Aluminum is a common metal that combines many remarkable qualities, including a high thermal conductivity with a relatively low weight. But this material, which is in demand in everyday life and in production, has one significant drawback - it easily reacts with other elements. This property significantly complicates the soldering of car cooling radiators, for example, and also leads to difficulties when it is necessary to weld a heating battery.
Is it possible to solder aluminum radiators
Due to the activity of aluminum, there is always a film of oxides on its surface, which prevents it from combining with other metals. Therefore, soldering radiators based on it for most car owners and ordinary users is a very serious problem.
It is possible to obtain a high-quality and reliable connection of aluminum with another metal only after heating the contact point to a high temperature.
In the process of heating the surface, a layer of protective oxides is also formed, which does not allow soldering even a small structural element to it. Therefore, when soldering this metal, special fluxes are used to remove the film from the processing site. They include bismuth, cadmium or zinc. Only with their help it is possible to clean the surface of the welded metal and make it accessible to working solders.
The cost of branded fluxes with guaranteed quality can be too high. For this reason, home craftsmen prefer to make such compositions (fluffs) on their own. Subject to the proportions indicated in the instructions, do-it-yourself solders are not inferior to proprietary compositions and sometimes surpass them in terms of effectiveness.
What is used for soldering
On the market, consumables are represented by standard bars of the TsOP-40 brand, according to GOST, having the following composition:
- tin;
- zinc;
- aluminum;
- silicon and copper.
The elements included in the solder (especially zinc) ensure high strength of the resulting joint, and also guarantee its anti-corrosion protection. With its help, it is possible to solder small structural elements and large parts of aluminum radiators.
Soldering procedure
The correct organization of the aluminum soldering procedure requires thorough preparation, without which it will not be possible to achieve the desired result. Before you solder the radiator yourself, you should carefully read the corresponding instructions. It indicates that the preparatory stage includes cleaning the restored zone and preparing the soldering composition of the required quality.
Preparatory operations
Before soldering the aluminum radiator with a rosin-based flux, prepare the damaged area according to the following instructions:
- Remnants of the old coating and traces of dirt are removed.
- The soldering area is cleaned with an abrasive.
- Immediately thereafter, it is degreased with a solvent.
Before soldering the radiator, you will need to prepare the flux in a metal crucible in advance. To do this, the rosin is first melted with a gas burner, after which small iron filings are added to the melt, taken in a 1: 2 ratio (they perform the function of an abrasive). At the same time, the prepared composition is mixed until a homogeneous mass is achieved.
The materials used for brazing are toxic and emit toxic fumes hazardous to humans. Therefore, all operations are carried out in the presence of a hood or in the open air. If it is impossible to fulfill these conditions, a working person will need a respirator.
Elimination of small defects
- The soldering iron picks up a small amount of solder.
- In circular smooth movements, it is applied to the place previously treated with flux.
- During processing, it is important to ensure that the solder layer is distributed over the surface as evenly as possible.
When soldering, the sawdust contained in the solder removes the oxides from the surface, and the rosin added earlier blocks the oxygen access channel. As a result, all conditions are created for obtaining reliable contact between different metals. This method is only suitable for small lesions that do not exceed a few millimeters. On large areas, the flux cools down quickly and does not provide good heating of the soldering point.
Recovery of significant damage
The need to restore large areas of aluminum surfaces is encountered quite often. You will need a special soldering compound called "flux". Before using it, the surface of the battery to be treated is prepared, as was done for small areas.
Initial components for the preparation of fluff:
- potassium and lithium chlorides;
- common table salt;
- sodium sulfate;
- cryolite.
The mixture prepared in a certain proportion is first thoroughly ground in a mortar to a state of powder. After that, it is poured into a crucible, where it is thoroughly mixed until a homogeneous mass is suitable for obtaining a melt.
If the resulting powder is not immediately used for work, it is poured into a suitable container, closed with a tight stopper, and stored in a dark place.
Soldering procedure using flux:
- The damaged area is thoroughly heated with a gas burner.
- A portion of the fluff is applied to the prepared place with a thin layer.
- The damage is soldered with tin-lead solder with the addition of small amounts of bismuth.
When working with special equipment (gas burner), it is important not to overheat the restored area, so as not to burn it. The strength of the flame is selected so that it is sufficient only for uniform heating of the surface of the aluminum product.
Repair of complex radiators
There are situations when it is required to restore (unsolder) an aluminum radiator of a car, which has many hard-to-reach places. In this case, methods based on the use of iron-rosin flux and self-prepared flux are not suitable. Thin-walled tubes of a copper or brass car radiator, for example, are very difficult to solder due to the design. In this situation, it is recommended to use low-temperature solder (LTS) with simultaneous gluing of the restored surface.In the list of the considered preparatory operations, the need to crimp the damaged section of the radiator or stove with pliers should be added, which will reduce the size of the hole.
In the course of soldering, the treated area is first thoroughly heated with a gas burner, after which an NTP bar is introduced into its flame. Periodically passing them along this place, you need to try to make sure that the solder particles cling to the edges of the damage and gradually "tighten" it. At the final stage, it will be necessary to seal the defect zone using a special high-temperature glue for this. With its help, it is possible to "patch up" all the remaining minor irregularities and flaws.
Using cold welding and glue
When you need to repair a minor damage or patch up a small chip on the surface of a part, it is best to use an adhesive called "cold welding". It is a special mixture with a high degree of plasticity and made on the basis of epoxy resin - a polymer with unique strength characteristics. In addition, the composition of "cold welding" includes various fillers (sulfur and plasticizers), which further increase this indicator.
Most often, it is produced in the form of two plastic bars, which outwardly resemble children's plasticine. Before use, they are simultaneously kneaded with fingers, as a result of which the desired mixture of two components is obtained. To glue the damaged area, it is enough to separate a small piece of the crushed mass and apply it to a previously prepared surface.
Any of the methods for restoring aluminum radiators can be realized without the help of unauthorized persons. However, if you are not completely confident in your own abilities, it is best to contact a specialized car repair shop.
