Corrosion of metal elements of the body is the main enemy of any car, which eventually turns strong steel into loose mass. Many car owners face a situation where the external signs of rust appear long before the body parts lose their integrity. One of the most effective methods of prevention and restoration of damaged areas is tinderIt creates a strong barrier between the aggressive environment and the base metal.
This process is often confused with soldering, but tinting has its own unique features, consisting in applying a thin layer of molten metal to the surface without filling gaps or joining parts. Tin-lead or lead-free solders, penetrating into the microscopic pores of the metal, block the access of oxygen and moisture to the steel base. Properly executed treatment allows you to significantly extend the life of body elements, especially in areas of increased risk, such as rapids, arches and bottom.
Work in garage conditions requires not only certain skills, but also strict adherence to surface preparation technology. A critical step is the complete removal of the oxide film and degreasing, as even a microscopic layer of fat will negate the solder adhesion. In this article, we will discuss all the nuances of the process, from the selection of materials to the finishing so that you can protect your car with quality.
The essence of the process and the choice of materials for servicing
Beading is the process of coating the surface of the product with a layer of molten tin or its alloys. In the context of auto repair, this is used to create an anti-corrosion layer on body parts. The main difference from soldering is that the base metal does not melt and is not deformed, but is only covered with a protective film. For work most often used lead-tank PIC stamps, where the figure indicates the percentage of tin.
Choosing the right solder directly affects the durability of the coating and its resistance to mechanical damage. Sales with a high tin content are more plastic and better resist corrosion, but have a lower melting point. On the other hand, alloys with the addition of lead provide greater coating hardness, which is important for the bottom and arches exposed to abrasive effects of sand and stones.
- 🧪 POS-40 Universal solder with a melting point of about 235 ° C, great for most bodywork.
- 🧪 POS-61 - contains more tin, has better electrical conductivity and corrosion resistance, but softer.
- 🧪 Leadless solders An environmentally friendly option, often with the addition of silver or copper, requiring higher temperatures.
- 🧪 Fluxes. - an essential component for the removal of oxides, most often used orthophosphoric acid or zinc chloride.
Do not forget that the quality of the flux plays no less a role than the solder itself. Orthophosphoric acid It is ideal for working with steel, as it not only cleans the surface, but also creates a protective film of phosphates. The use of aggressive acids such as salt acids is strictly prohibited, as they can cause deep corrosion of the metal under the solder layer.
Necessary tool and workplace preparation
For high-quality performance of tinting, it is not enough just to have solder and flux; a specific set of tools is needed to control temperature and evenly distribute the material. The main tool is a powerful soldering iron or gas burner. Conventional household soldering irons for 40-60 W will not work here, as they will not be able to heat up massive body parts to the required temperature.
The best solution is to use an electric soldering iron with a capacity of 250 W or a small gas burner with an adjustable flame. Gas burner is preferable for large areas, as it allows you to quickly heat up the metal, but requires caution not to overheat the steel and not cause its release (loss of strength). You will also need metal brushes, sandpaper of various grains and personal protective equipment.
⚠️ Warning: Working with open fire and molten metal requires the mandatory use of protective glasses and heat-resistant gloves. Flux and solder vapors are toxic, so provide powerful ventilation in the room.
Preparation of the workplace should include the presence of a fireproof coating on the floor and nearby surfaces. Sparks or drops of melted solder can easily burn through the mats or damage the paintwork of the neighboring parts of the car. Prepare the rags in advance to remove excess flux and a solvent to clean the tool.
☑️ Checking the servicing readiness
Technology of body surface preparation
The success of the whole event depends on the quality of surface preparation 90%. The metal should be absolutely clean, dry and defatted. Any residue of paint, primer, rust or dirt will cause the solder to simply roll off the surface or, worse, to peel off after a short time. Start the process by mechanically cleaning the damaged area.
Use a grinder or P80-P120 sandpaper to remove loose rust and old coating. Your job is to get to the pure, shiny metal. After mechanical cleaning, the surface must be thoroughly degreased. For this, specialized antisilicones or ordinary acetone are excellent. Rub the surface with clean rags until the traces of dirt cease to remain on the napkin.
After degreasing, the chemical processing stage begins. Put it on. orthophosphoric acid or another suitable rust converter to the prepared area. This will remove microscopic residues of oxides that are not visible to the eye and create a rough structure for better adhesion. The exposure time depends on the acid concentration and is usually 15 minutes to an hour, after which the surface is washed with water and thoroughly dried.
It is important to understand that between degreasing and the beginning of tinting should not take much time to metal did not have time to cover a new oxide film. If you work with large areas, work them in stages. A perfectly prepared surface should have a matte gray hue without visible defects.
What to do if the rust is through?
