This paper describes a technology developed by the Bureau of Mines that permits the soft-solder fabrication and repair of aluminum and aluminum alloy substrates and assemblies. The process involves electrodeposition of a thin ni-cu alloy coating on the zincated aluminum substrate. This coating induces standard sn-pb solders to wet and spread when using standard fluxes. Solder joints so formed are relatively corrosion resistant and equivalent in strength to joints formed on copper or brass using the same solders and fluxes. The ni-cu alloy (30 to 70 pct ni) coating is electrodeposited from buffered acetate electrolyte by electrolytic cell (more suitable for initial fabrication) or by brush-coating (more appropriate for repairs). The method has also been used to soft-solder aluminum and aluminum alloys to copper and brass. In general, the process appears applicable for any reactive substrate that will accept an adherent ni-cu-alloy coating. A variety of potential uses for fabrication and repair of items such as heat exchangers, electrical components, and energy conversion systems are envisioned for the soldering process.