General Characteristics

The surface of aluminum and its alloys is covered by a tough oxide film due to its light oxidation behavior, which makes soldering difficult. An additional difficulty is that the soldering points are prone to corrosion. Soldering can be facilitated by plating copper or nickel on aluminum in advance. Places of soldering are etched with sulfuric acid, caustic soda solution, followed by rinsing in water, and then subjected to nickel plating or copper plating in the galvanic bath. Surfaces covered with a film of nickel or copper are soldered with ordinary soft solders. But the electroplating method is complicated, time consuming and quite expensive. Usually, they simply strip the edges before soldering and use special solders for soldering aluminum - most often technically pure zinc. When soldering by rubbing it gives a joint strength of about 9 kg/mm², but such joints corrode quickly. Solder one and solder two give a tensile strength of at least 10 kg/mm². Solder three is particularly ductile and has considerable relative elongation; its strength limit is about 8 kg/mm². Solder four is prone to brittleness, but gives a joint strength of up to 20 kg/mm². Note that the strength of the solder joint increases as the melting temperature of the solder increases.

Percentage composition of solder for aluminum and its alloys

Composition of fluxes and solders

Rosin, stearin, powdered sugar are used for fluxes. Preliminary solder is rubbed on the surface with a brush or scraper. For overlap connections sometimes powdered zinc chloride is used as a solder. Powder of dry zinc chloride is poured on the surface cleaned for soldering and heated. The zinc chloride melts, releasing acrid smoke. As a result of the exchange reaction, aluminum combines with chlorine and evaporates, and molten zinc fuses with aluminum, penetrating the surface layer. In this way, the aluminum surface is skinned with zinc, and the parts are joined by the zinc-aluminum alloy.

Optimization

Heating of the overlapped and annealed parts gives them a strong connection that is resistant to corrosion. Stronger brazing requires more refractory brazing alloys and special fluxes. A special solder for aluminum, for example, consists of 25-30% copper, 4.7% silicon and the rest aluminum. The solder melts at 525 °C and is used together with a flux of lithium chloride 25-30%; potassium fluoride 8-12%; zinc chloride 8-15% and potassium chloride - the rest. The flux melts at 450 °C. This solder and flux provides a strong soldering of aluminum.

Buy, price.

Evek GmbH has a wide range of fluxes and solder at optimal prices in its warehouse. We offer favorable delivery terms for wholesale and retail customers. On our site you will find all the necessary information, at your service experienced consulting managers who are always ready to help with the choice. Product quality is guaranteed by strict compliance with the rules of production at all stages. Delivery times are minimal. Preferential discounts are available for bulk orders.