In the process of body repair, painting or even when performing household tasks to remove old paint coatings, the master often faces the question of choosing a suitable chemical reagent.
This is especially true when choosing between two popular brands. solvent 646 and solvent 647Both products are widely marketed and have similar names.
Inexperienced users often confuse these liquids, considering them to be absolute analogues, but the difference in chemical composition dictates completely different use scenarios and effectiveness in specific conditions.
Chemical composition and basic characteristics
To understand which of the products has the greatest "strength" or aggressiveness, it is necessary to analyze their component composition in detail, since it is the percentage of substances that determines the physicochemical properties of the liquid.
Solvent 646 It is a complex mixture of eight organic components, among which acetone, toluene and butyl acetate dominate, which provides it with high evaporability and excellent solubility relative to most film forming agents.
Unlike him, solvent 647 It also consists of a mixture of organic substances, but the proportions here are shifted towards increasing the content of toluene and ethyl acetate, as well as adding butyl alcohol, which makes it more "soft" in the effect on some types of resins, but effective for other tasks.
Both products belong to the class of volatile liquids, however, the rate of their evaporation and temperature boiling modes of fractions can vary significantly, which directly affects the drying time of the paint layer.
⚠️ Attention: Both formulations are flammable liquids with a sharp toxic odor, so you can work with them only in well-ventilated rooms or outdoors, using personal respiratory protection.
The key difference is that 646 has more aggressive ketones in high concentrations, making it a more powerful tool for dissolving dried films.
Comparison of dissolving capacity
When it comes to the “power” of a solvent, it is usually implied that it can quickly and efficiently soften or completely dissolve dried varnishes, paints, enamels and bitumen stains.
In this context, solvent 646 is clearly considered to be more powerful and aggressive. The composition is compared to the 647th, so it copes better with old nitrocellulose and acrylic coatings.
The 647 brand fluid acts more delicately, which can be both an advantage and a disadvantage: it evaporates more slowly, allowing the paint to flow smoother, but worse takes heavily hardened contaminants.
If your goal is to quickly wash off old paint or degrease the surface before applying a resistant coating, the 646 will show itself as a more powerful fighter.
- 🧪 646 destroys the molecular bonds in the dried enamel faster.
- 💧 The 647 provides smoother dissolution without a sharp change in viscosity.
- 🌡️ The 646 has a higher evaporation rate, which speeds up the drying process.
- 🛡️ 647 less often causes clouding of the lacquer layer on sensitive surfaces.
It is important to note that the high aggressiveness of the 646 requires caution when dealing with certain types of plastic, as it can cause them to deform or dissolve.
Before using any solvent on a visible part of the car, be sure to test on an inconspicuous area to make sure there is no negative reaction of the material.
Applications in auto repair
In the field of automotive body repair, the choice between these two liquids often depends on the stage of work performed and the type of paintwork used.
Solvent 646 It is traditionally used to dilute nitro-emals, nitrolacs, epoxy resins and some types of acrylic paints, as well as to thoroughly wash the tool after work.
It is used when it is necessary to achieve high adhesion and rapid drying, for example, in the preparation of metal surfaces or the removal of bitumen spots from the body.
Solvent 647 more often finds application for dilution of alkyd enamels, melaminoalkyd varnishes and paints, where a longer drying time is required to form a smooth surface without defects.
| Characteristics | Solvent 646 | Solvent 647 |
|---|---|---|
| Basis | Ketones, ethers, alcohols | Toluene, butyl acetate, alcohols |
| Aggressiveness | Tall. | Medium |
| Evaporation rate | Very high. | Tall. |
| Principal application | Nitroemali, cleaning. | Alkyd enamel, lacquer |
The 647 is also often recommended for making materials sensitive to too rapid drying to avoid the orange peel effect.
Can I mix 646 and 647?
Mixing these solvents is technically possible because they have a similar chemical basis, but is not recommended by professionals. The proportions of the components in the mixture will become unpredictable, which can lead to a change in the drying time of the paint, the appearance of matteness or defects on the surface. It is better to use the product recommended by the manufacturer of paintwork.
Effects on different types of surfaces
The choice between 646 and 647 is critical when dealing with heterogeneous materials, as their effects on plastic, rubber and metal can be drastically different.
Plastic body elements such as bumpers, moldings and spoilers can be affected by contact with 646 solvents, which can cause softening, bloating or even dissolution of certain types of plastics.
In this regard, the 647 looks like a safer option for delicate surfaces, although it should not be poured on plastic unnecessarily.
Metal surfaces both compositions tolerate well, but after using 646th it is recommended to start applying soil or paint faster, as it actively removes any protective fat films and can contribute to the rapid oxidation ("rusting") of pure metal in air.
⚠️ Attention: If 646th solvent hits rubber seals or hoses, they may swell and lose elasticity, so avoid prolonged contact of aggressive chemicals with rubber products.
Painting also reacts differently: 646 can cause varnish clouding ("whitening") if the application technology is broken or the wrong ratio of components is selected.
Safety and storage conditions
Working with both types of solvents requires strict compliance with safety rules, since the vapors of these substances are toxic and at a certain concentration form explosive mixtures with air.
Store containers must be in a tightly closed container, away from open fire sources, heating devices and direct sunlight, at a temperature not higher than +35 degrees Celsius.
In the room where these liquids are stored or used, effective ventilation must be provided, and the concentration of vapours in the air must not exceed the maximum permissible values.
- 👓 Be sure to use safety glasses to prevent splashes from getting into the eyes.
- 🧤 Work in chemical-resistant gloves (nitrile or neoprene).
- 🏭 Ensure a constant flow of fresh air into the work area.
- 🚭 It is strictly forbidden to smoke or use open fire near open containers.
In case of fluid on the skin, you must immediately wash the affected area with a large amount of water with soap, and if you get into the eyes, thoroughly rinse with water and consult a doctor.
☑️ Safe work rules
The final choice: what is better to buy?
The answer to the question “what is stronger” is clear: solvent 646 It has higher chemical activity and dissolving power.
However, the concept of “better” depends solely on your specific tasks: if you need to wash the tool from dried paint or degrease the metal for painting – take 646th.
If your goal is to dilute the paint to produce the perfect gloss without leaks and turbidity, especially in unheated garage conditions or when working with sensitive enamels, then the 647 may be a better choice.
Do not chase for maximum "strength" where moderation is needed, as excessive aggressiveness can spoil the result of expensive repairs.
The strength of solvent 646 is higher, but for dilution of paints, it is often not power that is more important than the rate of evaporation and compatibility with a particular type of enamel.
When buying, always pay attention to the GOST or TU indicated on the label, since the quality of products from different manufacturers can vary significantly even within the same brand.
Can solvent 646 be used instead of 647?
In most cases, replacement is possible, but with caution. Because the 646 is more aggressive and dries faster, it can cause the varnish to cloud or the paint to dry too quickly, leading to defects. For nitro-emals, replacement is permissible, for alkyd ones - undesirable.
Which solvent is better at removing bitumen from the body?
For the removal of bitumen spots is better suited more aggressive solvent 646 Or specialized bitumen cleaners. It softens the complex hydrocarbon compounds contained in the road tar faster.
Why did the solvent cause divorces?
Dilutions may occur due to too rapid evaporation of the solvent (especially 646th), which leads to condensation of moisture from the air on the cooled surface, or due to incompatibility of the chemical composition of the solvent with the type of varnish.
Is there a difference in price between 646 and 647?
The difference in price is usually minimal and depends more on the manufacturer and volume of the container than on the brand of the solvent. However, the 646 is often a little cheaper because of the mass production and lower content of expensive alcohols.