What is a chemical resistant pump and how does it work?

A chemical resistant pump is a pressure pump built with materials specifically chosen to withstand the corrosive action of aggressive fluids, such as caustic soda, acids, solvents, demineralized water and salt water. In industrial applications the most common type is the high-pressure piston pump, where every wetted component, manifold head, valves, seals and pistons is made of corrosion-resistant materials like AISI 316L stainless steel, EcoBrass®, nickel plating, technical ceramics and special elastomers. The pump works on the same principle as a standard piston pump, three ceramic pistons alternately drawing in and discharging the fluid through one-way valves, but with internal parts that resist chemical attack over time. Hawk Pumps manufactures a complete range of chemical resistant pumps and a chemical pump for caustic soda applications, with operating pressures up to 200 bar and water temperatures up to 85 °C.

What a chemical resistant pump is

A chemical resistant pump is a pump engineered to handle aggressive liquids that would quickly damage a standard pump. The aggressiveness can be due to several factors: strong acidity or alkalinity (low or high pH), high chloride concentration (salt water), presence of solvents or surfactants, or simply the ion-stripping action of demineralized and osmotic water, which dissolves particles from unprotected metal surfaces.

Standard pressure pumps, typically with brass heads and carbon steel valves, last only a few weeks under these conditions. A chemical resistant pump, on the other hand, is designed for continuous use in the chemical, pharmaceutical, food, oil & gas, and marine industries, ensuring long service life, leak-free operation and operator safety.

How a chemical resistant piston pump works

The operating principle is identical to that of a standard positive-displacement piston pump. The cycle unfolds in two phases that repeat three times per crankshaft revolution (in the most common 3-piston configuration):

1. Intake: each piston retracts, the suction valve opens by depression, and the aggressive fluid enters the chamber through the corrosion-resistant manifold head.
2. Discharge: the piston advances, the suction valve closes, the discharge valve opens, and the fluid is pushed under pressure toward the application — a high-pressure cleaning lance, a chemical reactor, a CIP (Clean-In-Place) circuit, etc.

What makes the difference between a chemical resistant pump and a standard one is not the working principle but the choice of every internal component. Each material is selected to ensure chemical compatibility with the fluid handled, so that the pump retains its mechanical properties and zero-leakage performance even after thousands of operating hours.

Materials that make a pump chemical resistant

The pump's construction material is the single most critical factor when pumping aggressive liquids. Each component is engineered to resist a specific type of chemical attack:

For some applications, two materials can be combined in the same pump — for instance an EcoBrass® head with stainless steel valves, or a nickel-plated head with special seals — to optimize chemical compatibility with the specific fluid handled.

Chemical pump for caustic soda and other aggressive liquids

Caustic soda (sodium hydroxide, NaOH) is one of the most demanding fluids a pump can handle: a strong base with pH between 13 and 14, with a specific gravity of about 1.52 at 50% concentration and extremely corrosive on aluminum, carbon steel and many polymers. It is widely used in:

• Tank, container and reactor cleaning in the chemical industry: removal of water-resistant paints, resins and glue residues that cannot be removed with water alone.
• CIP (Clean-In-Place) cycles in the food and pharmaceutical sectors: sanitation of production lines, tanks and pipelines.
• pH correction in water treatment plants and wastewater facilities.
• Pulp, paper, textile and detergent manufacturing processes.

A chemical pump for caustic soda must combine chemical resistance (to withstand the strong alkalinity), mechanical robustness (to handle the high specific gravity of concentrated NaOH solutions) and thermal stability, since caustic soda is often used hot. The same applies to other aggressive liquids: demineralized and osmotic water (which erodes unprotected metals by dissolving ions from the surface), acids (sulfuric, nitric, phosphoric in diluted form), solvents and salt water.

Hawk chemical resistant pumps

Hawk Pumps has developed a complete range of chemical resistant pumps dedicated to the chemical, pharmaceutical, food, marine and oil & gas sectors. The main series are:

• NMT-ES Stainless Steel: maximum pressure 200 bar, water temperature up to 85 °C. Manifold head and all internal metal components in contact with the fluid are made of AISI 316L stainless steel. Special seals enable use with aggressive chemicals and salt water. The reference solution for industrial and pharmaceutical reverse osmosis plants.
• NMT Chemical: maximum pressure 200 bar, maximum flow rate 21 l/min, head in EcoBrass®. Suitable for demineralized water, osmotic water and solvent applications. The non-ferrous composition provides superior wear resistance.
• NHDP Chemical: maximum pressure 200 bar, water temperature up to 65 °C, head in EcoBrass®. Designed for marine desalination and plants operating with chlorides.
• XLTI Chemical: maximum pressure 150 bar, water temperature up to 65 °C. A versatile solution for chemical washing and compact installations.
• NMT-HT (High Temperature): maximum pressure 150 bar, water temperature up to 85 °C, nickel-plated manifold. Designed for washing systems used in the food industry and applications with hot water.

