Hydrochloric acid (HCI) is powerful, toxic, and highly corrosive. According to research, HCl is responsible for at least one-third of the fatal accidents caused by chemical spills. For this reason, the most commonly recommended solution for storing hydrochloric acid is a robust poly storage tank with secondary containment.

HCl, also known as muriatic acid, is an important part of many manufacturing processes. HCI applications are common in the food industry, as well as oil well acidizing, steel pickling, and chemical production regularly use the substance. Neutralizing basic solutions, maintaining pH levels in swimming pools, and ore reduction of tin and tantalum.

Hydrochloric Acid Storage Tank Requirements

HCl Properties

Hydrochloric acid is a clear, colorless, and highly pungent solution of hydrogen chloride in water with 36.46 g/mol molar mass and 1.18 g/cm3 density. HCl is a strong acid that is completely dissociated in water.

HCl Fume Mitigation and Storage Guidelines

Due to its volatile nature, HCl is a government-regulated air pollutant and comes with its own storage challenges. HCl vapors and fumes can be corrosive to other materials and harmful for those who inhale them. Important considerations include:

• Production of HCl gas can cause hazardous buildup if you store it incorrectly or in a sealed container.
• Bulk HCl storage needs fume vents and scrubbers for safe storage and handling. HCl fume systems use thermoplastics and fiberglass reinforced plastic (FRP) materials.
• Store HCl away from direct sunlight, heat sources, and other incompatible materials.
• Use airtight connections and manways and fume scrubbers and vents to reduce HCl fumes.
• Application lines and service ways should be made of HCl-resistant material to prevent damage to connections or structural failure of storage systems.
• Transfer or transport of hydrochloric acid requires fume or pressure dissipation to reduce increased vapor pressure.

Refer to the information on storage, transportation, and disposal of HCl in the Occupational Safety and Health Act (OSHA) and the Environmental Protection Agency (EPA) 40 CFR 261.22.

Types of HCl Acid Storage Tanks

Polyethylene HCl Acid Storage Tanks

Polyethylene, or poly tanks, are made of cross-linked polyethylene (XLPE), high-density polyethylene (HDPE) or low-density polyethylene (LDPE). Chemically resistant XLPE tanks are cost-effective, and the most commonly recommended solution for hydrochloric acid storage.

We recommend that you use multiple tanks if the quantity of acid storage exceeds 12,500 gallons. The acid storage tanks should have a specific gravity rating of 1.9, polyvinyl chloride (PVC) fittings, Viton® gaskets, and Hastelloy bolts. The temperature of its contents should never exceed 100 degrees fahrenheit.

HCl Fiberglass Reinforced Plastic (FRP) Tanks

An FRP hydrochloric acid storage tank has a high strength-to-weight ratio with a long lifespan and low cost of maintenance. They come lined with a corrosion-resistant barrier and are resistant to

HCl corrosion and mechanically durable against the pressure stress caused by hydrochloric acid vapors during transfer.

Proper construction and regular inspection are important for FRP tanks with a hydrochloric acid-resistant resin and corrosion barrier.

Rubber-Lined Steel HCl Acid Storage Tanks

Rubber-lined steel tanks are a preferred choice for hydrochloric acid storage of more than 15,000 gallons in a single unit. They are also preferred when there is a potential threat of damage to poly tanks from the movement of mechanical equipment on-site.

However, steel tanks with rubber linings are the most expensive to set up and maintain. Remember, steel is susceptible to hydrochloric acid corrosion, which can produce hydrogen gas, a highly flammable, explosive, and corrosive material.

Steel tanks for hydrochloric acid storage use ASTM-283 Grade C steel or equivalent. The interior rubber lining that holds liquid should be at least 3/16 of an inch in thickness and be able to withstand a maximum temperature of 160°F.

Polypropylene HCl Tanks

Polypropylene hydrochloric acid storage tanks are fit for small quantities of up to 45 gallons and are effective only if the muriatic acid concentration is less than 20 percent. Polypropylene tanks begin to lose their resistance if the muriatic acid concentration exceeds this level.

HCl Storage Tanks: Components and Resistance Levels

Hydrochloric acid storage tanks come in various materials. Apart from the tank body, you also need to consider the material of other components such as the pipes, PVC fittings, Hastelloy-C bolts, and Viton® gaskets.

Here are some plumbing precautions, assuming it is a vertical HCl acid storage tank:

• Install flexible plumbing connections to the storage tanks
• Allow up to 4 percent lateral and vertical expansion of the tank
• Reduce pump and piping vibration stress
• The structural support for flexible connections, piping, and valves must be independent of the tank sidewall and dome

Transportation and Disposal of HCl Acid

You should always transport hydrochloric acid in secure double-walled tanks to prevent spills and leakage. Transport HCl acid at room temperature to reduce pressure buildup.

Listed below are some basic guidelines for HCl storage:

• Keep acid away from incompatible substances, such as oxidizing agents, organic materials, metals, and alkalis
• Keep the container securely closed at all times
• Store the acid in a cool, well ventilated, dry area and away from moisture

Spilled HCl is hazardous waste and a qualified contractor is required for disposal. View all the regulations at federal or state government resources on hydrochloric acid.

FAQs

Can you store HCl acid in plastic?

• Yes, tanks made of specialized plastics, such as polyethylene (XLPE, HDPE, or LDPE) or fiberglass reinforced plastic (FRP) can store hydrochloric acid.

What is the storage requirement for HCl?

• We recommend that you do not store more than 12,500-gallons of concentrated hydrochloric acid in a single poly tank. If you need more high-capacity storage, use a multiple-tank system. Storing large quantities of hydrochloric acid can cause hazardous vapor buildup. Therefore, you need vents or fume scrubbers, which is the EPA-approved method for mitigating HCl fumes.
• Also, perform regular inspections of the tank material and accessories such as PVC fittings, Viton® gaskets, and Hastelloy bolts. Be sure to store hydrochloric acid in a cool, dry place away from other reactive materials.

What are the temperature limits on various HCl Storage Tanks?

• XLPE tanks can withstand temperatures of up to 100°F. However, it is recommended not to use XLPE tanks once they have been exposed to 150°F to avoid problems in the future. HCl steel tanks have an internal rubber lining that should withstand 160°F.
• Polypropylene tanks are not recommended for use below freezing temperatures. Common HCl freezing points show that freezing is not a general concern.