Sylvie Willis
Poly fuel tanks are notoriously difficult to repair because of the nature of the plastic they are made from. Polyethylene (PE) is highly resistant to chemical attack and nothing tends to stick to it. However, there are some methods that can be used to repair them, such as using a sealant or adhesive, welding, or a mechanical patch. Some products on the market, such as TankWeld™, Seal-All, and Permatex, are designed to repair fuel tanks, but these may not be suitable for all types of plastic tanks. In some cases, it may be necessary to replace the tank entirely.
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What You'll Learn
Using adhesives to repair a poly fuel tank
Poly fuel tanks are made from HDPE plastic (High-density polyethylene). Most PE plastic grades have excellent chemical resistance, meaning they are resistant to strong acids, strong bases, gentle oxidants, and reducing agents. This makes polyethylene challenging to repair using adhesives.
However, some adhesives can be used to repair cracks in poly fuel tanks. One option is to use a two-component epoxy glue. Before applying the glue, the surface should be sanded and cleaned with acetone. However, it is important to note that epoxy glue is rigid and not elastic, so it may crack when the fuel tank expands and contracts.
Another option is to use a product like Tech-Bond, which offers different adhesive types with varying viscosities and strengths. Their Green Adhesive is ideal for repairing small cracks, while their Blue Adhesive offers improved control while maintaining good wicking and strength characteristics.
Additionally, G-Flex sealant is reported to work well on PE, approaching the strength of a weld if applied correctly. To use G-Flex or similar adhesives, the process involves:
- Cleaning the surface.
- Sanding with 80-grit sandpaper.
- Flaming the surface with a torch to denature the plastic—do this gently, just enough to make the surface dull without melting it.
- Bonding a fabric patch (e.g., Sunbrella) with an overlap of about 1 inch using the adhesive.
It is important to note that some common adhesives, like superglue, may not be suitable for repairing poly fuel tanks. Additionally, 3M sealants are reported to not work well on PE. Therefore, it is essential to choose an appropriate adhesive designed for use with polyethylene and follow the manufacturer's instructions for the best results.
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Sanding and cleaning the tank before applying adhesive
To repair a poly fuel tank, you must first drain the tank and let it dry completely. Next, sand the area around the hole or crack with medium-grit sandpaper. Sanding is an essential step as it cleans the area, allowing the adhesive to bond better with the tank. It also fills the crack, so when heat is applied, it helps to fill the crack better.
Use coarse-grit sandpaper to sand around the problematic area. You can use medium-rough sandpaper for this. Make sure to sand the perimeter of the area to be repaired. Sanding the area ensures that the adhesive compound can adhere properly. Once you have finished sanding, clean the area with a cloth soaked in rubbing alcohol.
After sanding and cleaning, you can apply heat to the tank using a soldering iron. Set the temperature between 250-300 degrees Celsius, using a wider solder tip of around 1 cm to help dissipate the heat evenly around the crack. If more of the surrounding area is heated, the plastic will bond better to the tank.
Once you have applied heat, you can begin to apply the adhesive.
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Drilling the crack to prevent it from spreading
Drilling the crack is a common method to prevent it from spreading further. This technique is especially useful when dealing with cracks in poly fuel tanks, which are notoriously difficult to repair due to the challenging nature of bonding with polyethylene (PE) plastic.
The process of drilling the crack involves using a tiny drill bit to create holes at both ends of the crack. This technique relieves stress on the crack, preventing it from lengthening. It is important to ensure that the tank is completely empty and cleaned before drilling, as fuel vapors are highly flammable.
After drilling, one method is to use a soldering iron to weld the crack shut. This involves applying heat to the area, melting the plastic, and allowing it to meld back together. It is crucial to control the heat carefully to avoid warping or further damaging the tank.
Another approach is to use a mechanical patch. This involves roughening the surface around the crack with sandpaper, creating a better bond for the patch. A plastic stick, melted with a soldering iron, can be used to fill and seal the crack.
While these methods can provide temporary solutions, repairing a poly fuel tank is generally not recommended due to safety concerns. Gasoline is dangerous, and the repair may not meet safety standards. It is important to regularly monitor the tank for any signs of leakage or weakening after a repair.
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Applying heat to the tank to repair a crack
To repair a crack in a poly fuel tank, one method is to apply heat to the tank. This process is also known as plastic welding. It is important to note that this method is more of a temporary fix and may not be suitable for extensive damage. Here is a step-by-step guide on how to apply heat to repair a crack in a poly fuel tank:
Prepare the Tank
Start by emptying the fuel tank and leaving it open to prevent pressure buildup. Clean and dry the area around the crack to ensure that there is no fuel residue or moisture that could interfere with the repair process.
