The Ultimate Guide To Finishing Your Aluminum Boat

Aluminum boats are lighter than fiberglass, making them easier to tow and launch. They are also more impact-resistant and generally require less maintenance. However, owners often seek to polish their aluminum boats to achieve a mirror-like finish. This process can be time-consuming and laborious, requiring several steps such as surface preparation, contaminant removal, and polishing. The type of products used and the techniques employed can impact the final result. While some opt for manual polishing, others suggest using power tools such as electric buffers or orbital sanders for efficiency. Proper maintenance of an aluminum boat's exterior and interior is essential to preserving its appearance and value.

Cleaning the exterior

The exterior of an aluminium boat should be cleaned and maintained regularly to preserve its appearance and protect its value. Here is a step-by-step guide to achieving a clean and polished exterior:

Materials and Tools:

• Freshwater
• XPS Aluminium Cleaner or a mild detergent
• XPS Wax and Sealant
• Wet rag
• Soft cloths
• Hose
• Clay bar (optional)
• Marine aluminium polish
• Polishing pad
• Sandpaper (grit ranging from 120 to 2000)
• Vegetable oil
• Red Tripoli
• Dual-action polisher
• Foam pads
• Microfibre pads

Step 1: Surface Preparation

Start by thoroughly cleaning the surface of your aluminium boat. Use freshwater to rinse the boat after each use, especially if it has been exposed to salt, polluted, or brackish water. Pay special attention to the hull waterline, as visible scum and dried algae can be challenging to remove if left for too long. Use a wet rag to wipe away any scum or residue immediately after hauling the boat out of the water.

Step 2: Contaminant Removal (Optional)

If there are tough contaminants like tar or tree sap on the exterior, you may need to use a clay bar designed for marine applications. This step will help lift and remove embedded contaminants without damaging the aluminium surface. Lubricate the surface, then gently glide the clay bar back and forth before rinsing the boat thoroughly.

Step 3: Polishing

To achieve a mirror-like shine on your aluminium boat, you will need to use a marine aluminium polish. Apply the polish to a polishing pad and work it into the aluminium surface using a back-and-forth motion. Ensure that the pad is in full contact with the surface to maximise the polishing effect. For best results, polish the boat at a low speed to prevent the polish from splattering.

Step 4: Wet Sanding

Wet sanding is the process of sanding the aluminium surface with sandpaper and water to remove any imperfections and prepare it for a final polish. Start with a lower grit sandpaper (around 120-500) and gradually work your way up to a finer grit (800-2000). Use vegetable oil on the sandpaper during this process to achieve a shiny finish. You can also use a dual-action polisher with foam pads for more effective results.

Step 5: Final Touches

Once you have achieved the desired level of shine, you may want to apply a wax or sealant to protect the finish. XPS Wax and Sealant can be used on painted hull surfaces. For bare aluminium, you may need to treat the surface with a protective coating to prevent oxidation and discolouration. Regular maintenance, such as rinsing the boat after each use and periodic cleaning with aluminium cleaner, will help maintain the exterior's pristine condition.

Removing corrosion

Corrosion is a common issue for aluminium boats, and it's important to take steps to prevent and address it to maintain the boat's condition and protect its value. Here are some detailed instructions for removing corrosion from an aluminium boat:

Identify the Type of Corrosion

Before starting the removal process, it's crucial to identify the type of corrosion affecting your boat. The most common types of corrosion in alloy boats include galvanic corrosion, crevice corrosion, and electrolytic formations. Galvanic corrosion occurs when aluminium comes into contact with dissimilar metals in an electrolyte such as saltwater. Crevice corrosion happens at the junction of two metal surfaces, especially in crevices or tight spaces. Electrolytic formations occur on the surface of unprotected metal immersed in an electrolyte. Understanding the type of corrosion will help you choose the most effective removal method.

