The appearance of characteristic traces of corrosion, which people aptly called planeboatThis defect not only spoils the aesthetic appearance of your boat, but also signals the beginning of destructive electrochemical processes. If you do not stop the spread of oxides in time, a thin layer of metal can turn into debris, leading to serious leaks and expensive repairs.
Many newcomers mistakenly believe that aluminum alloys do not rust like steel and ignore the first signs of tarnishing. However, aluminum reacts actively with oxygen and salts in the water. The resulting whitish or gray crust is an oxide film that normally protects the metal, but when production or operation is disrupted, it begins to grow inwards, forming deep sores.
In this article, we will explain in detail why this problem arises, how to properly prepare the surface and what modern coatings will provide long-term protection for your vessel. Airboats are subject to aggressive environmental effects all year round, so knowledge of the nuances of anticorrosion treatment is necessary for every water motor.
The nature of corrosion on aluminum alloys
The main cause of the so-called scales is galvanic corrosion, which occurs when heterogeneous metals come into contact in an electrolyte, played by river water or sea water. Aluminum in the electrochemical series of stresses is left of many metals, making it an anode paired with copper, brass or even stainless steel. In the places of attachment of fittings, transom boards or engines, most often, and the centers of destruction.
The second critical factor is the quality of raw materials, and cheap models made from high-impurity technical aluminum oxidize much faster than aviation alloys, such as the one used in the production of aeroplane. AMG5 or AMG61Impurities create microvoltaic vapors inside the metal itself, triggering a process of point corrosion that looks like a scattering of small white dots gradually merging into a solid plaque.
⚠️ Warning: The use of steel bolts and nuts to assemble aluminum casings is strictly prohibited without reliable insulation. Contact of steel and aluminum in water accelerates corrosion by dozens of times.
It is also worth considering the impact of wandering currents, if the boat is often standing on water with the shore power connected or near the equipment working. Electrolytic destruction of the metal occurs rapidly and can lead to through holes in just one navigation season. planeboat It is not just dirt, but a symptom of deep chemical changes in the structure of the metal.
Diagnostics of the condition of the body and assessment of damage
Before you start taking active action to remove plaque, you need to carefully examine the body. The initial inspection is visual: look for paint bloating, whitish powder plaque and characteristic bumps. Often under the layer of old paint there are already ready-made corrosion centers, which, when tapped, emit a deaf sound that is different from the ringing of healthy metal.
For a more accurate diagnosis, you can use a special corrosion marker or a simple chemical test with a solution of copper sulfur, although the latter method requires caution not to damage healthy areas. If you find that the metal under the scales has become loose and layered, then the process has gone too far and requires not just a sweep, but a patch or a replacement sheet.
Pay special attention to the areas around the welds, and that's where the structure of the oxide film is most often broken and active oxidation begins. Argonne-arc welding minimizes risks, but if the seam is made with gas or with a violation of technology, planeboat It will appear along the welding roller first, and deep sores may not be visible from the outside, so try to feel suspicious places.
Mechanical cleaning and surface preparation
Well-designed surfaces are 80 percent effective in corrosion control, starting with a thorough freshwater wash, using specialized cleaning products that remove oil stains and biological fouling, and only after drying completely can the oxides be mechanically removed.
Use abrasive materials to remove the main layer of scales. P80-P120 sandpaper is suitable for removing the thick layer of oxides, and for finishing, switch to P240-P320. It is important not to overdo it or remove the excess thickness of the metal, especially on the bottom. In hard-to-reach places, corners and around rivets, it is convenient to use coral grinding discs or special brushes for drills.
☑️ Checklist for hull preparation
After mechanical cleaning, the surface must be degreased. Nefras C 50/170 (Kalosha) or specialized degreasers. Don't use acetone in large areas, as it can leave a vegetative and evaporates quickly before it can dissolve the fat film. The surface should be matte and completely clean, without any traces of dust or oil.
Chemical treatment and rust converters
Mechanical cleaning is often not enough to stop the chemical reaction completely, chemical rust converters that turn iron and aluminum oxides into stable compounds come to the rescue, and orthophosphoric acid formulations with zinc or chromates are suitable for aluminum, although the latter are becoming less popular due to toxicity.
The etching process removes microscopic oxide residues from metal pores where the sandpaper will not reach. After applying the composition and aging for the time specified in the instructions (usually 10-20 minutes), the surface is washed with plenty of water and neutralized with a weak alkaline solution, for example, a solution of soda ash.
RAVs and alcohols
| Type of instrument | Basis | Time of action | Features of application |
|---|---|---|---|
| acid transducer | Orthophosphoric acid | 15-30 minutes | It requires careful cleaning and neutralization. |
| zinc-containing soil | Epoxy resins + zinc | 24 hours. | Creates cathode protection, does not require flushing |
| Conversion coverage | Chromats/Circonates | 10-15 minutes | High toxicity, requires special protection |
| Neutral cleaner | 5 minutes | Only for mild contamination, does not poison |
Therefore, apply the grounding layer is necessary immediately after drying the neutralizing solution, without waiting for the appearance of a new film of oxides.
