Protecting the car bottom from corrosion is not just a cosmetic procedure, but a vital necessity for extending the life of the body, especially in the harsh Russian climate. One of the most popular and time-tested means is a bitumen-rubber compound known as the "Cordon". However, many car owners face the problem of too thick consistency of the material immediately after opening the package, which makes it impossible to apply it qualitatively by spraying.
The correct decision of what to dilute the cordon directly affects the adhesion of the coating and its durability. Using inappropriate solvents or breaking proportions can cause the protective layer to crack, swell or simply not dry, turning into a sticky mass that collects dirt. In this article, we will discuss in detail the chemical composition of the material, the permissible types of diluents and the technology of preparing the mixture for work.
Analysis of the composition and selection of a suitable solvent
Before you start mixing components, you need to understand what material you are dealing with. The basis of mastic cordon It is bitumen reinforced with rubber and special modifying additives dissolved in organic solvents. It is the presence of an organic base that dictates the choice of diluent: it is categorically impossible to use water or alcohols here, since they will not react with bitumen, but only stratify the mixture.
The optimal choice for dilution is hydrocarbon solvents. Most often, the masters use White Spirit (Nefras-C4-155/200), which is ideal for bitumen mastics. It provides the necessary viscosity, evaporates slowly, allowing the material to spread evenly, and is not aggressive to rubber elements that can get into the treatment area. Solvent or kerosene are also allowed, but they require more caution due to the sharper smell and high volatility.
⚠️ Warning: Never use acetone, 646th solvent or Kalosha gasoline to dilute large volumes of mastic. Acetone evaporates too quickly, which will lead to the formation of bubbles and pores in the protective layer, and gasoline creates a fire hazard situation and can damage the factory LCP if accidentally hit.
It is important to take into account that different batches of the material can have initial viscosity, so the amount of solvent is selected individually. If you plan to apply the composition with a brush, it can be practically not diluted or a minimum amount of solvent can be added (about 5-10% by weight). To work with a spray gun or pneumosprayer, you will need a more liquid consistency, close to thick sour cream or even liquid yogurt.
Why can’t we use diesel fuel?
Some “old-timers” may advise diluting bitumen with a solar panel. This is dangerous: diesel fuel contains sulfur and other impurities that can eventually react with body metal or rubber components, causing accelerated corrosion under the mastic layer.
Mixing proportions and consistency calculation
The question of proportions is key to achieving a qualitative result. The manufacturer usually supplies a product ready for brush application, but adjustment is required for the sprayer. It is considered standard practice to add a solvent in a volume of 10% to 20% of the total weight of the mastic. The exact value depends on the ambient temperature and the diameter of the duse of your sprayer.
The dilution process should be gradual. Do not pour the entire volume of the solvent at once. Add the first portion (about 5-7%), mix thoroughly and check the viscosity. If the jet from the sprayer is intermittent or "spitting" with lumps, add a little more solvent. The ideal consistency is tested by experiment: the material should lie flat, glossy layer without undertone, but also not be too dry.
For clarity, consider the dependence of the amount of solvent on the method of application and temperature:
| Method of application | Air temperature | Recommended proportion of solvent | Target viscosity |
|---|---|---|---|
| Brush/Walik | +15...+25°C | 0-10% | Thick pasta |
| Pneumosprayer | +15...+25°C | 10-15% | Liquid sour cream |
| Pneumosprayer | +5...+15°C | 15-20% | Milk. |
| Airless application | Anybody. | 5-10% | Medium |
It is worth noting that when working in the cold season, the viscosity of the material naturally increases. In such cases thinner helps to compensate for thickening, but it is also important to remember the temperature of the cylinder with mastic. Cold material is worse mixed and dries longer, so before starting work, the container is recommended to be heated to room temperature.
Technology of surface preparation before treatment
Even a perfectly prepared solution will not stay on a dirty, rusty or moist surface. Preparation of the car bottom is the stage where 80% of all work is done. Before opening a cordon jar, a thorough car wash using active foam and Kercher to remove all road dirt, salts and bitumen stains is required.
After cleaning, the bottom should dry completely. The moisture under the layer of bitumen mastic can preserve the corrosion process, and the metal will rot from the inside, hidden from view. To speed up the process, compressed air or a heat gun can be used. Pay special attention to hidden cavities and spars, where water stagnates most often.
- 🧼 Carefully degrease the surface with antisilicone or white spirit to remove the residue of oils and improve adhesion.
- 🔧 Mechanically remove the detached rust with a metal brush or scraper if you plan to apply over the foci of corrosion.
- 🌬️ Blow all the process holes with compressed air to make sure there is no water in the hidden cavities.
If there are corrosion foci on the bottom that cannot be completely cleaned to metal, it is recommended to pre-treat them. rust converter. This chemical compound will convert iron oxides into stable compounds that can be covered with a protective layer. After drying the transducer (usually 2-4 hours), the surface is ready for application of the main anticores.
