Repairing Pitting On Your Aluminum Boat: A Step-By-Step Guide

Pitting is a type of corrosion that occurs on aluminium boats, causing small holes to form in the metal. This is caused by a process called depassivation, which involves the deterioration of protective coatings around the metal due to contact with a chloride. Saltwater is the main culprit for pitting on aluminium boats.

There are several methods for removing pitting from aluminium boats, including dry and wet sanding, using a razor blade, and filling pits with an aluminium filler or putty. After removing the pitting, it is important to polish and protect the aluminium surface to prevent further corrosion. This can be done using an aluminium polish and sealer.

In addition to removing pitting, it is important to address the cause of the corrosion. This may involve changing the type of lumber used for bunk boards, adding a Perko switch to turn off batteries, or grounding all electronics back to the battery.

Wash the aluminium surface with a mild alkaline soap

To fix pitting on an aluminium boat, it is important to wash the aluminium surface with a mild alkaline soap. Here is a detailed, step-by-step guide:

Firstly, it is crucial to understand the causes of pitting on aluminium boats. Pitting is a form of corrosion that occurs when the protective coatings around the metal deteriorate due to contact with chlorides, particularly saltwater. As a result, small holes form in the metal, leading to leakage and further damage. Therefore, it is essential to address pitting as soon as it is noticed.

The first step in the repair process is to thoroughly rinse the aluminium surface to remove any dirt, grime, or residue. This can be done using a power washer or a hose. Ensure that you blast away all the dirt and grime, especially in the pitted areas, to create a clean surface for the next steps.

Next, it is important to choose the right soap for washing the aluminium surface. Mild alkaline soap is recommended as it will effectively clean the metal without causing further damage. Avoid using common dish soap, as it often has high alkaline levels that can strip the wax off the surface. Gently wash the aluminium with the mild alkaline soap, ensuring that you cover all the pitted areas.

Once you have finished washing the aluminium, it is crucial to dry the surface thoroughly. Use a microfiber towel or a soft, clean cloth to absorb any remaining moisture. Make sure that the surface is completely dry before moving on to the next step.

After drying the aluminium surface, you may need to remove any remaining corrosion. This can be done through various methods, such as dry sanding, wet sanding, or using a razor blade. Choose the method that best suits the severity of corrosion and your personal preference. Remember to work carefully and wear appropriate protective gear during this step.

Finally, once the corrosion has been removed, buff the sanded area using a rotating buffer or fine steel wool until the surface is smooth and free of all pitting. If necessary, repeat the sanding and buffing process until you achieve the desired result. Finish by wiping the area with a clean microfiber towel to remove any remaining debris.

By following these steps and choosing the right products, you can effectively wash the aluminium surface with a mild alkaline soap and make significant progress in repairing pitting on your aluminium boat. Remember to work carefully, wear protective gear, and seek professional advice if you are unsure about any part of the process.

Remove corrosion with dry or wet sanding

To remove corrosion from an aluminium boat, you can use dry or wet sanding.

Dry Sanding

Begin with a higher grit (200-400) sandpaper and work your way to a finer grit (600-800). Use the more abrasive sandpaper to remove the deep pits, and then switch to the finer paper. Do two or three rounds of sanding, using a finer grit than the last for each round.

Wet Sanding

Wet sanding is preferred by some as it does not produce as much dust and does not clog the sandpaper as often as dry sanding. For this method, use sandpaper specifically for wet sanding (dry sandpaper will fall apart). Start with a grit of around 200-400, mix a bowl of water with a few drops of dishwashing liquid, wet the paper, and sand the pitting off the aluminium. Finish using a fine grit of around 600-800, just like the dry sanding method.

