The question of choice epoxy and acidic The ground stands before everyone who starts to restore the paint coating of the car. To make a mistake here means to condemn yourself to repainting in six months, when corrosion begins to creep under the paint. Many beginners confuse these compounds or, worse, try to replace one with another, without understanding the chemical nature of the processes.
Acid soil, often called phosphate or jettyIt is used for primary metal processing. Its task is not to create a thick film, but to enter into a chemical reaction with the surface, creating a microscopic layer that prevents oxidation. The epoxy composition, on the contrary, creates a powerful physical barrier, completely insulating the metal from oxygen and moisture. The choice depends on the state of the body and the stage of work.
In this article, we will discuss the technical nuances of both materials so that you can make an informed decision. We will not rely on the marketing slogans of manufacturers, but will consider the real effectiveness of formulations in an aggressive environment.
Chemical nature and principle of operation
The main difference lies in the protection mechanism. Acid soil It contains orthophosphoric acid, which literally "etches" the surface of the metal. The reaction produces insoluble phosphates that bind tightly to the base. This provides phenomenal adhesion, but the layer itself is porous and requires overlap.
epoxy It works differently. It is based on epoxy resins and hardeners. When mixing the components, polymerization begins, creating a monolithic film that is impermeable to water and air. Epoxy compounds do not react chemically with iron oxides, so they require a perfectly cleaned metal.
If you apply epoxide to rust or residues of an old coating, it will create a โgreenhouseโ under which corrosion will continue to develop with a vengeance. Acid is able to neutralize the smallest foci of oxidation, which cannot be removed mechanically. However, it does not give 100% waterproofing without finishing.
Can components of different soils be mixed?
Mixing hardeners and bases from different types of soils is strictly prohibited. The chemical composition of epoxy resins and acid solutions is incompatible. This will cause the material to not dry, soar or lose adhesion in a short time.
Applications: where and what to use
The choice of material is dictated by a specific section of the body and its condition. Phosphate soils They are indispensable when working with elements subject to high vibration and complex geometry, where it is difficult to achieve perfect cleaning. They are perfectly laid on welded seams and in hard-to-reach places.
Epoxy formulations are more often used to level surfaces before painting or to protect planes where perfect smoothness is important. They are perfectly polished and create an excellent base for putty (although some technologies recommend applying putty directly to the metal).
When repairing the bottom and arches, where the effect of moisture and reagents is maximum, a bundle is often used: first, an acidic to neutralize rust, then an epoxide for powerful insulation. However, it is important to observe technological pauses.
- ๐ Acid soil Ideal for: welded seams, hard-to-reach cavities, places with residual corrosion after cleaning.
- ๐ก๏ธ epoxy better for: flat surfaces of the body, creating an insulating layer for a putty (by 2K technology), protection from chips.
- โ ๏ธ Do not use acid under polyester putty without an intermediate layer, as the acid can disrupt the polymerization process of the resin.
Adhesion and durability of the coating
When it comes to metallic adhesion, jet-ground out of competition. The chemical bond they form is stronger than the mechanical bonding of epoxy resins. This is why they are used as the first contact with the body. However, the durability of protection is lower due to the porosity of the dried layer.
Epoxy coatings benefit in the long run due to their inertia. They do not allow electrolytes to pass through, which prevents the occurrence of electrochemical corrosion. When applied correctly to the prepared metal, such a coating serves for decades, without losing its properties.
โ ๏ธ Attention: Acid soil is hygroscopic. If left without overlapping with acrylic or epoxy soil-filler, it will begin to absorb moisture from the air, which will lead to the rapid appearance of new rust.
It is also important to consider compatibility with finishing. Most paints can be applied to epoxy soil, but only after full polymerization and easy grinding. The acid layer requires mandatory overlap, since the paint will fall on it poorly and may peel off.