☑️ Checklist for bottom preparation
Application tools and safety techniques
The choice of tool is dictated by the scope of work and the desired quality of the coating. For local repair or processing of small areas, a rigid synthetic brush is quite suitable. However, for full anti-corrosion treatment of the entire bottom and arches, it is better to use pneumatic sprayer (pneumatic sprayer), connected to the compressor with a capacity of at least 200-300 liters per minute.
When working with solvents and bitumen compositions, it is extremely important to observe safety precautions. Organic solvent vapors are toxic and heavier than air, so they can accumulate in the bottom of a room or observation pit, creating a risk of poisoning or explosion. Work must be carried out in a well-ventilated room or in the open air.
⚠️ Note: Use a respirator with carbon filters and safety glasses. Drops of heated bitumen or aggressive solvent on the mucous membrane of the eyes can lead to serious burns, and prolonged inhalation of vapors causes headache and nausea.
Don’t forget to protect the brake discs, calipers and exhaust system elements. Mastic on the brakes will lead to loss of braking efficiency and boiling of the liquid, and on a hot muffler it simply burns, emitting suffocating smoke. All these nodes should be carefully closed with polyethylene or aluminum tape before starting work.
Use a diamond tip for a 2-3 mm diameter yatagan - it gives the optimal spray torch for thick bitumen mastics, providing a uniform coating without "spitting."
Deposition and drying of the protective layer
The application of the prepared composition requires uniformity. Hold the sprayer or brush at an angle of 90 degrees to the surface at a distance of 20-30 cm. Movements should be smooth, reciprocal. Don’t try to cover everything with a thick layer the first time – this can lead to material slipping (“tear effect”) and increased drying time.
The optimal technology involves the application of 2-3 layers. The first layer is primer: it is more liquid and penetrates into microcracks and metal pores. Subsequent layers are applied after the previous one has partially dried (usually after 30-60 minutes, when the surface ceases to be sticky on the stick). The total thickness of the dried film should be 250-400 microns.
The time of complete polymerization depends on the temperature and humidity of the air. At +20°C and normal humidity, the surface dries up in 12-24 hours, but full polymerization and strength gain take up to 3-5 days. During this period, it is not recommended to operate the car, especially in wet weather or on dirty roads, so as not to damage the fresh surface.
- 🖌️ Apply the material in cross movements so as not to miss any area.
- ⏱️ Keep the interlayer drying according to the instructions on the package (usually 1 hour).
- 🌡️ Do not work in the direct sun or at temperatures below +5 ° C, as this will disrupt the process of evaporation of the solvent.
Pay special attention to the hidden cavities of the rapids and spars. For their processing, special spray nozzles with a 360-degree torch are used, which are introduced through the process holes. The inner cavities are treated before material appears in the adjacent holes, which ensures the volume is completely filled.
The quality of corrosion protection depends on the surface preparation 90% and only 10% on the properties of the material itself. Poorly cleaned rusty metal under the expensive composition will rot as quickly as without it.
Common Errors and How to Resolve Them
In the process of self-processing, car owners often make mistakes that negate all efforts. The most common of these is saving on solvent or using inappropriate substances, as mentioned above. Another common mistake is applying mastic to wet metal, which triggers hidden corrosion.
Another problem is the insufficient thickness of the layer in hard-to-reach places and, conversely, the formation of "leaks" on flat surfaces. If you notice that the material has flowed, do not immediately try to wipe it with a cloth - you will only smear the bitumen. Wait until it dries a little, and carefully cut the excess with a spatula, after which iron out the transition place with a brush with a small amount of solvent.
Sometimes, after drying, craters or “shagrene skin” appear on the surface. This may be due to the ingress of silicone or oil on the surface before painting, or too rapid evaporation of the solvent (for example, in a draft or at high temperature). In such cases, the defective area must be cleaned, degreased and re-layed.
Can you mix the cordon with other anticores?
It is strictly not recommended to mix bitumen mastics with compositions based on wax, oils or water. Chemical incompatibility can lead to coating dissection, loss of elasticity and flaking. If you decide to change the type of anticores, the previous layer must be completely removed mechanically or chemically.
How long does Cordon dry before the car wash?
Although the surface film is formed in a day, it takes 3 to 7 days for all volatile fractions to be fully polymerized and evaporated. You can wet the coating after 24 hours, but aggressive washing under high pressure is recommended no earlier than a week after application.
Do I need to warm a can with mastic before use?
Yes, if the material temperature is below +15°C. Warm mastic mixes better, penetrates the pores more easily and requires less solvent to achieve working viscosity. You can warm in warm water (up to 40-50°C), but never use an open fire because of the fire hazard of vapors.
How to wash Cordon off your clothes or skin?
Fresh spots are removed with white spirit, kerosene or special asphalt stain cleaners. Frozen bitumen from clothes is almost impossible to wash. From the skin of the hands it is better to use vegetable oil or oily cream, so as not to overdry the skin with aggressive chemistry, and then wash off with warm water and soap.
How to store the remainder of diluted mastic?
Residues of the material should be stored in tightly closed containers, eliminating contact with air. The neck of the can can be turned upside down so that the resulting film serves as an additional cover. The shelf life of the diluted composition is less than the original, so try to spend it during one season.