Possession dural-boat Aluminum alloys, such as duraluminum, are highly durable, but when exposed to water, especially salt water, they are subject to corrosion and fouling. The question of how to paint a dural boat is a challenge for any owner who wants to extend the life of their vessel. The wrong choice of material can lead to coating detachment and accelerated metal destruction.
The main difficulty lies in the chemical activity. aluminum. It immediately forms an oxide film on its surface, which prevents most paintwork from adhesing, and if you just apply regular enamel, it will quickly bubble and chunks will come off, which is why the technology of painting dural boats is so different from the processing of steel or wooden structures, and requires a specific approach to surface preparation and soil selection.
In this article, we will look at all the nuances of the process, from the paint selection type to finish polishing, you will learn which formulations provide maximum protection and which are better to bypass. Properly selected coating will not only improve the appearance, but also become a reliable barrier against aggressive aquatic environment.
Features of duraluminium corrosion and coating requirements
Duraluminum is an aluminum-based alloy with copper, magnesium and manganese, which is what makes the metal strong, but also makes it vulnerable to electrochemical corrosion. In water, the various components of the alloy form microvoltaic pairs, which leads to a spot breakdown of the structure. Corrosion It can develop under a layer of paint if it does not have sufficient insulating ability.
Dural boat coatings have two main functions: to create an insurmountable barrier to moisture and oxygen, and to provide a strong grip on metal. Conventional oil paints are not suitable here, because they do not have the necessary elasticity and chemical resistance, when hitting a pier or branch, such a coating trnet, and water will reach the metal.
⚠️ Attention: The use of paints based on lead meadows or copper-containing antifouling compounds (without insulating layer) on aluminum alloys is strictly prohibited! This causes a powerful electrochemical reaction that destroys the body in one season.
The important parameter is the elasticity of the dried film. Dural boats are often subject to vibration and deformation when hitting a wave. If the paint is too rigid, it will be covered with a network of microcracks. Through these cracks, moisture will penetrate the metal, causing the underfilm corrosion. polymerization The material should allow it to stretch along with the metal.
Overview of paint types for aluminum housings
The paint market offers several solutions that have proven themselves in non-ferrous metals, depending on the boat's operating conditions, budget and your skills in painting.
The most popular option remains epoxyThey create an extremely strong, chemically resistant coating that is perfectly maintained on properly prepared aluminum. Epoxy compounds are often used as soil-enamel, providing double protection. However, they are sensitive to ultraviolet light and require the application of the finish layer or the use of modified versions.
The second common type is alkyd-urethane They are highly glossy and resistant to fading, and polyurethanes are more elastic than epoxides, making them ideal for mechanically exposed upper layers. Alkyd paints (PF type) can be used, but their service life on water is much shorter, and they require more frequent renewal.
- 🎨 Epoxy enamel soils: Two-component systems with the highest adgzia, but requiring precise compliance with mixing proportions.
- 🛡️ Polyurethane enamel: Excellent resistance to ultraviolet light and mechanical damage, often used for finishing.
- 🧪 Alkyd formulations: Budget option for temporary protection or interior spaces, less durable outdoors.
And zinc is a zinc-containing soil, which works like a protector, but it's a very careful application to aluminum, and it has a more negative potential than aluminum, and can corrosion in some conditions. for dural boats it is safer to use special soils based on chromates or zinc phosphates, adapted specifically for light alloys.
Surface Preparation Technology: The Key to Success
Even the most expensive paint won't stick to dirty or smooth metal, and it takes up to 80 percent of the time to prepare, and it's a critical step, and the first thing to do is remove the old coating if it's damaged or flaked, and you can use chemical washes or mechanical methods to do that.
Mechanical cleaning is preferable because it allows you to immediately identify defects in the metal. Use abrasive grain grinders P80-P120 for rough sweeping and P180-P240 for finishing. Your job is to create risks that will catch the ground. Smooth, polished aluminum is a poor basis for painting.
☑️ Checklist for hull preparation
After cleaning, the surface must be thoroughly degreased. White Spirit, acetone It's important to wipe the surface with pure rags, changing it often so that you don't smear the fat around the body, and any stain of oil will be the center of the detachment of the paint in the future.
If there are dents or deep scratches on the body, they need to be put in a slipper. Only epoxy putty is suitable for aluminum. Polyester putty can hold poorly or cause corrosion due to the styrene content. Once dry, the putty is also grinded to level with the base metal.
