Do-it-yourself painting of car sills: a complete guide from A to Z

Why thresholds require special attention and how to paint them correctly

Car thresholds are one of the most vulnerable parts of the body, constantly exposed to aggressive environmental influences. Sand, gravel, road chemicals, moisture and temperature changes gradually destroy the factory paintwork, leading to chipping, rust and corrosion. If measures are not taken in time, minor defects will turn into through holes requiring expensive repairs by welding. Painting thresholds with your own hands is not only a way to save money on a car service (the price of work in workshops starts from 8-15 thousand rubles), but also a guarantee of high-quality results if you follow proven technology.

Many car owners mistakenly believe that they can paint the sills “on the knee” with a spray can in an hour. In practice, this is a complex process involving surface preparation, anti-corrosion treatment, priming, painting and varnishing. Without the correct sequence of actions, the new paint will peel off within a few months. In this article we will look at step-by-step technology Taking into account the nuances for different types of thresholds (stamped, cast, plastic), we will tell you how to choose materials and tools, and also reveal the secrets of professionals that they use in car repair shops.

Before you start work, honestly assess your strengths. If the thresholds already have through corrosion or paint blisters of more than 30%, painting them yourself can only aggravate the problem. In such cases, it is better to contact a body shop. For everyone else, go ahead to the detailed instructions!

Tools and materials: what you need for work

The quality of painting depends 70% on correctly selected materials and tools. It’s not worth saving on them - cheap paint or primer will quickly lose its appearance, and low-quality abrasives will leave scratches on the metal. Here minimum set, which is required for work:

• 🔧 Grinder or a drill with a grinder attachment (power from 800 W) + a set of sanding wheels (grit P80–P1200)
• 🧴 Degreaser (for example, App Wash & Wipe or Body 700)
• 🎨 Primer (for metal - epoxy or acid, for plastic - adhesive)
• 🖌️ Paint (selection by car color code, two-component acrylic is better)
• ✨ Varnish (acrylic or polyurethane, with hardener)
• 🧽 Scotch Brite (gray and red) and masking tape 50 mm wide
• 🛠️ Spatulas (metal and rubber) + putty (for smoothing out dents)
• 💨 Compressor with a spray gun (or spray paint if your budget is limited)
• 🧤 Protective equipment: respirator, gloves, goggles

If you are painting thresholds for the first time, we recommend taking extra materials - especially primer and paint. Consumption depends on the number of layers and treatment area. For example, for a sedan Toyota Corolla (2015–2020) you will need about 300–400 ml of paint and 200 ml of varnish for both thresholds. For SUV type Nissan X-Trail consumption increases by 30–40%.

⚠️ Attention: Do not use a household vacuum cleaner to remove dust after sanding! Small particles of metal and paint can damage the vacuum cleaner motor. Only an industrial vacuum cleaner with a filter is suitable for these purposes. HEPA or a special blow gun.

Preparing thresholds: removing rust and old paint

This is the most time-consuming and responsible stage. 90% of unsuccessful paintings are associated precisely with poor surface preparation - rust residues or poorly removed old paint will lead to peeling of the new coating within 3-6 months. Let's start by dismantling all removable elements:

• 🚗 Remove the plastic sill covers (if any). On most models they are attached with clips and screws.
• 🔩 Unscrew the fender liner mounting bolts (if they interfere with access).
• 🧲 Remove magnetic moldings (if installed).

Next we start cleaning. Use a sander with an attachment P80 for removing rust and old paint. Work carefully so as not to rub the metal into holes! Pay special attention to:

• 🔍 Joints and bends of the threshold - moisture and rust accumulate here.
• 🕳️ Holes for drainage (if any).
• 🚗 The lower edge of the threshold - it most often suffers from sandblasting.

After rough sanding, proceed to sanding with sandpaper. P180–P240 to level the surface. Then degrease the threshold App Wash & Wipe or similar composition. If there are deep pits of corrosion left on the metal, they need to be filled with putty. To do this:

1. Apply a thin layer of putty with a rubber spatula.
2. Let dry for 15-20 minutes (depending on temperature).
3. Sand the putty with sandpaper P320–P400 to a perfectly flat surface.