If you find through corrosion during the sweep, puddles alone will not help. In this case, you must first install a metal patch or use fiberglass with epoxy glue, and only then hunch the surface to protect against the external environment.
Body soldering process
After the surface is prepared, you can proceed to the most important stage - the application of solder. Heat the soldering iron or burner to working temperature. If you use a soldering iron, its sting should be stained and clean. Apply a thin layer of flux to a small piece of metal you plan to process. Do not flux the entire detail at once, as it may dry or become contaminated.
Bring a hot soldering iron stinger or burner flame to the surface of the metal, simultaneously touching the solder bar. The metal must warm up to such an extent that the solder begins to melt from its heat, not just from contact with the tool. This will ensure good spreading and penetration into the pores. The movements shall be smooth, distributing the molten metal in a uniform thin layer.
| Parameter | Optimal value | Impact on outcome |
|---|---|---|
| Sting temperature | 300-350°C | Insufficient temperature will not allow to spread, excess will burn flux |
| Seed layer | 0.1.0.3 mm | A thick layer can break off on impact, a thin one will not protect |
| Time of contact | 2-5 seconds | Prolonged heating of one point leads to deformation of the metal |
| Inclination angle | 45 degrees. | Optimal angle for spreading and controlling the process |
If solder rolls into balls and does not stick, this is a sure sign of poor surface preparation or insufficient warming. In this case, you need to stop working, clean the problem area again, apply a fresh flux and try again. Quality tinting is characterized by a smooth, shiny layer, which is firmly held on the metal.
Use a wooden spatula or spatula to level the solder if it lies in uneven lumps. Wood does not stick to tin as much as metal and helps distribute mass.
Handling of hard-to-reach places and seams
Particular attention is required by welded seams, joints of panels and internal cavities, where corrosion is most often born. The grazing of these zones requires increased accuracy and the use of tools with a curved sting or special nozzles on the burner. The main task is to ensure the penetration of molten solder into the microcracks of the weld, where the paint does not penetrate.
When working with seams, it is recommended to use more refractory solders that provide greater mechanical strength of the connection. The movement of the instrument should be directed along the seam, with a slight pressure to squeeze excess flux and air bubbles from under the solder layer. This will prevent the formation of voids in which moisture can subsequently condense.
For the inner surfaces of the sills and spars, special methods are used, such as stretching the solder rod through the technological holes with simultaneous heating from the outside. However, this method requires high qualification, as there is a risk of burning through a thin metal or damage neighboring elements. In such cases, aerosol compounds with a high content of zinc are often used as an alternative to hot tinting.
⚠️ Warning: When servicing near plastic elements, rubber seals or glass, be sure to cover them with asbestos sheets or metal screens. High temperatures can instantly melt plastic or break glass.
Finishing and protection of the coating
After tinting and cooling of the metal is completed, the surface must be thoroughly washed with warm water with the addition of an acid neutralizer (such as a soda solution) to stop the chemical reactions. Flush residues are hygroscopic and can cause corrosion under the solder layer if not removed. After washing, the part should dry completely.
Clean tin coating looks aesthetically pleasing, but it is quite soft and subject to mechanical damage. Therefore, for final protection, it is recommended to apply a layer of soil or a special anticorrosion composition. If the tin was carried out on visible parts of the body for subsequent painting, it is necessary to use soil compatible with tin, since some types of primers can react with non-ferrous metals.
For hidden cavities and bottoms, an excellent solution would be to apply bitumen mastic or wax preservative over the tin layer. This will create a double barrier of protection: chemical (tin) and mechanical (mastic). Regular inspection of such areas will allow you to notice the damage to the protective layer in time and restore it before the corrosion processes begin.
The stain is not a decorative coating. For the durability of the result, it must be covered with soil, paint or mastic, depending on the location of the part.
Can I hum a galvanized body?
You can galvanize galvanized surfaces, but this requires special care. Zinc has a lower melting point than steel and can burn out when overheated, depriving the metal of galvanic protection. In addition, the adhesion of tin to zinc is worse than to pure steel. It is recommended to use special fluxes for galvanizing and strictly control the heating temperature, preventing redness of the metal.
How to replace orthophosphoric acid?
If orthophosphoric acid is not available, soldering acid (zinc chloride) can be used, but it is much more aggressive and requires perfect subsequent washing. There are also special flux pastes for soldering steel, which are less active but safer for the metal. The use of traditional methods, such as aspirin, for bodywork is not recommended due to low efficiency in large areas.
How long does the stain cover last?
If the technology is followed and the finishing protective layer (paint, mastic), the tin coating can serve for decades, actually throughout the life of the car. Tin itself does not rust and protects steel electrochemically. However, if the protective top layer is damaged to the metal, corrosion may begin at the chip site, although it will spread more slowly than on unleaded steel.