Safely Storing Sodium Hydroxide in Chemical Storage Tanks

Sodium hydroxide, also known as lye or caustic soda, is used to neutralize the pH of water in a variety of applications. The chemical leaves no residual color, is a high-strength product, and is available at concentrations of two to 50 percent. Most of our customers use it in 25 to 50 percent concentrations.


Sodium hydroxide has a wide variety of uses such as making paper, water treatment, medicine and even food preparation. It can be found in many household items such as drain cleaner, detergents, and bath soaps. While this chemical is widely used, its properties present special storage and handling challenges.

Sodium Hydroxide Storage Challenges

At room temperature, sodium hydroxide is a white solid that can be found in flakes, granules, or pellets. In liquid form, it is colorless and denser than water. It also becomes slippery and tends to find weak points in storage containers, which can result in leaks. When dissolved in water or neutralized with acid, it releases substantial amounts of heat, which may prove sufficient to ignite combustible materials.

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In all forms, sodium hydroxide is highly corrosive and reactive. As a solution, it will react with many metals, including aluminum, magnesium, copper, and zinc. It also reacts readily with organic tissue such as human skin or eyes. Exposure to sodium hydroxide, even if only for a few seconds, can result in permanent eye damage and severe chemical burns. For this reason, it is critical to ensure that caustic soda is handled and stored properly.

When evaluating your storage options, make sure you consider these two crucial elements:

  • Secondary containment – Because of the potential hazards involved, secondary containment is an absolute environmental and safety priority.
  • Temperature – If sodium hydroxide is not stored at temperatures above 60° F, the chemical may crystalize and turn solid, resulting in unnecessary chemical waste and damage to the storage system itself.

How Should Sodium Hydroxide Be Stored?

While there are many options for Sodium Hydroxide storage, a rotationally molded cross-linked polyethylene tank is ideal. This process produces a seamless tank, making it nearly impossible for the chemical to find leaks.

SAFE-Tank® System

Because of its hazardous and highly corrosive nature, it is important to have a double-wall containment system for caustic soda. If a double-wall tank system is required, Poly Processing’s SAFE-Tank system is a “tank within a tank” that allows for greater safety by offering secondary containment that is completely enclosed.

View our SAFE-Tank installation page

The SAFE-Tank systems provide at least 110 percent containment within the same footprint as a vertical storage tank, making it easy to store the chemical wherever it’s most efficient and convenient. In addition, the tank's high-density XLPE construction means greater strength and longer life. It’s so strong that Poly Processing Company offers a five-year full warranty.

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IMFO® Tank System

It’s also important to consider the tank fittings. Poly Processing’s IMFO® Tank fitting is an ideal choice, because the flange is actually a molded part of the tank itself, rather than an insert that could leak or fail. The IMFO fitting also ensures long-term performance of the overall system, because it eliminates the need to drill into the tank's sidewall to install a mechanical fitting.

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Our Integrally Molded Flanged Outlet (IMFO®) Tank is a homogenous flange system that is molded as part of the tank while it is being manufactured, making it a stress-free part of the tank. The flange is created from the same material as the tank — it’s not an insert added during or post-production.

Some companies create tanks out of one substance and insert a metallic flange post-production, for drainage and discharge. This is simply to save money on investing in proper tooling to make the right tank. An inserted metallic flange unfortunately is common in the tank industry, but there are critical benefits to using a molded full discharge fitting or IMFO.

Check out our Sloped Bottom Tanks with IMFO

Advantages of the IMFO Tank include:

  • Full tank discharge, because the flange is at the bottom of the sidewall, below the tank knuckle radius. There’s no need to enter the tank for cleaning.
  • Enhanced long-term performance and fuller useful life of the tank since the flange doesn’t compromise the tank’s hoop integrity or structural design.
  • Complete flange face protection is available in aggressive oxidation environments. The antioxidant OR-1000™ system can protect the discharge components from deterioration.
  • Highest amount of static head pressure. The IMFO’s design brings you the highest net positive suction head (NPSH) of any vertical non-coned tank on the market.
  • Any required maintenance is simple and hassle-free. Unlike metallic inserts, the flange extends away from the tank wall and the entire flange system is external with easy hardware access from outside the tank.
  • There are no chemical compatibility issues like the ones you may encounter with metallic inserts. If the chemical is safe in a crosslinked polyethylene tank, it’s safe discharging out of the IMFO system.

If you already have concrete containment in place at your facility, the IMFO Tank is our recommended tank system for storing Sodium Hydroxide.

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Temperature Regulation

Whatever tank configuration you choose, it will be important to maintain proper temperatures inside the tank. For polyethylene chemical storage tanks, heating pads and insulation can maintain the specific temperature of the chemical you’re storing—even when your chemical tank is exposed to low air temperatures.

Poly Processing’s chemical tank heating system comprises tank heating pads and a temperature controller with thermostat. The quantity and size of the silicone heating pads depend on the size of the tank, the required chemical temperature, and ambient environmental conditions.

Learn more about sodium hydroxide storage — Download our sodium hydroxide chemical storage guide.

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