Remove plastic trim and moldings|

Remove rust with a sander (P80)|

Degrease the surface with a special compound |

Fill deep sinks (if necessary)|

Sand the putty (P320–P400)|

Blow the thresholds with compressed air to remove dust -->

Priming: the secrets of strong adhesion of paint to metal

The primer performs two key functions: it protects the metal from corrosion and ensures adhesion (adhesion) of the paint to the surface. For thresholds it is better to use two-component epoxy primer — it creates a durable layer that is resistant to mechanical damage. An alternative is acidic soil (for example, Reoflex Acid Primer), which additionally passivates the metal, preventing rust.

Step-by-step priming instructions:

1. Applying the first layer. Dilute the primer with the hardener in the proportion indicated on the can (usually 4:1). Apply a thin layer with a spray gun with a pressure of 2–2.5 atm. Hold the gun 20–25 cm from the surface.
2. Drying. Let the soil dry for 10–15 minutes (at a temperature of +20°C). Don't blow dry - it may cause bubbles!
3. Sanding. Treat the surface with Scotch Brite P500–P600 to remove shagreen (irregularities).
4. Second layer. Apply the primer again, but more densely. After drying (30-40 minutes), repeat sanding with Scotch Brite. P800.

For plastic thresholds (for example, on Volkswagen Polo or Skoda Rapid) use special adhesive primer (primer). It improves the adhesion of paint to plastic. Apply it in 1 layer and dry for 20-30 minutes before painting.

⚠️ Attention: If after priming “craters” or bubbles appear on the surface, this means that the metal was not properly degreased or the humidity in the room is too high. In this case, you need to completely remove the soil and repeat the process.

Soil type	Application	Drying time (at +20°C)	Sanding
Epoxy	Metal thresholds, high anti-corrosion properties	4–6 hours	P500–P800
Acidic	Rusty areas, metal passivation	15–20 minutes	Can't be sanded
Adhesive	Plastic thresholds and moldings	30 minutes	P800–P1000
Acrylic	Final alignment before painting	1–2 hours	P1000–P1200

Painting thresholds: technology of applying paint and varnish

Now we move on to the most creative stage - painting. It is important to observe here three rules:

1. The room temperature should be +18–22°C (at a lower temperature the paint will take a long time to dry, at a higher temperature it will bubble).
2. Air humidity - no higher than 60%. At high humidity, a matte coating will appear on the paint (“orange peel effect”).
3. Paint and varnish should be applied in 2-3 thin layers, and not in one thick one. This will prevent leaks.

Step by step process:

1. Preparing the paint. Dilute the base paint with hardener and solvent in the proportion specified by the manufacturer (usually 2:1:0.5). For metallics and pearls, add 10–15% thinner for better spreadability.
2. Applying the base. The first layer should be translucent (“foggy”). Let it dry for 5-7 minutes. Apply the second layer more densely, but without smudges. For complex colors (eg. "Honda Civic" Red Pearl) a third coat may be required.
3. Drying the base. The time depends on the type of paint: acrylics dry in 20–30 minutes, metallics - up to 1 hour.
4. Varnishing. Apply varnish in 2 layers with intermediate drying for 10 minutes. Use quick drying hardener, if the temperature in the garage is below +18°C.

For spray painting, the technique is slightly different:

• 🎯 Keep the balloon at a distance 25–30 cm from the threshold.
• 🌀 Apply paint in circular movements, covering each new pass by 50%.
• ⏳ Pause between layers for 15-20 minutes.

Drying and polishing: final touches

After varnishing, the thresholds must dry at least 12–24 hours at room temperature. It is not recommended to speed up the process with a hairdryer or heater - this can cause microcracks in the varnish. If you painted in the garage in winter, use infrared heater at minimum power, placing it at a distance of 1.5–2 m from the machine.

