How to solder a stainless steel to a stainless steel? How to solder with a rosin and tin soldering iron

How to solder a stainless steel to a stainless steel using tin and rosin? This is a very time-consuming process, for the implementation of which you need to know all the subtleties and tricks of soldering work. If you follow the instructions in this article, you can make a reliable connection of stainless steel products.

Process features

For work with food containers, only lead-free solders (for example, tin and alloys based on it) can be used. Soldering stainless steel products is a complex process that requires some knowledge and skills. The best solder for working with the mentioned metal is tin. Thanks to this material, you can make a quality connection. However, tin is often used for soldering in the case when you need to attach small parts or repair small cracks. Solder is sold in coils or in the form of bars 2–4 mm thick.

In industry, tin soldering is rarely used. And at home, to repair household items (for example, a stainless steel kettle), use a soldering iron or gas burner, as well as the mentioned solder. In this case, the main thing is to prepare the necessary consumables (consumables). But we should not forget: during soldering, hot objects and toxic substances will be used, therefore, safety rules must be observed.

Why is flux needed?

rosin in the picture

This substance will ensure uniform spreading of solder on the surface of the soldering zone and will create conditions for high-quality adhesion of the material to the metal coating. Fluxes are currently classified by the degree of impact on the following varieties:

  1. Inactive (neutral), in which there are no acids. In addition, they almost do not conduct electric current.
  2. Active (acidic) fluxes.
  3. Protective (anticorrosive), the purpose of which is to protect the soldering zone of the finished joint from corrosion and destruction.

If the question arises, why do we need a flux for soldering, then we can answer this way: this substance is necessary for observing the technology, since it will definitely be needed during soldering work. However, the method of applying the composition depends on its initial state:

  • if the flux is in a solid state, the tip of the soldering iron must first be dipped into the reagent, and then grab a little solder;
  • the finished liquid mixture will have to be applied to the soldering zone with a brush;
  • the paste substance should be treated with a conventional stick.

In addition, flux is sometimes sold in special tubes.

Necessary fixtures

The picture shows a 100 V soldering iron

Before proceeding with the repair of the product, you need to prepare such tools and materials:

  • A simple soldering iron (minimum power - 100 watts) or a propane torch.
  • Organic solvent (e.g. white spirit or acetone).
  • Tin solder.
  • Rosin or phosphoric acid.
  • Steel rope.
  • Metal brush, file or sandpaper.
  • Clean a cleaning cloth.

However, before you solder the stainless steel to the stainless steel and, accordingly, repair the part, you should purchase protective equipment: polyurethane gloves, glasses and a respirator. In addition, to connect large products, you may need a more powerful soldering iron, the tip of which should be fireproof: this will not only increase the service life, but also increase the technical parameters of the tool. As for the solder, it should also be said that tin bars are suitable for soldering food utensils or other containers, since they contain less harmful impurities.

How to solder with a rosin and tin soldering iron : technology

stainless steel soldering

When the materials and tools are prepared, you can begin this operation. To perform the soldering of stainless steel at home, you need to follow this step-by-step instruction:

  1. To clean a metal surface from an oxide film and a pollution with an emery cloth or a brush.
  2. Degrease the component to be repaired with solvent.
  3. Apply flux - rosin or soldering acid to the treated surface. This step does not need to be performed if a combined tin solder is used, which already contains the substance in question. It is necessary to apply the flux immediately before the soldering, since a film forms on the surface of the stainless steel after about 10 seconds.
  4. Preheat the soldering zone, on which the flux is applied, with a tin-plated soldering iron tip.
  5. Add solder if necessary, but the first time, most likely, cover the entire surface with tin will not work.
  6. Reapply the flux and reheat it with a soldering iron. Repeat this process until the metal surface is covered with a uniform layer of tin. The main thing is that the solder does not melt from the tip of the soldering iron, but from the heat stored in the part. In addition, to make the soldering of stainless steel with tin better, you need to add rosin to the joints, due to which oxides from the solder will be removed.
  7. Wash the product from flux residues. To complete this step, you need to prepare a solution consisting of water and detergent, and buy metal scrapers. Residues of rosin, according to the masters, are well cleaned with cold water, since the substance in it becomes brittle.

