Threshold corrosion is one of the most painful problems for car owners, especially in harsh climates and reagents on the roads. When the owner notices a through hole, the question of “how to fix the holes in the thresholds” becomes critical, since ignoring the problem leads to further destruction of the power structure of the body. It is important to understand that the threshold is not just a decorative element, but an important part of the safety frame, and its integrity directly affects the rigidity of the body during a side impact.
There are many ways to solve this problem, from temporary measures using epoxy resins to capital reduction with the replacement of metal sections. The choice of a particular method depends on the degree of damage, the owner’s budget and the availability of specialized equipment. In this article, we will discuss in detail what materials are really effective, how to prepare the surface and why some popular “folk” methods can only make things worse in the long run.
Before taking action, a thorough defect must be made to understand the real scale of the disaster. Often the outer hole is just the tip of the iceberg, hiding extensive internal destruction. Deep corrosion It can spread under a layer of factory sealant, making the appearance deceptive.
Diagnostics of condition and assessment of the extent of damage
The first step in any repair is to objectively assess the condition of the metal. Visual inspection is often not enough, so experienced craftsmen use a magnet wrapped in a thin fabric to check the thickness of the paint coating and identify hidden foci of rust. If the magnet is not held or is held weakly where it should, then the metal is thinned or has already turned into iron oxide. It is also useful to gently knock problem areas: a ringing sound speaks of the whole metal, a deaf one - about the presence of a loose mass of rust or detached coating.
Particular attention should be paid to the inner cavity of the threshold. Through the technological holes or drilled with a diameter of 6-8 mm, you can run an endoscope or just a flashlight to assess the condition from the inside. Hidden corrosion It often develops faster than the external one due to condensation, which cannot evaporate. If the inside has turned into a sieve, then cosmetic finishing on the outside makes no sense - you will need a complete digestion or replacement of the element.
⚠️ If during the diagnosis it was found that corrosion affected the places of fastening of the racks or spars, the operation of the car becomes dangerous. In such cases, a professional bodybuilder is needed, since a violation of the geometry of the power elements can lead to unpredictable behavior of the machine in an emergency situation.
After the evaluation, a decision is made on the method of repair. If the damage is local and the metal has retained its strength, you can do the repair without welding. If the holes are through and there are many of them, and the metal around them is thin as paper, then the only correct solution is to create a new metal. cutting-off And welding the remix.
Materials selection: metals and repair kits
When the question of “what to fix the holes in the sills” is solved in favor of mechanical recovery, the key point is the choice of material for patching. The ideal option is to use the same type of steel from which the car body is made. It is usually low carbon steel with thicknesses of 0.8 to 1.2 mm. The use of too thin metal will lead to rapid burnout, and too thick - to difficulties with molding and welding.
There are ready-made repair kits on the market that include already stamped sections of the thresholds for popular car models. This makes the job much easier, as you don’t have to waste time on the flexibility and fitting of the geometry. However, for rare cars or unique cases of damage, it is often necessary to make patches manually from sheet metal. In this case, it is important to consider the direction of stamping in order to maintain the rigidity of the structure.
For temporary or budget repairs, fiberglass is sometimes used in combination with epoxy resins. This method allows you to close the hole without using a welding machine, which is important for those who do not have access to the equipment. However, such a “metal” does not have a load-bearing ability and serves only as a screen against dirt and water. epoxy composite It can crack with vibration over time, so you should not count on it as a permanent solution.
- 🔩 Sheet steel is a classic choice for welding, ensuring maximum strength and durability of the joint.
- 🧪 Repair fiberglass – suitable for sealing small holes in non-force zones, but requires careful surface preparation.
- 🛠️ Aluminum alloys are used less often due to the complexity of welding with conventional steel, but have high corrosion resistance.
When choosing a material, you should also pay attention to its anticorrosion resistance. Galvanized steel is preferred over black, as the zinc coating creates an additional barrier to rust. If conventional ferrous metal is used, the quality of subsequent corrosion treatment becomes a critical factor in longevity.