After a day you can start polishing. It is needed to remove fine shagreen and add shine. Use:

• 🔴 Abrasive paste (for example, 3M 05999) to remove defects.
• 🟢 Polish without abrasive (for example, Sonax Nano Pro) for a final shine.
• 🛠️ Polishing machine with a soft circle (speed 1000–1500 rpm).

Polish the thresholds in a circular motion without pressing too hard on the machine. After polishing, apply wax protective composition (for example, Turtle Wax Ice) - it will extend the life of the paint and make it easier to maintain.

How to speed up paint drying without risk?

If you urgently need to use your car, you can use hot drying in a special chamber (temperature +60°C, time 2–3 hours). At home alternative - infrared lamp at a distance of 1 m from the threshold, but no closer! It is important to ensure that the varnish does not overheat (maximum +40°C on the surface).

Common mistakes and how to avoid them

Even experienced craftsmen sometimes make mistakes when painting thresholds. Here TOP-5 misses and ways to prevent them:

1. Poor surface preparation.

   If there are traces of rust or old paint on the threshold, the new enamel will quickly peel off. Solution: use rust converter (for example, Tsinkar) for hard-to-reach areas and sand the metal thoroughly.

2. Incorrect microclimate.

   High humidity or low temperature leads to a matte coating on the varnish. Solution: paint in a warm, ventilated area with humidity up to 60%. Use dehumidifier, if the garage is damp.

3. Thick layers of paint.

   They take a long time to dry and may bubble. Solution: Apply 2-3 thin layers with intermediate drying for 10-15 minutes.

4. Ignoring the primer.

   Without primer, paint does not adhere well to metal. Solution: Always use a primer, even if the sills “appear” clean.

5. Early exploitation.

   If you get into the car or close the doors before the varnish is completely dry, fingerprints will remain on the door sills. Solution: Do not touch painted surfaces for 24 hours.

If defects appear after painting, they can be eliminated:

• 🎨 Smudges: Carefully cut with a blade after drying and polish.
• 🌀 Shagreen: polish with abrasive paste P1500–P2000.
• 🟠 Matte spots: The cause is usually moisture. The problem area needs to be repainted.

FAQ: answers to frequently asked questions

Is it possible to paint the sills without removing them from the car?

Yes, but it will complicate the process. You will have to carefully cover the adjacent elements with masking tape and film so as not to splatter paint. For high-quality painting, it is better to remove the sills (if they are removable) or at least dismantle the plastic trims and fender liners.

How much does it cost to paint thresholds at a service?

The price depends on the region and complexity of the work:

• 🚗 Local painting (without removing thresholds): RUB 8,000–15,000.
• 🔧 Full painting with removal and anticorrosive: RUB 15,000–25,000.
• 🛠️ Repair of through corrosion (with welding): from RUB 20,000.

Self-painting will cost 3,000–6,000 rubles. (materials) + equipment rental (if you don’t have your own).

Which paint to choose: acrylic or metallic?

It depends on the color of your car:

• 🎨 Acrylic: Suitable for solid colors (black, white, red). Easier to apply, dries faster.
• ✨ Metallic/pearl: for “complex” colors (silver, metallic blue, pearl). Requires mandatory varnishing.

For rapids it is better to take two-component paint (with hardener) - it lasts longer.

How often should the paint on thresholds be renewed?

Service life depends on operating conditions:

• 🚗 Urban conditions (asphalt, washing 1-2 times a week): once every 3-4 years.
• 🏔️ Off-road, salt on the roads: once every 1-2 years.
• 🌧️ Humid climate (coastal regions): once every 2 years + additional anti-corrosion treatment.

Helps extend service life anti-gravel film or liquid glass (applied after polishing).

Is it possible to paint thresholds in winter in an unheated garage?

Technically possible, but the risks are high:

• ❄️ At temperatures below +10°C, the paint does not spread well, and smudges are possible.
• 💧 Condensation on metal worsens adhesion.
• ⏳ Drying time increases by 2-3 times.

Solution: use quick drying hardener and infrared heater, but make sure that the surface temperature does not exceed +40°C.