For an in-depth analysis of material selection, Hawk has published a dedicated guide to choosing the best piston pumps for aggressive liquids.

How to choose the right chemical resistant pump

Selecting a chemical resistant pump requires a careful evaluation of five technical variables:

1. Type and concentration of the chemical: the higher the concentration and the more aggressive the fluid, the more sophisticated the materials must be (special alloys, nickel plating, fluoropolymer seals).
2. Operating temperature: temperature dramatically affects corrosion. AISI 316L stainless steel, for instance, performs well with dilute caustic soda at ambient temperature but is subject to caustic embrittlement above 60 °C in concentrated solutions.
3. Operating pressure: chemical resistant Hawk pumps cover the range up to 200 bar, sufficient for most cleaning, CIP and chemical-transfer applications.
4. Required flow rate: determined by the number of nozzles, the size of the surfaces to be cleaned, or the CIP cycle requirements.
5. Maintenance and access: chemical pumps benefit from designs that allow fast replacement of seals and valves, since these are the components subject to wear.

Chemical compatibility between fluid and pump components must always be verified against compatibility tables or when in doubt directly with the manufacturer.

Applications of chemical resistant pumps

Hawk chemical resistant pumps are used worldwide in:

• Internal cleaning of industrial containers: plastic or steel bins, jerry cans, cisterns, silos, tanks and chemical reactors contaminated with paints, resins, glues and similar substances.
• Food industry: sanitation of production lines with hot water and CIP detergents.
• Reverse osmosis for marine, civil and industrial desalination plants.
• Oil & gas: cleaning of pipelines, tanks and refinery equipment.
• Pharmaceutical industry: sanitation of reactors and process equipment with specific cleaning agents.

About Hawk Pumps

Hawk Pumps is the trademark of Leuco S.p.A., an Italian company founded in 1979 and based in Reggio Emilia, Italy. With more than 35 years of experience in high-pressure piston pump manufacturing, Leuco produces over 70 pump models, including a dedicated range of chemical resistant pumps for the most demanding industrial environments. The company has been ISO 9001 certified since 2000, ISO 14001 certified for environmental management and ISO 50001 certified for energy management. Leuco has been part of the Kärcher Group since 2004.

Related questions

Can a Hawk pump handle caustic soda?

Yes. Hawk offers a dedicated chemical pump for caustic soda within its NMT-ES Stainless Steel, NMT Chemical and NHDP Chemical series. These pumps use materials, AISI 316L stainless steel or EcoBrass® and special seals compatible with the alkalinity of sodium hydroxide solutions. Pressure ratings reach 200 bar and temperatures up to 85 °C.

What is the difference between a standard pump and a chemical resistant pump?

A standard pump has a brass head and standard steel valves, suitable for clean water. A chemical resistant pump uses special materials for every wetted component — AISI 316L stainless steel, EcoBrass®, nickel-plating, ceramic pistons, fluoropolymer seals — chosen specifically for the fluid being handled.

Can chemical resistant pumps work with demineralized or osmotic water?

Yes. Demineralized and osmotic water are chemically aggressive because they dissolve ions from unprotected metal surfaces. The Hawk NMT Chemical series, with EcoBrass® head and special seals, is specifically engineered for these applications, reaching 200 bar and flow rates up to 21 l/min.

What materials are best for pumps handling aggressive liquids?

The most reliable choices are AISI 316L stainless steel (resistant to chlorides and most acids), EcoBrass® (non-ferrous, ideal for demineralized water and mild solvents), technical ceramics for the pistons, and special elastomers (Viton®, EPDM, PTFE) for the seals. The exact combination depends on the chemical being pumped.

Are Hawk chemical pumps suitable for the food industry?

Yes. The NMT-HT (high temperature, 150 bar, up to 85 °C) and NMT-ES Stainless Steel (200 bar, up to 85 °C, AISI 316L) series are widely used for food industry sanitation, CIP cycles and washing applications with detergents and hot water. For specific configurations, contact the Hawk Pumps team.