General Tips for Sanding

• Before you start sanding, prepare your workspace and tools. Cover your work area with a drop cloth or newspaper to protect it from scratches and debris.
• Ensure you have all the necessary tools and materials, including sandpaper, a sanding block, a bucket of water, and safety gear such as goggles and gloves.
• When using wet and dry sandpaper on metal, selecting sandpaper suitable for both wet and dry sanding is essential. Wet and dry sandpaper is made with waterproof backing material, which allows it to be used with water or other liquids to reduce friction and prevent clogging.
• Always start with a coarse grit and work up to a finer grit.
• Use light pressure when sanding to avoid creating deep scratches or dents.
• Keep the sandpaper and metal surface wet during wet sanding to prevent clogging and reduce heat buildup.
• Check your progress frequently to ensure you’re achieving the desired level of smoothness.
• Take your time and be patient—sanding metal can be time-consuming, but the results are worth it!

Buff the sanded area with a rotating buffer or fine steel wool

Buffing is the process of smoothing out the surface of the metal to remove any scratches or imperfections. It is an important step in the finishing process, as it helps to create a uniform and consistent appearance.

When using a rotating buffer, it is important to work in small sections and follow the direction of the grain of the metal. Start with a low speed and gradually increase it as you work. Apply light pressure and move the buffer back and forth across the surface until the desired finish is achieved. You can use a polishing compound with the buffer to help achieve a smooth and shiny surface. Make sure to wear appropriate safety gear, such as eye protection and gloves, when using a rotating buffer.

If you are using fine steel wool, it is important to soak it in water before use to prevent the steel wool from shedding and leaving bits of metal in the aluminum. Rub the steel wool back and forth over the sanded area with light pressure until the surface is smooth and free of scratches. Fine steel wool is a good option for reaching tight spaces and curved surfaces that may be difficult to access with a rotating buffer.

Both methods will help to create a smooth and consistent finish on the aluminum, which is important for achieving a high-quality final product. It is important to take your time and work carefully to ensure the best results.

Polish and protect the aluminium surface

Once you've removed the corrosion from your aluminium boat, it's time to polish and protect the surface. Here are the steps you should follow:

Start by rinsing off all the dirt from the aluminium surface. You can use a power washer to blast away grime or a hose.

Next, wash the surface with a mild alkaline soap. Avoid using common dish soap, as it may have high alkaline levels that can strip the wax off the surface. After washing, thoroughly dry the surface with a microfiber towel.

Now, it's time to smooth out the aluminium surface. You can use a rotating buffer or fine steel wool to buff the area until it appears smooth and free of all pitting. If there are still some problem spots, repeat the sanding process. Finish by wiping off all debris with a clean microfiber towel.

Once the surface is smooth, it's time to apply an aluminium polish and sealer using a clean cloth. This will not only brighten the surface but also defend it from further oxidation and pitting. BoatLIFE's aluminium cleaner is a popular option.

After polishing, it's essential to protect the aluminium surface from future corrosion. You can use a marine-grade wax or a specialised aluminium protectant to create a barrier against the elements. Make sure to follow the manufacturer's instructions for proper application.

Remember to inspect your boat regularly for any signs of corrosion and treat it promptly to prevent further damage.

Apply an acid wash to prevent future corrosion

Acid washing is a process used to remove mill scale and any other oxides that have formed on the surface of the aluminum. It involves the use of an acid solution, such as phosphoric and hydrofluoric acids, to etch away the surface layer of the metal, exposing the underlying parent metal. This process is often followed by rinsing with water and then treating with a zinc and chromium solution to form a protective Chromium Oxide film, which can help prevent future corrosion.

To acid wash your aluminum boat, you will need to purchase an acid solution designed for use on aluminum. Some products that have been mentioned in online forums include Zep-a-Lume, Alum-a-Brite, Alumiprep, and Alodine. You should follow the instructions provided with the product you choose, but in general, the process will involve applying the acid solution to the surface of the boat, allowing it to etch away the surface layer, and then thoroughly rinsing the boat with water to remove any remaining acid. It is important to note that acid washing can be dangerous, so be sure to wear appropriate protective gear and take the necessary safety precautions.

After acid washing, you may want to consider applying a protective coating, such as a wax or polish, to further protect your boat from corrosion. Additionally, keeping your boat clean and dry can also help prevent corrosion.

Frequently asked questions