Soldering is considered to be of high quality if the result is a uniform surface. But in any case, at the end, the coating must be sanded with sandpaper or a file.

sealed frame

How to connect stainless parts: the best technique

First you need to equip the workplace. The table should be steel or have a non-combustible surface. The main thing is that it is smooth. In addition, you need to make high-quality exhaust ventilation. In turn, in order to solder several products into one at home, it is necessary to cover their parts with tin and fix between them. The next step is to heat the parts at the same time so that the hot solder connects. Probably, tin will have to be added to the soldering zone, depositing it on the tip of the soldering iron.

After that, you need to warm up the entire surface and, if the solder is laid down qualitatively, you need to put the parts on a flat surface. A stainless steel product assembled from two or more parts cannot be moved until the joints are completely solidified. It is better to fix the soldered parts with fixing devices (for example, clamps or a vice).

Gas soldering: kettle repair

gas soldering

First you need to thoroughly clean the soldering area with sandpaper and descale near the damaged area. To solder a stainless steel kettle with a gas burner, you need to follow this instruction:

  1. Warm the connection with flame, gently moving the device. Heating will be sufficient when the solder begins to melt from contact with the metal.
  2. Apply flux (rosin or phosphoric acid) to the soldering area.
  3. Put tin on the damaged area, while continuing to heat the area with a burner so that the substance, when melted, fills the entire defective area.
  4. Grind the seam with a brush for metal.
  5. Wipe the sealed area with alcohol to clean its surface from scale and oxides.

During soldering, you need to monitor the oxygen level. To determine this parameter, you need to look at the flame, the normal shade of which is blue. In a supersaturated composition, the color will be pale, which indicates an excess of oxygen. If you ignore this requirement, it is likely that the stainless steel will begin to oxidize.

soldering process

Benefits of Tin Soldering

The advantages of this method include the following properties:

  • supplies are inexpensive;
  • long preparation of the part is not required;
  • simple soldering work for small items;
  • tin solder reduces the fluidity of stainless steel when soldering;
  • good connection quality.


In addition to the indisputable advantages, soldering stainless steel using tin solder has some disadvantages:

  • difficulty in sealing seams on inclined and vertical planes caused by high fluidity of tin;
  • insufficient strength of one-piece joints for large structures;
  • reduction of the allowable temperature range of sealed parts due to the fact that the tin will simply melt if the material is exposed to a temperature of more than 231.9 ° C.


Naturally, without a good soldering iron and flux, you cannot make a reliable connection. However, before you solder a stainless steel, you need to take into account other points:

  1. It is advisable to buy a soldering iron with a sting that does not burn: the life of such a tool is longer than that of a conventional device. However, it must be constantly descaled and sharpened. In addition, it is recommended to use a soldering iron with constant heating: this will save energy.
  2. Soldering a stainless steel without a flux is a bad idea, since an oxide film will constantly appear.
  3. Inexperienced craftsmen should practice a little on unnecessary details and trimmings. You need to remember: a reliable connection is difficult to tear off, and you can check its quality with a screwdriver or awl.
  4. A solvent treated part can only be touched with gloves, since a small stain left on the surface can ruin the entire work.
  5. Before soldering a stainless steel to a stainless steel, it is necessary to provide the room with good ventilation. In addition, do not touch the heated metal or solder with your hands, or inhale toxic fumes.
  6. Tanks with substances must be closed immediately after use with a tight lid.
  7. The finished part must be cleaned of flux and solder composition. Food containers are treated with soapy water and boiled to neutralize aggressive acids.
soldered part

Main mistakes

If, taking into account the recommendations, it still failed to make a high-quality connection, then such a failure may occur due to:

  • poor metal stripping and poor degreasing;
  • insufficient heating of stainless steel;
  • incorrect solder or flux;
  • the fact that the soldered part was subjected to mechanical stress too early, because the product did not have time to harden.


The article examined how to solder a stainless steel to a stainless steel. To perform the described work, you need to purchase the necessary equipment and devices. During soldering work, the main thing is to make high-quality seams that will provide the parts with a reliable connection. In addition, thanks to the information provided in this article, anyone can repair small stainless steel products on their own using a soldering iron, tin solder and flux.


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