat directly until the parent metal begins to melt, and then dip the solder rod in and out of the molten puddle until the desired buildup is reached. NEVER PLUNGE INTO WATER TO COOL. Finish as desired.

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Repairing Stripped Threads

Drill the old threads out over size, so that when the new fillet is added all the drilling and tapping will be done in Alumite™. This will make it easier to work with and will increase strength. After drilling, heat the base metal from the bottom of the hole up. Scratch the rod along the wall of the hole and fill, beginning at the bottom and work up. Fill the hole, cool, drill and tap as needed.

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Excellent Capillary Action Using KAPP LUNAR™ FLUX

For blind joints, complicated assemblies, or automatic and furnace soldering where Alumite™ can not be manipulated to remove oxides, KAPP LUNAR™ FLUX is required to draw the solder into the joint. The fluxing action is very rapid, and when the correct temperature is reached the solder will melt and be drawn under the oxide layer.

This capillary action is so pronounced that it is possible to draw the solder between two pieces of Aluminum, even when both pieces are in a vertical position. After pieces have cooled thoroughly, flux residues must be removed with hot water. One trick that can help capillary action between two parts is to heat from one side and apply the flux from the other. In a vertical joint, heat from the bottom and apply flux and solder from the top. This ensures that the heat just reaches the desired temperature to activate the flux and flow the solder. When the flux begins to boil and the solder stick starts to melt, remove the heat. Residual heat from the part will melt the stock and draw the solder into the joint.

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Alumite™ Physical Properties & Technical Data
Melting Range715F - 735F / 379C - 391C
Tensile Strength39,000 psi
Compression Strength60,000 to 75,000 psi
Shear Strength34,000 psi
Impact Strength (Charpy)4 ft.lbs. to break 1/4" bar
Hardness (Brinell-500 kg. load)100
DuctilityGood
Density.25lbs./cu. in.
Elongation3% in 2 inches
Linear Expansion Coefficient15.4 x 106 / F
Electrical Conductivity24.9 (%IACS)
Thermal Conductivity.24 cal / cm3 / C
Corrosion Penetration300 x 106 in 1 1 / R
FluxNone on Accessible Joints
Kapp Lunar™ Flux where needed
MIL SpecificationsMeets MIL-R4208

*Note: Shear strengths based on double lap joints, Tensile strengths depend on base metals, soldering methods and type of joint.

Standard Sizes And Packaging

Size Length Packaging
1/8" 9" 25 or 50 Lb Plain Bulk
1/8" 12" 25 or 50 Lb Plain Bulk
1/8" 18" 25 or 50 Lb Plain Bulk
3/16" 18" 25 or 50 Lb Plain Bulk
3/16" 36" 50 Lb Plain Bulk
1/4" 18" 25 or 50 Lb Plain Bulk
1/4" 36" 50 Lb Plain Bulk

We cannot ship 36" lengths via UPS or FedEx ground due to potential damage in transit. These boxes must be on pallets.