Painting a car with a can: can you apply paint over the old coating

The desire to update the look of a car or hide minor defects often faces the harsh reality of a professional bodywork budget. Car owners are looking for alternatives, and the most affordable option seems to be aerosol can. However, the question of whether it is possible to paint the car with a spray over old paint without a complete clean-up to metal, is causing obese debate among motorists and professionals.

The short answer is: technically it is possible, but the result and durability of such a coating directly depend on the state of the current paint layer and the quality of preparation. adhesion (contact) is a key factor that cannot be ignored. If you apply a new layer on a glossy, greasy or damaged old, the paint will rise or peel off in a couple of months.

In this article, we will analyze in detail the technology of applying aerosol enamel to the existing coating, analyze the risks and provide a step-by-step algorithm of actions for those who decided to do this experiment. It is important to understand that even with perfect adherence to the technology, the resource of such painting will be less than that of a professional painter. chamber-colouring.

Analysis of the condition of the old paint coating

Before picking up a can, it is necessary to conduct a thorough diagnosis of the current condition of the body. You can not just spray new enamel on top of any coating. If the old paint layer has deep cracks resembling turtle shells, or detachments, applying the new material will only preserve the problem, which will soon manifest itself again.

Particular attention should be paid to places where repairs have already been carried out using putty. Over time, moisture can penetrate into these places, causing corrosion under the paint layer. Applying aerosol paint over rust without pre-treatment with a converter and soil will lead to rapid development of corrosion under a new layer in a matter of weeks. This is a critical point that many beginners miss.

Check the hardness of the old coating. If the varnish is easily scratched by the nail or has a sticky structure, this indicates a violation of the technology of previous painting or the use of low-quality materials. In this case, the new layer can react chemically with the solvents of the old one, causing the surface to wrinkle.

To assess the condition, use the following criteria:

• 🔍 Visual inspection in bright light for swelling and cracks.
• 🖐 Tactile check of smoothness and lack of stickiness.
• 💧 Water absorption test (if water is absorbed instantly, the varnish may be damaged).
• 🧲 Using a magnet to identify thick layers of putty.

⚠️ Attention: If the area of the damaged coating exceeds 30% of the area of the part, local spray painting has no economic and aesthetic sense. It is cheaper and more correct to remove the old cover completely.

Selection of materials and preparation of the workplace

The quality of the final result depends on the preparation and 50% on the materials used. The market offers a huge variety of aerosol paints, but not all are suitable for a car. Ordinary household enamel do not have the necessary elasticity and resistance to ultraviolet light, so through the season they can fade or crack.

You will need specialized automotive soil in an aerosol, which will provide adhesion to the old gloss, and high-quality varnish (if you paint in color "metallic" or "pearl"). Also degreasing, abrasive materials of different grains and paint scotch. You can not save on solvents - cheap compositions can eat the old layer of paint.

Preparation of the place also plays a role. Dust is the main enemy of aerosol painting. Even microscopic particles that have settled on wet paint will spoil the appearance. Ideal garage with pre-humidification of the floor to nail the dust, or specially equipped paint chamber.

List of necessary tools and materials:

• 🎨 Car paint in a can (selected by body code).
• 🛡 Acrylic two-component soil in an aerosol.
• 💨 Degreaser (antisilicone).
• 📏 Abrasives P800, P1500, P2000.
• 🧤 Respirator and gloves.

Technology of surface preparation for painting

The most time-consuming stage is matting. Paint with a spray over a glossy old varnish is categorically impossible - the new material just leaks or lies "coat". It is necessary to create a risk for which the soil or new enamel will catch. For this purpose, sandpaper or abrasive sponges are used.

Start by washing the part to remove dirt that can scratch the surface when grinding. Then carefully matt the entire surface you plan to paint, as well as the transition zone around it. Your task is to make the surface evenly matte, without gloss bald spots. Use water when grinding to clog less abrasive and wash away dust.

After matting, the degreasing stage follows. Rub the surface with a napkin dipped in antisiliconeAnd immediately wipe dry clean rags. Do not rub too hard so as not to smear the contamination. If there is fat from the fingers on the surface, the paint will not lie down in this place.

Next, it is necessary to protect the neighboring elements that are not subject to coloring. Use paint tape and cover film or newspapers. The edges of the tape should be tightly pressed so that the paint does not leak under them. Pay special attention to rubber seals and plastic parts.

