Restoring the appearance of the hull or completely repainting the vessel is not just an aesthetic procedure, but an important part of maintenance, extending the life of the product. Owners often wonder what fiberglass boats in factories and specialized workshops paint to get a coating that is resistant to aggressive marine environment and ultraviolet. Choosing the wrong composition can lead to peeling of the coating, bloating and, as a result, expensive repairs. polymeric.
The modern market offers a wide range of paints, but not all of them are suitable for fiberglass. The chemical structure of the binder in the paint must be compatible with the material of the body, otherwise the adhesion will be weak. In this article, we will discuss in detail the types of paints, their features, and the application technology that guarantees a long-lasting result.
Requirements for paint materials for fiberglass
Fiberglass, or fiberglass and polymer resin composite material, has unique properties that dictate harsh coating conditions: paint must not only protect the body from water and salts, but also withstand constant temperature changes, mechanical shocks on the berth and exposure to sunlight. If the paint layer is too rigid, it will crack when the body is microdeformed, and too soft will quickly wear off.
The key factor is adhesion The material's ability to bond firmly to a smooth or polished fiberglass surface. Many alkyd enamels popular in household construction simply won't stick to prepared fiberglass without special soil, and the coating must have high elasticity to compensate for the thermal expansion of the materials.
Before buying paint, be sure to check the compatibility of the solvent in the composition with the housing material - aggressive solvents can dissolve the upper layer of the old helcoat.
It is also worth considering that some paints require strict compliance with the temperature regime when applied. For example, two-component formulations may not polymerize at low temperatures, and at high temperatures they may catch too quickly, forming defects.
Epoxy paints: strength and chemical resistance
One of the most popular answers to the question of what fiberglass boats are painted by professionals is epoxy, two-component systems consisting of a base and a hardener that, when mixed, react irreversibly chemically, resulting in an incredibly hard, chemically resistant coating that is often used to paint the underwater hull (anti-fowling) or bottom.
The main advantage of epoxy paints is their exceptional adhesion and water resistance, which creates an impenetrable barrier to moisture, preventing osmosis, the process of water entering fiberglass through micropores, but they also have disadvantages: they can turn yellow under ultraviolet light, if not coated with varnish on top, and require careful surface preparation.
Why does epoxy turn yellow?
The phenolic groups in the structure of the epoxy resin are oxidized by UV rays, a purely cosmetic defect that does not affect the protective properties, but the board often uses polyurethane varnish on top of the epoxy soil.
When working with epoxy materials, it is important to observe the proportions of mixing components. The slightest deviation from the manufacturer's instructions can lead to the paint remaining sticky forever or, conversely, becoming too brittle.
Polyurethane enamel: glossy finish and protection from UV
If you want to have a mirror shine that's comparable to a car, polyurethane (2K polyurethane) paints are the best choice, and they're the ones that paint the surface of premium yachts and boats the most, and they're highly elastic, they're very color-resistant, and they don't burn out in the sun for decades. Polyurethane It creates a very strong film that is resistant to scratches and abrasion.
Unlike epoxy compounds, polyurethanes are more forgiving to application conditions, although they require indoor cleanliness. They come in a huge range of colors, including metallic and mother of mother of mother-of-pearl. An important feature is that polyurethane paint often requires application to a special epoxy soil for maximum adhesion to fiberglass.
- 🎨 Appearance: High gloss, deep color, lack of effect of "orange peel" when applied correctly.
- 🛡️ Defense: Excellent resistance to ultraviolet, salt water and gasoline.
- ⏳ Lifetime: After mixing the components, the mixture retains viability for 2 to 6 hours depending on the temperature.
It is worth noting that polyurethane paints are toxic when applied and require the use of a respirator with carbon filters. The vapors of isocyanates in hardeners can cause severe allergic reactions and asthma, so painting should be done in a well-ventilated room or outdoors using PPE.
Gelcouts: factory recovery technology
Helcoat is not really paint in the traditional sense, but a special layer of polyester or epoxy resin, rich in pigment, which is applied first in the form in the production of a boat. However, there are repair gelcoats that can repair damaged areas or even repaint small boats whole. the only material that, when cured, becomes a chemical part of the bodyIt creates a monolithic structure.