Comparative Characteristics Table
For convenience of choice, the main parameters are summarized in a table. This will help you quickly navigate when buying materials in the store.
| Parameter | Acid (phosphate) | epoxy |
|---|---|---|
| Type of protection | Chemical (passivation) | Physical (barrier) |
| Rust application | Allowed (removes oxides) | Prohibited (pure metal only) |
| Thickness of layer | Thin (5-10 ฮผm) | Fat (up to 100 ฮผm or more) |
| Grinding | Not grinding (or very carefully) | Nice grinding. |
| Time to dry | 15.30 minutes. | 2 to 24 hours. |
As you can see from the table, materials solve different problems. Phosphation Epoxy is the construction of the main protective barrier. Trying to replace one with another is a technical mistake.
When working with two-component soils, always use scales for mixing. The proportions "to the eye" often lead to the fact that the soil either does not dry, or becomes too brittle (fragile).
Technology of application and surface preparation
The quality of the result depends on 80% of the preparation. For epoxy The surface should be cleaned to pure metal, defatted with antisilicone and dried. Any traces of oils or old paint will dramatically reduce adhesion.
Acid soil is less demanding to perfect purity, but degreasing is still necessary. It is usually applied with a thin layer of spray gun or brush (depending on the form of release). It is important to observe the temperature regime: most compositions work at a temperature not lower than + 15 ยฐ C.
โ๏ธ Body preparation algorithm
When applying epoxy, it is important to observe the interlayer drying time. If the second layer is applied too early, the solvents may remain inside, causing the bubbling. If you overhold the surface of the beyond time window (beyond the overlap window), you will need grinding to open the pores.
โ ๏ธ Warning: Epoxy soils are toxic when applied. Work only in a respirator with a carbon filter and in a well-ventilated room. Isocyanate vapors can cause severe allergic reactions.
Frequent mistakes in selection and application
One of the most common mistakes is the application of polyester It's right on the fresh acid soil. The acid contained in the soil can react with the components of the putty, disrupting the process of its curing. As a result, the putty may remain sticky or peel off along with the paint.
Another mistake is trying to save and use epoxy soil on poorly cleaned rust. Visually, the surface may appear flat, but under the epoxy layer, the oxidation process will continue. After a year, you will see bloating paint, under which there will be loose rust.
- โ Trying to grind the acid soil to zero - you erase the entire protective layer.
- โ Applying epoxy soil to wet metal - water will be baked under the film.
- โ Ignoring the life time of the mixture - diluted epoxy is suitable for 30 minutes to 2 hours.
Also, do not forget about the compatibility of materials from different manufacturers. Although the chemistry is similar, adhesiveness They may be different. It is better to use products of one line or proven ligaments.
The golden rule of the bodybuilder: Acid soil - to combat the remnants of rust, Epoxy - to isolate pure metal from the medium.
Final verdict: which is better?
The answer to the question โwhat is betterโ depends on your goal. If you need to save an element with focal corrosion that cannot be cleaned completely mechanically, choose the right one. acidic. He's mothballing the problem. If you make a quality repair with a complete removal of the coating to metal - your choice epoxy.
A professional approach often involves using both materials in a bundle. First, the metal is etched with acid for maximum adhesion, then covered with epoxide for waterproofing, and only then the filler and paint are applied. This sandwich structure provides the maximum life of the coating.
Do not skimp on preparation materials. The cost of a can of soil is negligible compared to the cost of repainting the part in a year. Quality 2K epoxy soil or proven Vixen or Body The acid will be a reliable basis for your project.
Can I apply paint directly to the epoxy soil?
Technically possible, if it is a base paint (metallic / pearl) and the soil is polished. However, epoxy soil often has a smooth surface, and a thin layer of primer-surfacer acrylic soil may be required to spread the base perfectly.
How much does the epoxy soil dry before grinding?
The drying time depends on the temperature and brand of the product. Usually, primary drying takes 2-4 hours at +20ยฐC. Full polymerization for grinding can take up to 12-24 hours. Some modern fast-drying compounds allow you to grind in 40-60 minutes.
How to dilute epoxy soil?
Only special diluents for epoxy soils (usually labeled as 2K Epoxy Thinner). The use of acetone or solvent 646 may lead to clotting of the resin or loss of adhesion.
Do I need to polish the acid soil?
Acid soil, as a rule, is not polished, since its layer is very thin (about 1 ฮผm). Grinding can disrupt the integrity of the protective film. If you want alignment, over the acidic apply acrylic filler, which is already grinded.