Grounding: Creating an adhesive layer
The ground is the link between the metal and the finishing paint. grass-grass They contain acids that micro-graze the surface of the oxide film, providing chemical bonding, and you have to apply them in a thin layer, because they're very active.
Epoxy insulating soil is often applied after the etching soil, creates a thick, impermeable film, levels out fine irregularities and prevents metal from contacting water. The number of layers depends on the condition of the housing, usually 2-3 layers with interlayer drying are recommended.
| Type of soil | Basis | Drying time (20°C) | Compatibility |
|---|---|---|---|
| VL-023 (or VL-05) | Polyvinylbutyral | 15-20 minutes | All types of enamel |
| GF-021 | glyphatelic | 24 hours. | Alkyd enamel |
| EP-0215 | epoxy | 12:24 hours. | Epoxy, polyurethane |
| Zinc-filled | Epoxy/Silicate | 1-2 hours | Only with compatible finishes |
It is important to observe interlayer exposure. If you apply the second layer of soil too early, the solvent from the bottom layer may remain trapped, which will lead to swelling. If you overhold the soil beyond the time specified in the instructions, you may need to light grinding to improve the adhesion of the next layer.
Do I need to clean every layer of soil?
Yes, interlayer grinding (usually with abrasive P240-P320) removes the dust that has settled on the surface and creates a micro-relief for better adhesion of the next layer.
Finishing application
Once the soil is fully dried and prepared, it is the finishing paint, which can be applied with a brush, roller or spray gun, and the paint works best by providing a smooth surface without stripes, but requires skill and appropriate equipment.
In the case of two-component It is critically important to measure the components accurately, if you make a mistake in the proportions of the hardener, the paint will either not dry or become too brittle, and you need to mix the components carefully, but without intense stirring, so that the mixture does not saturate with air bubbles.
- 🌡️ Temperature: Paint should be at a temperature of +10 ° C to +25 ° C. Too low temperature will slow down polymerization, and high - will accelerate drying, which can cause defects.
- 💨 Humidity: Avoid painting in high humidity or fog, this can lead to clouding of the gloss (the “blushing” effect).
- 🧤 Defense: Work in a respirator and gloves. Solvent and isocyanate vapors (in polyurethanes) are toxic.
Apply the paint in 2-3 thin layers. The thick layer can flow or dry unevenly. Between the layers, be sure to keep the time specified by the manufacturer. After applying the last layer, the boat should be given time for full polymerization - usually 3 to 7 days before launching.
⚠️ Warning: Don't rush the boat into the water immediately after painting! It takes up to a week to fully polymerize many modern paints. Early contact with water can cause the film to swell and lose its protective properties.
Removal of defects and maintenance of coating
Even good painting can get damaged over time, and chipped stones or scratches from branches must be removed promptly to prevent corrosion under the coating, and local repairs must be done using the same materials that paint the boat, or special pencils.
Regular maintenance prolongs the life of the surface. After each navigation, it is advisable to wash the boat with fresh water, removing salt and dirt. Periodically, you can apply polishes for the boat hulls, which restore the gloss and create an additional hydrophobic layer.
Keep the boat under an awning or indoors. Ultraviolet is the main enemy of most paints, it causes grinding and fading of the surface, even if the film itself is intact.
If you notice bloating, you need to gently open it, clean it to metal, unplug it, and paint it, and ignoring the minor defects can cause you to have to repaint the entire board after a season. Prevention It is always cheaper and easier to repair.
The service life of a qualitatively applied coating on a dural boat is 5-7 years or more, but only subject to an annual inspection and timely elimination of minor damages.
Frequently Asked Questions (FAQ)
Can I paint a dural boat with a regular PF-115 enamel?
Technically possible, but not recommended for use on water, alkyd enamel (PF) have a weak adhesion to aluminum without special soils and quickly lose elasticity, this coating will last 1-2 seasons, after which it will crack and peel.
Do I need to remove the oxide film before painting?
Yes, natural oxide film must be removed mechanically (surfing) or chemically (grazing soil), and the oxide film itself does not provide a reliable adhesion to paint materials and can cause detachment.
How many layers of paint is optimally applied to the bottom?
Optimal scheme: 1 layer of etching soil, 2 layers of epoxy soil-insulator and 2 layers of finishing antifouling or wear-resistant enamel, total 4-5 layers of protective coating.
How to dilute thickened two-component paint?
Use only the solvent recommended by the manufacturer of the particular paint (as indicated in the technical data sheet). Usually xylene, solvent or special diluents (thinner). It is not recommended to add more than 5-10% of the solvent so as not to disturb the properties of the film.