Sand the Area
Use medium-grit sandpaper (around 60-grit) to sand the area around the crack. Sanding serves two purposes: it cleans the area, allowing for better adhesion, and it helps to fill the crack by creating sanding debris. Ensure that the area is sufficiently sanded and free of any dirt or grease.
Apply Heat
Take a soldering iron or a plastic welding iron and set it to a temperature between 250-300 degrees Celsius. Use a wider tip (approximately 1 cm) to dissipate heat evenly around the crack. Apply heat to the tank, being careful not to melt through the tank. Only melt a thin layer of plastic and work it into the crack.
Use Filler Strips
Softening the area with heat will ensure good adhesion for the filler strips. Take filler strips, such as polyethylene (PE) plastic sticks, and apply heat to one side while pressing them into the softened area. Build up 1-2 layers until you match the thickness of the tank material, tapering for at least five tank thicknesses wide on each side of the crack.
Smooth the Layers
Use the welding iron to smooth the layers of plastic together, creating a uniform surface. Be careful not to linger too long in one area, as the heated plastic may begin to sag into the tank. Your goal is not to create a true fusion weld, as in steel welding.
Sand and Finish
Once the filler and tank have cooled, you can sand the repaired area with fine-grit sandpaper to smooth out any imperfections. If desired, you can use a light flame with a torch to restore gloss to the area. Ensure that the tank is thoroughly cured before refilling it with fuel.
Remember to work in a well-ventilated area and avoid open flames, as fuel vapors are highly flammable. Always prioritize safety when working with poly fuel tanks and follow manufacturer recommendations whenever possible.
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Using a repair kit for permanent or temporary fixes
Poly fuel tanks are made from HDPE plastic (High-density polyethylene) and are resistant to strong acids, strong bases, and gentle oxidants and reducing agents. Due to these properties, it is hard to fix them with glue. However, there are repair kits available that can be used to fix cracks and holes in poly fuel tanks. Here are the steps to use a repair kit for permanent or temporary fixes:
Step 1: Empty the tank from fuel and leave it open
Empty the tank from fuel and leave it open so that fuel will not create pressure inside the tank.
Step 2: Sand the problematic area
Use medium-rough sandpaper to sand around the problematic area. Sanding is necessary to clean the area and allow the PE plastic stick to bond better with the PE tank. It also helps to fill the crack inside.
Step 3: Apply heat to the tank
Take a solder iron and set it to a temperature between 250-300 Celsius. Use a wider solder tip of around 1cm wide to help dissipate the heat evenly around the crack. Apply heat to the tank and then remove the solder iron.
Step 4: Use a polypropylene welding stick
Plug in a polypropylene welding stick and melt it into the tank. You can also use a plastic stick and apply heat to it with the solder iron until it melts and bonds to the tank. Move along the crack in small increments, melting the stick along the way.
Step 5: Sand the repaired area
Once you have finished melting the stick along the crack, use sandpaper again to sand the repaired area. If some of the PE stick is not properly melted and bonded to the tank, it will fall off, indicating which areas need to be repaired again.
Using adhesives for repairs
Some sources suggest using adhesives like epoxy glue or super glue for repairs. However, it is important to note that epoxy glue is rigid and not elastic, so it may crack when the fuel tank expands and contracts. Super glue may also not be effective in bonding with the PE plastic. Stabilized adhesives, such as those offered by Tech-Bond, claim to provide a strong and fast cure regardless of the material. Their Blue and Green Adhesives are designed to work with a variety of materials and offer improved control and strength.
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Frequently asked questions
It is difficult to repair poly fuel tanks with sealants or adhesives as most substances do not stick to polyethylene (PE). However, you can try Permatex 2, which can be used as a sealant.
One alternative method is to weld the tank. You can use a soldering iron to apply heat to the crack and melt a plastic stick to fill it.
You can use a plastic stick made from HDPE plastic, cut to a width of 1 cm and a length of 10-15 cm. Wash and dry the plastic stick before use.
Empty the tank of fuel and leave it open to prevent pressure from building up. Sand the problematic area to clean it and allow the plastic stick to bond better.
You can use a mechanical patch for small holes. Tech-Bond offers a range of adhesives that can be used for repairs. TankWeld™ is another option, designed for permanent or temporary repairs of metal and fuel storage containers.