Why can't we use the foam?
Installation foam is hygroscopic, that is, absorbs moisture from the air. If you seal a hole in the threshold with foam, it will work like a sponge, holding water inside the structure. This will lead to accelerated rotting of the metal from the inside, and after a year or two the threshold will rot completely, and the process will be hidden from the eyes of the owner.
Welding technology: semi-automatic against gas welding
For high-quality threshold restoration, the most effective tool is the carbon dioxide semi-automatic (MIG / MAG). This method allows you to cook a thin metal (0.8 mm) without the risk of burning it, which often happens when using electrode welding. The essence of the process is to supply the wire to the welding zone in the protective gas environment, which prevents the oxidation of the molten metal. The seam is neat, durable and requires minimal post-treatment.
Gas welding (acetylene-oxygen) is also used, especially by experienced masters, as it allows you to visually control the temperature of the bath and cook "off-the-shoot", minimizing the thermal effect. However, gas welding requires a high level of skill and more complex equipment. For a beginner, the semi-automatic will be much safer and easier to master.
When welding a new insert, it is necessary to ensure good contact of the edges. The gap between the old and new part should not exceed 1-2 mm. If the gap is larger, the metal may simply fail or the seam will be leaky. Point welding The perimeter in increments of 15-20 mm is the optimal strategy for beginners, avoiding overheating.
⚠️ Warning: Before welding, be sure to remove the battery and turn off all electronic control units that are near the work area. Wandering currents can instantly disable expensive car electronics, and sparks can damage the interior or wiring.
After welding is completed, the seams must be cleaned with a petal circle or file to level the surface. Do not remove too much metal, it is enough to remove the influx for subsequent spatula. The quality of the seam directly affects how long the patch will stand and whether a crack will go along it.
☑️ Preparation for welding thresholds
Alternative methods: stainless welding
If the welding machine is not available or welder skills are not available, you can consider repair options without thermal exposure. One common method is the use of two-component epoxy compounds with reinforcement of fiberglass or metal mesh. This method is suitable for sealing small through corrosion holes, but does not restore the bearing capacity of the element.
The technology consists in thorough cleaning of the edges of the hole to pure metal, degreasing and applying the first layer of epoxy. Then a reinforcing material (glass fabric or small metal mesh) is applied, which is impregnated with the composition. There may be several layers, each of which should dry a little before applying the next. Cold welding In the form of bars or liquid compositions can also be used for sealing, but their adhesion to rusty metal is extremely low, so the surface preparation is critical here.
Another option is to install the pads. If the threshold has rotted from below along the entire length, sometimes it makes sense to cut the rotten area completely, and in its place weld or glue a new overlay on a powerful sealant. However, the sealant glue loses elasticity over time, and moisture can again begin to accumulate at the junction. Therefore, mechanical fixation (rivets or bolts) in combination with a sealant is often more reliable than just glue.
| Repair method | Strength | Durability | Difficulty of execution |
|---|---|---|---|
| Complete digestion (insert) | Tall. | 10 years. | Tall. |
| Partial lacquering | Medium | 3-5 years | Medium |
| Epoxide + fiberglass | Low. | 1-2 years | Low. |
| Cold welding | Low. | 6-12 months | Low. |
When choosing a weldless method, it is important to be aware that this is a temporary measure. Sooner or later, corrosion will continue its destructive effect under the sealant layer, if the cause of moisture inside the threshold is not eliminated.
Use copper anticor paste to treat the internal cavities of the sills before installing the plugs. It has excellent penetrating power and displaces water, creating reliable protection for years.
Anti-corrosion treatment and finishing
Repairing a hole is only half the battle. The main reason for the holes is corrosion, and if this process is not stopped, the new patch will rot as quickly as the old metal. The question of “what to do” is transformed into “what to protect”. After welding or patch installation, careful corrosion treatment must be carried out both outside and inside the threshold.
