Corrosion is a silent but merciless enemy of any car, and it is the sills that become its first victims. Moisture mixed with reagents and road dirt accumulates in hidden cavities, triggering irreversible processes of metal destruction. Many owners notice the problem too late, when the paint on the outside has already swollen and through holes have formed inside. To extend the life of the body, you need professional anti-corrosion treatment, which is quite possible to perform in a garage.
Self-protection of thresholds requires not only desire, but also an understanding of technology, since simple painting will not help here. The main goal is to create a sealed, elastic layer that will block the access of oxygen and water to the metal. In this article we will look at how to treat thresholds, what tools are needed and how to avoid mistakes that turn the procedure into a waste of time.
Hidden sill cavities are an ideal environment for rust to develop if they are not treated properly. A mistake is to apply a protective compound only to the outer part of the threshold, ignoring the internal structure. Without access to air and light, rust develops there even faster than outside, and it can only be stopped by preventive measures. Next, we will consider in detail the choice of materials and stages of work.
⚠️ Attention: If there is already through corrosion on the thresholds, simple treatment will not help. In this case, welding and replacement of part of the metal is required before applying the anticorrosive agent.
Choice of materials: the better to process hidden cavities
The automotive chemicals market offers many solutions, but not all of them are suitable for treating internal cavities. Bitumen mastics, often used for the underbody, are too thick and will not penetrate the narrow cracks of the sills, leaving the metal unprotected. Internal parts require highly penetrating compounds that flow through the metal and displace moisture.
One of the most effective solutions is considered oil anticorrosion agents based on corrosion inhibitors. They remain liquid for a long time, filling all microcracks. Also popular wax compositions, which after drying form an elastic film. The main advantage of such materials is the ability to “self-heal” in case of minor damage.
To enhance the effect, two-component systems are often used. First, the cavity is treated with a rust converter (if there are pockets), then a primer is applied, and only then the main protective layer is applied. Cannon fat is also a time-tested remedy, although it requires warming up before use.
Necessary tools and preparation of the work area
High-quality processing is impossible without the right equipment. You will need not only the anticorrosive agent itself, but also the means for applying it. The main tool is a special gun with a long nozzle, which allows you to deliver the composition deep into the threshold. You will also need:
- 🛠️ Drill with a drill (usually 6-8 mm) for creating technological holes.
- 💨 Compressor for supplying air and blowing cavities.
- 🔦 A powerful flashlight or endoscope for visual control of processing quality.
- 🧴 Degreaser and rags for preparing surfaces.
Preparing your vehicle is a critical step. The car must be washed thoroughly, paying special attention to the wheel arches and the bottom of the doors. Thresholds must be freed from dirt, sand and peeling paint. If you neglect this stage, the anticorrosive will lie on the dirt and quickly peel off, sealing the moisture underneath.
Access to internal cavities often requires removing plastic covers or drilling holes in inconspicuous places. Technological holes usually done at the bottom of the threshold or under door hinges. It is important not to damage the amplifiers or any wiring that may be running inside.
Use a medical endoscope connected to your smartphone. This will allow you to see the condition of the metal inside the threshold and control how the anticorrosive layer is applied.
Anticorrosive application technology: step-by-step instructions
The processing process is divided into several stages, violation of the sequence of which reduces the effectiveness of protection. First, mechanical cleaning of accessible surfaces is performed. Then the metal is degreased. After this, you can begin applying the composition.
☑️ Checklist for preparation and application
The composition must be applied under pressure, starting from the point farthest from the hole and gradually moving towards the exit. It is important to cover the entire inner surface with an even layer. Overpressure may result in metal tearing or damage to factory welds, so keep an eye on the compressor readings.
After treating all cavities, it is necessary to give the material time to polymerize or absorb. This usually takes from several hours to a day, depending on the ambient temperature and the type of composition used. Only after complete drying can the technological holes be closed with rubber plugs.
⚠️ Attention: Do not apply anticorrosive to a hot body or in the sun. Rapid evaporation of solvents will lead to the formation of bubbles and a porous structure of the protective layer.
Processing of welds and hidden reinforcements
Welds are high-risk areas, as this is where corrosion often begins due to damage to the factory zinc coating. When processing thresholds yourself, these areas need to be given special attention. Sealing seams prevents moisture from entering metal joints.
To protect the seams, special seam sealants are used, which have high adhesion and elasticity. They do not crack due to body vibrations. Before applying sealant, the seam can be treated with an acid primer to neutralize possible rust.
Threshold amplifiers located inside also need protection. They are more difficult to reach, but the long spray nozzles allow you to cover these areas. If the amplifier is already affected by rust, it should be mechanically cleaned as much as possible and treated with a converter.
What to do if rust has already started from the inside?
If you see that the metal has become thinner, but there is still no hole, you can try the “injection” method. A rust converter is pumped into the cavity through a thin drill, converting the oxides into a stable compound. After drying, the cavity is filled with anticorrosive.
Comparison of popular threshold processing tools
The choice of a specific product depends on the budget, the condition of the car and the desired durability. There are products of both domestic and foreign production on the market. Below is a table to help you navigate the range.
| Product name | Base type | Service life | Features |
|---|---|---|---|
| Dinitrol 5500 | Oily | 2-3 years | High penetrating power, displaces water |
| Movil | Wax | 1-2 years | Cheap, readily available, requires frequent updates |
| Rust Stop | Oily | Up to 3 years | Hygroscopic, continues to work even in the presence of moisture |
| Cannon fat | Oil | 3-5 years | Traditional product, requires heating, very sticky |
When choosing, it is worth considering the climatic operating conditions. For regions with a humid climate and a large number of reagents, oil formulations are better suited. In dry climates, you can limit yourself to wax products.
Frequent mistakes when processing independently
Despite its apparent simplicity, beginners often make mistakes that reduce their efforts to zero. One of the most common is poor surface cleaning. Applying anticorrosive to dirt or loose rust will only preserve the problem.
Another mistake is using the wrong materials. As already mentioned, thick mastics for the bottom are not suitable for thresholds. They create a crust under which the metal continues to rot. It is also important not to forget to close all technological openings after processing, otherwise dust and water will get inside.
You should not skimp on the amount of material. Anticorrosive layer should be sufficient to completely cover the metal. A "dry" spray will not give the desired effect. It is better to spend more time on careful processing than to redo the work after a year.
The main secret of success is an integrated approach: high-quality cleaning, the correct choice of penetrating composition and regular monitoring of the condition of the thresholds.
Questions and answers (FAQ)
How often should threshold processing be repeated?
The recommended frequency depends on the material used and operating conditions. It is advisable to update oil anticorrosives once every 2-3 years, wax ones - annually. If the car is operated in harsh conditions (winter, reagents, off-road), it is better to inspect and touch up every autumn.
Is it possible to treat thresholds in winter?
Strongly not recommended. For high-quality adhesion and polymerization of most compositions, a positive temperature is required (usually above +10°C). In winter, the metal is cold, and the composition will not be able to spread and absorb properly.
Do I need to drill the sills if there are factory holes?
Factory holes are often not sufficient for quality processing, as they can be displaced or covered by amplifiers. Professionals will often drill additional holes in strategic locations to allow the sprayer to better reach all corners of the cavity.
Does the anticorrosion smell take a long time to dissipate?
Oil-based formulations may have a distinctive odor for several days after treatment until the solvents evaporate. Wax compounds smell less. If applied properly and the plugs are closed, there should be no persistent odor in the cabin.