Tin-Zinc Solders for Soldering Aluminum and Other Metals

Johnson's family of tin-zinc alloys for soldering aluminum are referred to as "Alumaweld" solders, a trade id that goes back to the early thirties. Alumaweld Solders have many uses:

#1 is the only alloy in this family that contains lead, 40% by weight. It is used most often for the repair of cast iron, either with or without a flux.

Johnson's #2 Sn/25Zn, #20 Sn/20Zn, and another alloy, Sn/30Zn, are generally supplied in wire form for thermal spray applications.

Our #21 is the eutectic composition, Sn/9Zn that melts at 390° F (199 C). This relatively low temperature enables its use for soldering thin aluminum materials, or for pretinning temperature or flux sensitive aluminum parts to be later joined in another step.

#22 Alumaweld starts to melt at 390° F also, however it is not completely liquid until it reaches 635° F (335 C). When used with flux, its wide plastic range is better suited to soldering heavier materials and wider joint clearances. Johnson is a leading supplier of tin-zinc solders to the capacitor, plating and thermal spray industries.

Alumaweld alloys may be used with Johnson's Alumasol Organic Soldering Flux, or our more aggressive Alumweld 2000 Inorganic Chloride Flux. Alumaweld solders may also be used to "swage," abrade or mechanically clean the surface without using the chemical cleaning action of a flux. Swaging is effective only because of the zinc content in Alumaweld solders. Zinc is an element made up of hard, sharp-edged crystals that aid in abrading (scrubbing) through the tough aluminum oxide layer, thus permitting the metallurgical reaction between the filler and base metals to occur.

View our Technical Bulletin for application tips.

Alumaweld Alloys
Alloy Composition Solidus°F Liquidus°F Shear PSI Typical Uses
#1 Sn/20Zn/40Pb 335 635   Cast iron repair
#2 Sn/25Zn 390 580   Aluminum
#20 Sn/20Zn 390 535   Aluminum
#21 Sn/9Zn(e) 390 390 4177 Aluminum
#22 Sn/40Zn 390 635   Aluminum
  (e) - eutectic alloy