Pump material selection covers every wetted component, not just the casing. Getting one component wrong such as a seal face, a gasket or an O-ring, can cause a failure just as fast as choosing the wrong casing alloy. Chemical compatibility depends on the exact chemical, concentration, temperature, contaminants and exposure time, so pH alone or a generic compatibility chart cannot confirm a material is suitable.
Every wetted component needs a decision
Material selection is often treated as a single choice, when it actually covers a list of separate components, each with its own duty:
- Casing and covers
- Impeller, rotor or pumping elements
- Shaft and sleeves
- Mechanical seal faces and secondary seals
- Diaphragms, hoses and tubes
- Valve balls, seats and springs
- Bushes, wear plates and liners
- Gaskets and O-rings
- Fasteners exposed to the fluid
- Flush, barrier or quench-system materials
Matching material properties to the actual duty
| Failure mode | What it means for material choice |
|---|---|
| Corrosion | Chemical attack on metals; needs a material rated for the specific chemical, concentration and temperature |
| Abrasion | Wear from solids; needs a hard or wear-resistant material, which may not also resist corrosion |
| Erosion-corrosion | Combined abrasive and chemical attack; often needs a different material than either alone |
| Swelling or softening | Common in elastomers exposed to certain chemicals; can occur without visible metal corrosion |
| Permeation | Some chemicals pass through elastomers over time, especially at higher temperature |
| Stress cracking | Certain plastics and elastomers crack under combined chemical exposure and mechanical stress |
Metals, elastomers and plastics behave differently
A hard, corrosion-resistant metal is not automatically the safest choice everywhere on the pump. Elastomers and plastics fail through different mechanisms — swelling, permeation and stress cracking rather than corrosion — and can degrade without any visible sign until the component leaks or fails suddenly.
Two materials that both “resist” the same chemical on a general compatibility chart can behave very differently once concentration, temperature or mechanical stress are added. A chart entry showing “good” resistance at room temperature says nothing about performance at an elevated process temperature.
Containment and sealing considerations
Material choice does not stop at corrosion and wear resistance. Hazardous, toxic, flammable, sterile or high-value fluids may require a specific sealing arrangement; double mechanical seals, leakage monitoring, containment shrouds or sealless designs, on top of the base material selection. The sealing arrangement and the material selection need to be reviewed together, since a seal flush or barrier fluid introduces its own compatibility requirements.
Practical checks before confirming a material selection
- Confirm the exact chemical name, concentration, temperature and any contaminants for every wetted component, not just the casing.
- Get current compatibility information directly from the manufacturer of each wetted component.
- Check compatibility at the maximum expected temperature and concentration, not just normal operating conditions.
- Confirm whether abrasion, corrosion or both are present, and select a material suited to the actual combination.
- Review containment and sealing requirements alongside material selection, not as a separate step.
- Confirm the final material combination against the complete fluid composition before ordering.
How to Select Pump Materials FAQs
Is a generic chemical compatibility chart enough to select materials?
No. Compatibility charts are a screening tool. They typically do not capture the exact concentration, temperature, contaminants and exposure time of the actual application. Confirm the final selection with current information from the manufacturer of each wetted component.
Can one material be used for the entire pump?
Sometimes, but not always. Different components face different failure modes such as corrosion, abrasion, permeation, stress cracking and the best material for one component is not automatically correct for another, particularly between metal and elastomer parts.
Why do pumps fail even with “compatible” materials?
Compatibility is often confirmed only for the base material against the primary chemical, while trace contaminants, cleaning chemicals, mixed process streams or combined mechanical and chemical stress go unchecked. Confirm compatibility for the complete process condition, not just the nominal chemical.
This article explains general principles for pump material selection. It does not replace manufacturer-confirmed compatibility data or a materials specialist’s review, particularly for hazardous, toxic or high-value fluids.
Part of the pump selection guide. See also How Solids Affect Pump Selection, How Viscosity Affects Pump Selection and Why Oversizing Pumps Causes Problems.
About The Pump Expert
The Pump Expert provides independent, practical education for pump users, engineers and maintenance teams. TPE explains how pumps and pump systems behave so readers can make better technical decisions without supplier bias.
Last Updated on July 30, 2026 by TPE