Selection of protective coating for bottom and sides
The choice of finishing depends on the operating conditions of your vessel. Aluminum boats are categorically not suitable paints containing copper (antifouling), as they will cause a powerful galvanic pair. The optimal choice is epoxy soils and polyurethane enamel, which create a strong, inert film.
Epoxy soils have excellent adhesion to aluminum and barrier properties, preventing oxygen and moisture from accessing the metal, but they are afraid of ultraviolet light, so they require the finishing layer to cover the reflective enamel. Polyurethane paintsThey are more elastic and resistant to impact, which is important for boats, often mooring to concrete walls or stones.
Can I use regular car paint?
Alkyd-based (glyphthal) car enamels have good coverability but less elasticity. For an aeroboat that experiences vibration loads and wave shocks, it is better to use two-component polyurethane compounds specifically for marine applications.
When applying paint, it is important to observe temperature and humidity. The optimal temperature for most marine paints is from +15 to +25 degrees Celsius. It is better to apply the material with a spray gun in two or three thin layers, allowing each layer to dry according to the manufacturer's instructions. The dry layer should be at least 60-80 microns thick for reliable protection.
Prevention and operation rules during the season
Even the best protection will not last forever without proper care. The main rule is not to leave the boat in the water for a long time unnecessarily. Aluminum breathes, and constant immersion reduces the life of the coating. After each foray into the water, especially at sea, the hull must be rinsed with fresh water to wash off the salt.
Regularly inspect the condition of zinc treads if they are installed on your boat. These small bars of active metal take the corrosion blow, sacrificing themselves to preserve the hull. If zinc has dissolved completely, it must be replaced, otherwise aluminum will react.
Keep the boat in an inverted position or under an awning with good ventilation. The accumulation of moisture under the awning without ventilation creates a greenhouse effect ideal for the development of corrosion.
If you find small chips or scratches, don't wait for the end of the season. Close the damage with any nitrogen or even regular nail polish as a temporary measure to stop the process. Scales on the aeroboat It develops exponentially: a small point in a month can turn into a through hole.
Anodic protection and additional measures
For boat owners with outboard motors and complex electrical equipment, the installation of cathode protection systems is important, and the principle of operation is simple: a source of current or a more active metal (tread) is connected to the hull, which becomes an anode in the galvanic pair, as a result (corrosion) is transferred to this sacrificial element.
The most common treads are made of zinc, magnesium or aluminum-zinc-indium alloys. The choice of material depends on the salinity of the water: magnesium works better in fresh water, zinc in salt water. Installing a tread on a transom or the cheekbones of a boat can significantly extend the life of the hull, especially if the boat is often standing on water with electricity.
⚠️ Attention: Incorrectly calculated cathode protection system can lead to "overprotection" when aluminum begins to release hydrogen and peel paint with alkali. Consult with specialists when selecting the area of treads.
Remember to check the electrical circuit between the motor and the boat. It's often the motor is protected and the boat is not, or vice versa. The galvanic interchange through special couplings helps to avoid leakage currents, which also contribute to the destruction of metal.
Seasonal storage and conservation
Preparing for winter is a critical stage for the longevity of your boat. Before storage, you need not only to wash the hull, but also to conduct an audit of all protective coatings. The damaged areas are cleaned and painted. The boat should be installed on special slipways or keel blocks, ensuring an even distribution of weight to avoid deformation of the hull during the winter.
The inside of the boat should also be perfectly clean. Remove all the residues of fish, oil and dirt. To preserve the metal parts, you can use special spray preservatives that create an oily film. It is better to keep the boat indoors or under a quality breathable case that protects from precipitation, but does not create condensation.
Proper preservation for the winter extends the life of the aluminum casing by 5-7 years, preventing the development of latent corrosion during the downtime.
In the spring, before you go down, do a check-up. Wash the conservatory, check the condition of the transom and bottom. Easy polishing and applying protective wax will help to update the appearance and create an additional barrier to water. Remember, regular care is cheaper than replacing the sheets of skin.
Frequently Asked Questions (FAQ)
Can I paint the scales on the aeroboat without cleaning?
It's not recommended. If you paint the oxides, the corrosion will continue under the paint layer. After a short time, the paint will rise and fall off with the new layer, and the hole will become even larger.
Which paint is best for aluminum?
The best-known two-part epoxy-polyurethane systems are those that provide a chemical bond to metal and high mechanical strength. Single-component alkyd paints hold worse and crack faster.
How often should zinc treads be changed?
The frequency of replacement depends on the intensity of operation and salinity of the water, and on average, a visual inspection is performed every month in the season, and if the tread has lost more than 50% of its original volume or has become covered with loose coating, it should be replaced.
Is white scales dangerous to the integrity of the boat?
The white oxide film itself (aluminum scales) even protects the metal from further oxidation if it is dense, is dangerous loose, gray or black corrosion that "eats" the metal deep, but to apply the paint quality, any scales must be removed.