How to Repair a Polyethylene Agricultural Sprayer Tank

Polyethylene spray tanks are prone to crack either from getting dropped or from freezing temperatures. This tank is one that mounts to the back of an ATV. The tank was dropped and developed a crack. It also developed a crack that the owner tried to repair unsuccessfully with an adhesive. This will be an easy repair.

Most agricultural spray tanks (and those made for ATVs) are made from polyethylene. This is because nothing will react with polyethylene; it is very stable. Solvents don't affect it.

Polyethylene tanks have low surface energy so liquids (and adhesives) have a difficult time "wetting out" on the surface. Putting an adhesive on polyethylene is like putting water on a freshly waxed car. The adhesive wants to "bead up" on the surface. The only way to permanently repair the polyethylene chemical spray tanks is to weld the plastic as shown here.

We make this repair with a hot air plastic welder and some polyethylene welding rod (we used LDPE welding rod, but HDPE rod can be used).

View this step-by-step repair photo series here.

This kind of repair can be done using a hot air plastic welder or a nitrogen plastic welder (we have several nitrogen plastic welders available).

See the benefit of using hot nitrogen over regular hot air here!

Always wear proper safety gear while working!

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Products Used:

Note: This is a list of the Polyvance products that can be used to make this repair. This list does not include sanders, grinders, or other common tools you will need. If you have any questions, please don't hesitate to call technical support at 800-633-3047.

• 1000 Super Prep Plastic Cleaner (several options available) OR 1001-4 EcoPrep Plastic Cleaner
• 6121-T Tear Drop Cutter Bit
• Hot Air Welder OR a Nitrogen Plastic Welder (several options available)
• Low Density Polyethylene Welding Rod (you can also use High Density Polyethyelene welding rod)

Video Notes:

• Super Clean plastic cleaner has been renamed Super Prep.
• English Closed Captions have been provided for this video. Click on the CC button to turn them on or off.
• The length of this video is in no way representative of the actual time required to perform a complete repair and therefore should not be used for estimating purposes.

English Transcript:

Polyethylene spray tanks are prone to crack either from getting dropped or from freezing temperatures. This tank is one that mounts to the back of an ATV. The tank was dropped and developed a crack, although the crack is difficult to see here. It also developed a crack that the owner tried to repair unsuccessfully with an adhesive. This will be an easy repair.

Clean the damaged area as well as you can with Super Clean Plastic Cleaner.

Use a rotary tool with a teardrop-shaped cutting bit to create a v-groove and to grind away any crusty, oxidized plastic.

When this tank was accidentally dropped, the plastic got stretched and deformed from the impact. Soften the plastic with the hot air plastic welder and use something like a screwdriver handle to push the plastic back into shape.

The plastic on this tank was thinner than we expected, and we accidentally cut a hole into the plastic with the rotary tool. It's not a problem, though. Just use a wider strip of polyethylene to bridge the gap. Make several passes with the strip to not only bridge the gap, but also to make the plastic thicker and stronger. You may want to smooth out the weld and melt down any curl to edges with an airless plastic welder.

As soon as the plastic cools off, it will be ready for use. You can speed up the cooling with compressed air if you want to.

To repair the crack, clean the plastic then remove a thin layer of oxidized, crusty plastic along the crack line with a rotary tool and a teardrop shaped cutting bit.

Lay down several passes of polyethylene welding strip to repair the crack and get it extra strength. While the plastic is still hot, use an airless plastic welder to melt down any curl to edges.

After all the plastic cools off, test the tank for leaks.