Clean the Boat's Surface

Start by thoroughly cleaning the boat's surface to remove any dirt, grime, or oxidation. Use a special marine cleaner and a soft towel or cloth to wipe down the boat. You can also use a pressure washer or a clay bar to remove tough contaminants like tar or tree sap. Ensure that you clean both the exterior and interior surfaces, paying close attention to areas that are prone to corrosion, such as rivets, washers, and bolts.

Remove Corrosion with Abrasive Methods

For small areas of corrosion, you can use abrasive methods to remove the affected material. Sanding, wire brushing, or grinding can be effective in removing corrosion and restoring the aluminium surface. However, it's important to be cautious when removing structural material, as thinning the metal can compromise its integrity. Always work carefully and consider using a protective coating after corrosion removal to prevent further corrosion.

Apply Chemical Treatments

There are chemical treatments available that can improve the resistance of aluminium to corrosion. Products like alodine, zinc chromate paint, or a surface treatment like Alodine 1200 can help prevent further corrosion. These treatments should be applied after thoroughly cleaning and drying the surface. Always follow the manufacturer's instructions and take the necessary safety precautions when working with chemicals.

Use Sacrificial Anodes

Sacrificial anodes are an effective way to protect aluminium from corrosion. By attaching zinc sacrificial anodes to the aluminium, you can create a protective barrier that slows down the corrosion process. Ensure that the anodes are securely fastened and have good electrical contact with the aluminium surface. Regularly inspect and replace the anodes as needed, typically once a season or when they are halfway gone.

Prevent Future Corrosion

To prevent corrosion from recurring, it's important to take preventative measures. Always rinse your boat with fresh water after each use, especially if it has been exposed to saltwater. Apply protective coatings or paint designed for aluminium, such as copper-free, aluminium-compatible bottom paint. Regular maintenance and inspections will help you identify and address any signs of corrosion early on.

Polishing process

Achieving a mirror finish on an aluminium boat is a challenging task that requires meticulous attention to detail and a lot of patience. Here is a step-by-step guide to the polishing process:

Clean the Boat's Surface:

Start by thoroughly cleaning the boat's surface to remove any dirt, grease, or contaminants. Use a special cleaner, powerful degreasers, and a soft towel to ensure the surface is free from any impurities.

Contaminant Removal:

Use a clay bar specifically designed for marine applications to remove embedded contaminants such as dirt, grime, and oxidation. Lubricate the surface, then gently glide the clay bar back and forth to lift and remove the contaminants. After claying, rinse the boat thoroughly to remove any residue.

Apply Marine Aluminium Polish:

Choose a high-quality marine aluminium polish, such as 3M, and apply it to a polishing pad. Use a back-and-forth motion when applying the polish to the boat's surface, ensuring the pad is in full contact with the aluminium. Set the polisher to a low speed to prevent splattering and maintain control.

Wet Sanding:

Use wet sanding with 2000-grit sandpaper to smooth out any imperfections and prepare the surface for a mirror finish. This step is crucial for achieving the desired smoothness for a mirror shine. Use small pieces of sandpaper for better control, and focus on removing sanding marks effectively.

Select the Right Tools:

Choose a dual-action polisher with a foam pad to enhance the polishing process without damaging the surface. Experiment with different pad and compound combinations to find the best match for your boat's condition and desired finish.

Hand Polishing:

For hard-to-reach areas or more control, try hand polishing using a microfiber rag and a small amount of marine aluminium polish. Use circular motions and work on one section at a time to ensure thorough polishing. Regularly inspect the surface for consistency and adjust your technique as needed.

Protect the Finish:

Consider applying a protective coating, such as Sharkhide, to preserve the mirror finish and prevent oxidation. This step will help maintain the shine and reduce the need for frequent polishing.

Remember, achieving a flawless mirror finish on an aluminium boat takes time and dedication. Always follow safety precautions when working with chemicals and power tools, and don't be afraid to experiment with different techniques to find what works best for your boat.

Wet sanding technique

Wet sanding is a technique used to refine and smooth the surfaces of materials, in this case, your boat's gel coat. This technique is less abrasive than dry sanding and provides a smoother finish. It is important to understand when to wet sand your boat, and what tools and materials are needed.