Paint and varnish application process

The technique of applying paint from a spray can is radically different from working with a spray gun. Here the distance, speed and angle of inclination are important. The optimal distance from the nozzle to the surface is 15-20 cm. If you bring closer, the leaks can not be avoided; if further - the paint will dry in flight, lying dry dust.

The first layer is applied to the soil (if you do not use soil enamel). It dries quickly, usually 15-20 minutes. Then the first thin layer of paint is applied - "spilt". It's for the clutch. Don’t try to cover everything up the first time. It is better to make 3-4 thin layers with interlayer drying for 10-15 minutes than one thick one, which will go bubbles.

When working with the canister, constantly shake it. The ball inside should rattle. This ensures uniformity of color and consistency. If you paint metallic, the last layer can be made more foggy (sputter) to evenly stack the grain.

Spraying technique:
1. Start moving your hand beyond the detail.
2. Smoothly hold your hand along the surface.
3. Finish the movement outside the detail.
4. Don't stop at one point!

If varnish is used, it is applied after complete polymerization of the base (usually after 20-30 minutes). Lacquer is placed in 2 layers: the first thin, the second - more greasy, glossy. It is the varnish that will give depth of color and protection.

Secrets of the professionals

The temperature of the canister should be about 20 degrees. If it is cold, the pressure drops and the spray torch becomes narrow. If it is hot, the paint can boil in the balloon. Keep the cylinder in the room where the painting is carried out for at least 2 hours before the start of work.

Comparison of methods: spray spray

Many people doubt whether it is worth contacting the can if there is an opportunity to rent a compressor. Let’s compare these methods objectively so you understand the limitations of aerosol technology.

Parameter	Aerosol spray	Krascopult (compressor)
System pressure.	It constantly falls as you use it.	Stable, regulated
Quality of torch	Fixed, often uneven	Adjustable, uniform
Speed of operation	Low (low volume of paint)	Tall.
Cost of equipment	Minimum (price of cylinder)	High (apparatus + compressor)
The risk of shaking	High in case of violation of technology	Low when set up

As you can see from the table, the canister loses in pressure stability. When the balloon is empty by 30%, the pressure drops and the nature of the spray changes. This can cause the bottom of the part to be painted differently than the top. Professionals solve this by using multiple cylinders or special holders with heating, but at home it is difficult.

However, for local repair scratches on the bumper or wing canister is ideal. It allows you to make repairs quickly and cheaply without buying expensive equipment that may no longer be needed.

Polishing and finishing

After drying the paint (full polymerization takes from 24 hours to several weeks depending on the chemistry), the surface may have defects: shafts, dust, matteness. This is normal for aerosol painting. Fixes it with polish.

You can start polishing only when the varnish or enamel gain hardness. If you start polishing too early, the abrasive will simply "stripe" the fresh paint. Check the readiness with the nail: if there is no trace, you can try.

Use an abrasive paste and a soft-circle polishing machine. Movements should be smooth, without strong pressure. Your task is to remove a micron layer of varnish, removing the shaft and leveling the surface to a mirror shine.

⚠️ Attention: On the sharp edges of the body (fins of the wings, hood), the paint layer is always thinner. These places should be polished with extreme care or avoided so as not to wipe the coating to metal.

Frequently Asked Questions (FAQ)

Do I need to remove the old paint completely before painting with a spray?

No, complete removal is only required in the event of severe corrosion or detachment of the paint throughout the area. If the coating is held tight, enough matting (creating risks) to improve the adhesion of the new layer.

How much dried paint from the spray before polishing?

Externally, the paint can dry in 30-60 minutes, but polymerization and hardness set required for polishing, requires a minimum of 24 hours at a temperature of +20 ° C. In the cold season, the period increases to 2-3 days.

Can I paint with cans in winter on the street?

It's not recommended. Low temperature and high humidity will lead to clouding of the varnish (the effect of "bliness"), poor adhesion and long drying. The dust and snow will also ruin the job. You need to paint in a warm, dry room.

How to choose a color if the color code has faded?

If the car is old, the color code may not match the actual hue due to burnout. In this case, it is better to make a computer-based selection of paint at a specialized point, providing a sample (for example, a gas tank hatch or the interior of the door).