For the inner cavity, oily compositions-suppressors of water (type) are ideally suited Movile, Noxol or their equivalents. They penetrate the metal micropores, displace moisture residues and create an elastic film that does not crack when vibrating. Pouring the insides with thick bitumen mastics is not recommended, since they may not spread throughout the cavity and leave dry zones, and eventually dry out.
Outside, after spatula and painting, it is also useful to treat the joints and the lower part of the threshold with anti-gravel coating. It creates a strong armored layer that protects the LCP from the impact of stones and sand. Antigravium It is applied to a low-fat surface and dries long enough, so it is important to follow the technology specified by the manufacturer.
⚠️ Warning: Never paint over technological openings in the doorsteps tightly! They need to circulate air to remove condensation. If the holes are closed, a greenhouse effect is created inside the threshold, accelerating rot at times. Use special drainage plugs with valves.
Regular maintenance of anti-corrosion coating (every 2-3 years) will prolong the life of the repaired threshold for an indefinite period. Visual inspection of the state of protection will help to notice and eliminate minor defects before they develop into a big problem.
High-quality anticorrosion treatment is more important than the method of filling the hole itself. Without protection, any metal will rot, and with protection, even a thin patch will last for many years.
Frequent errors in the repair of thresholds
Many motorists, trying to save or speed up the process, make typical mistakes that negate all efforts. Understanding these errors will help avoid re-repairs in the near future. Often the problem lies not in the material, but in the violation of surface preparation technology.
One of the biggest mistakes is to put holes on top of the rust. Some simply cover the hole with a putty or epoxy without removing the oxidized metal. Rust is a hydroscopic material, it continues to “eat” metal from under the patch, expanding and tearing off the repair composition. Sweeping to shine A prerequisite for any repair.
Another common mistake is ignoring the inner cavity. After sealing the hole outside, the owner calms down, forgetting that the inside of the threshold continues to rot. Without anticory treatment, a new corrosion site will appear very soon. Also often used inappropriate materials, such as plaster mixtures or mounting foam, which are categorically not suitable for the body of the car.
- ❌ The absence of degreasing before applying the putty or paint leads to detachment of the coating.
- ❌ Using a too thick layer of putty - it cracks with vibration and gains moisture.
- ❌ Ignoring the temperature regime when painting - the paint may not dry or go bubbles.
Avoiding these mistakes and observing the technology, you will be able to qualitatively restore the thresholds of your car, returning it not only to presentable appearance, but also to structural integrity. Remember that the stingy pays twice, and quality repairs performed once will cost less than constant tinting and digestion.
Can I cook the rapids without removing the salon?
Theoretically possible, but highly discouraged. Sparks from welding can burn upholstery, carpet or seats. In addition, access to the lower part of the threshold from inside the cabin is often necessary for quality cleaning and processing. It is better to spend time on dismantling than to change the burned interior.
Can a hole in the door be sealed with cold welding?
Cold welding can temporarily seal a small hole so that the car reached the service or survived the winter. However, this is not a complete repair. Cold welding does not have the necessary strength and adhesion for long-term operation, especially in the zone of constant vibration and exposure to reagents. After a while, it will begin to peel off, and corrosion will continue.
Do I need to remove the doorsteps completely for repairs?
In most cases, the thresholds can be repaired on the car without removing them. Replacing the threshold completely sometimes requires dismantling if access to internal connections is limited. However, for local repair of holes, it is enough to provide access to the damaged area, removing the necessary elements of the body or cabin.
How often should I update the anticorer in the thresholds?
The recommended frequency of inspection and updating of anticorrosion coating is once every 2-3 years. In conditions of aggressive operation (permanent off-road trips, sea coast, use of reagents), the interval should be reduced to 1-2 years. Regular inspection will allow timely detection of violations of the protective layer.
Which is better: boiling together or overwhelming?
For sills, welding is preferable with a joint using a pad plate or a careful fit of the edges. Welding on top creates a pocket where moisture and dirt will accumulate, which will lead to accelerated corrosion at the joint site. If you cook it on top, be sure to boil the seam with a sealant.