When to Wet Sand Your Boat

Deep, visible scratches and severe oxidation with pitting are signs that your boat may benefit from sanding. It is ideal to engage in this process during the off-season or when your boat is not in regular use, allowing ample time for the task.

Tools and Materials Needed

• Electric RA (random orbital) or DA (dual-action orbital) sander
• Sandpaper with various grit levels (400, 600, 800, 1000, 1500, 2000) in the correct size disc to fit your sander
• Foam interface pad to be placed between the sander backing plate and the sanding disc
• Reliable water source
• Quality water spray bottle
• Masking tape to protect areas not being sanded

The Wet Sanding Process

• Fill a quality spray bottle with water and a few drops of liquid dish soap for lubrication.
• Set up your chosen sander with a new foam interface pad and the desired grit sanding pad.
• Ensure your extension cord connections are not in an area where they will sit in water and electrocute you.
• Clean the surface thoroughly and use masking tape to protect areas that do not need to be sanded.
• Begin with the coarse grit disc, applying light and even pressure while keeping the area wet with your spray bottle mixture.
• Rinse your sanding area and pad often to prevent a build-up of gel coat slurry, which will hinder the sanding process.
• Change your sanding discs frequently as gel coat can quickly dull sandpaper.
• Repeat the process with progressively finer grit until you reach a 1500-2000 grit finish.
• After each sanding phase, check your work to ensure you are progressing as expected and are not digging too deeply or unevenly.
• Once satisfied, wash the entire area or boat with soap and water to remove any residue.
• Compound out the scratches left by sanding, using a compound that removes the level of scratches indicated on the final grit used.
• Remove all holograms left by compounding with a finer polish and a softer wool/foam pad.
• Seal or wax the entire boat or area once the desired finish is achieved.

Common Mistakes to Avoid

• Over-sanding: Gel coat has a limited thickness, and sanding too much can decrease this thickness. Only sand as much as needed to remove defects.
• Patience and attention to detail are critical to achieving the best results.

Safety Tips for Wet Sanding

• Wear protective gear such as gloves and goggles to safeguard against potential hazards.
• Ensure your work area is well-ventilated, and take breaks to avoid fatigue.

Maintaining a bare aluminium hull

Cleaning and Drying:

Firstly, it is important to clean and dry your aluminium boat after each use, especially if it has been exposed to salt water or travelled over salty roads. Rinse the boat with fresh water and wipe away any visible scum or residue around the hull with a wet rag. Dried scum can be challenging to remove and may eventually stain the hull, so it is best to address this immediately.

Regular Maintenance:

Periodically, it is a good idea to give your aluminium hull a more thorough cleaning. You can use a mild detergent or a specialised aluminium cleaner, like XPS Aluminium Cleaner, with warm water. Avoid abrasive cleansers or solvents that could damage the finish of your boat. You can also use a mixture of water and vinegar for this step, which will help prevent corrosion.

Protecting the Hull:

To maintain the finish of your bare aluminium hull, you may want to consider applying a protective coating. A marine-grade clear coat can be an effective way to spot and repair any nicks or corrosion. Additionally, applying wax and sealant to the hull can help preserve its original finish and protect it from the elements.

Fuel Tank Care:

If your boat has aluminium fuel tanks, proper maintenance is crucial. Ensure that any paint applied to the tanks is done correctly, and regularly check for and remove any moisture under the paint. Use stainless steel washers or adapters in the boat fuel system fittings to prevent moisture and galvanic corrosion. It is also important to keep the tanks dry by draining water from all sides after each use.

Outboard and Trailer Maintenance:

Don't forget to maintain the trailer components, such as brakes, springs, and hubs, as per the boat manufacturer's recommendations. Additionally, after each use, flush the boat motor with fresh water to prevent salt buildup and corrosion.

By following these detailed instructions, you can effectively maintain a bare aluminium hull, ensuring the longevity and optimal performance of your boat.

Frequently asked questions