Using gelcoat to completely repaint is a time-consuming process, requiring a spray spray to apply high pressure, often in several layers, and then grind and polish. Unlike paint, gelcoat does not dry by evaporating the solvent, but polymerizes, so that the layer can be thick enough to hide small surface defects.
| Parameter | gelcoat | Polyurethane paint | Epoxy paint |
|---|---|---|---|
| Basis | Polyester/Epoxy resin | Polyurethane resins | Epoxy resins |
| Thickness of layer | High (up to 0.5 mm or more) | Low (micrones) | Medium |
| Difficulty of application | High (requires skill) | Medium/High | Medium |
| Repairability | High (local repairs) | Difficult (transitions visible) | Medium |
The main advantage of gelcoat over paint is its repairability: scratching on gelcoat can be sanded and polished until it disappears, while scratching on a thin layer of paint will require repainting the entire detail. However, for large areas, gelcoat can be too expensive and difficult to use for a beginner.
Acrylic and alkyd compositions: budget option
For small boats that are not operated in extreme conditions, or for temporary restoration of appearance, you can use acrylic and alkyd paints. They are much cheaper than professional yacht materials and easier to apply - often do not require complex equipment, brush or roller. Alkyd enamel create a sufficiently strong film, but inferior to polyurethanes in shine and durability.
Water-based acrylic paints are becoming increasingly popular due to their environmental friendliness and lack of a pungent odor, they dry quickly and allow the tool to be easily washed with water, but their adhesion to fiberglass without quality soil leaves much to be desired, and their resistance to constant immersion in water is limited.
☑️ Choosing budget paint
If you choose a budget option, be prepared to repaint the boat more often - every 2-3 seasons. In addition, such paints are less resistant to impact and can be chipped when in contact with hard objects. They are suitable for boats stored under the tent or indoors.
Technology of surface preparation and application
The quality of the painting depends on the surface preparation, 80%. Fiberglass often has a layer of wax (paraffin) on the surface, which protrudes to cure the resin in air, this layer must be completely removed, otherwise no paint will hold. acetone Or specialized washing of silicone.
The next step is machining, and a smooth gelcoat or old paint needs to be wrapped, and this uses sandpaper with grains from P240 to P400, and the goal is to create a uniform risk that will increase the area of the clutch, and the dust after grinding must be removed completely, best with compressed air and a sticky napkin.
⚠️ Warning: Never use chlorine-based solvents (e.g. dichloroethane) to degrease fiberglass. They can react with polyester resin, causing softening and bloating of the upper layer of the body, which will lead to irreversible damage.
After preparation, the soil is applied. The soil equalizes the absorbency of the surface and provides a chemical bond between the fiberglass and the finish paint. After drying the soil (observe interlayer exposure time!), paint is applied. Usually 2-3 thin layers are required to avoid undercurrents. Each layer must be sanded with a fine skin (P600-P800) before applying the next one.
The quality of surface preparation is more important than the brand of paint – on poorly prepared fiberglass, even the most expensive yacht enamel will begin to peel off after the season.
Common mistakes in painting boats
One of the most common mistakes is ignoring humidity and air temperature, painting in wet weather or high humidity causes moisture to condense into the paint layer, causing gloss to cloud, craters and bubbles, and optimal humidity for working with polyurethanes is no more than 70-75%.
Also, beginners often neglect the life of the mixture. Two-component paints begin to thicken after mixing. If you try to paint "at the end" of the life of the mixture, the coating will lie unevenly, with pitching, and will not spread. Always mix as much paint as you can produce in 30-40 minutes.
Another problem is that the layer is not thick enough, because too thin a layer of paint will not hide the risk of sandpaper and will look matte, even if the paint is glossy. On the other hand, too thick a layer will lead to the formation of "orange peel" and undertrenchments.
Can I paint a fiberglass boat with ordinary car paint?
Technically, you can use two-part car enamels (acrylic or polyurethane) with the right soil. Car paints give excellent gloss and durability. However, they can be less elastic than specialized yacht paints, and when the hull is severely deformed (wave impact) can crack. In addition, yacht paints are better protected from constant contact with salt water.
Do I need to remove the old gelcoat before painting?
You don't have to remove the old gelcoat completely if it's holding tight, you just have to remove all the flaked areas, splash the chips and carefully wrap the entire surface to a uniform matte state, and if the old gelcoat has deep cracks or osmosis blisters, then more serious repairs are required until the damaged parts of the fiberglass are replaced.
How much paint does the boat dry before launching?
The time of full polymerization depends on the type of paint. Epoxy compounds can dry from 7 to 14 days to full strength, although they stop sticking after a day. Polyurethane enamels are usually ready for operation after 7 days. The exact time is always specified in the technical data sheet (TDS) of a particular product. Descent into the water prematurely can lead to clouding and softening of the coating.