Chemical Compatibility Chart: How to Select Compatible Materials
Selecting materials for fluid handling equipment involves more than matching a pump or valve to the required flow and pressure. Every wetted component is exposed to the process fluid. Those materials do not all respond the same way.
That is why engineers use a chemical compatibility chart during equipment selection. It helps compare material options before equipment is specified, purchased, or repaired. It can also help troubleshoot premature failures involving seals, hoses, valves, or piping.
What is a Chemical Compatibility Chart?
A chemical compatibility chart compares published compatibility data for metals, plastics, elastomers, and other engineering materials exposed to specific fluids.
You may also see these resources referred to as a chemical resistance chart, material compatibility chart, or chemical compatibility guide.
Most charts include materials such as:
- Stainless steel
- Carbon steel
- Cast iron
- PVC
- CPVC
- Polypropylene
- PTFE
- EPDM
- Viton®
- Buna-N
- Neoprene
The rating tells you how the material has performed when exposed to a specific chemical under defined conditions. It does not automatically mean the material is suitable for every application.
Things That Can Change a Compatibility Rating
Compatibility charts are based on published testing and field experience, but they cannot represent every operating condition.
Temperature and Concentration
Temperature is one of the first things to review when evaluating material compatibility.
A material that performs well at room temperature may soften, swell, harden, or corrode more quickly as process temperatures increase. Steam cleaning, hot CIP cycles, and seasonal operating changes can also influence long-term performance.
Chemical concentration deserves the same attention. For many chemicals, dilute and concentrated solutions have different compatibility ratings. Always compare your actual process conditions with the data used to develop the chart.
Process Conditions
Compatibility charts don’t account for how a component is used in service. For example, ask yourself:
- Is the component continuously exposed or only during cleaning?
- Is it a static gasket or a rotating shaft seal?
- Will abrasive solids pass through the equipment?
- Will the system cycle between hot and cold temperatures?
Those questions often influence service life as much as chemical compatibility.
Mixed Process Fluids
Published compatibility data is commonly based on individual chemicals.
Industrial process fluids are often mixtures containing additives, corrosion inhibitors, suspended solids, cleaning chemicals, or proprietary ingredients. If the process fluid is a blend, use the compatibility chart as an initial screening tool, then review the application with the equipment manufacturer or supplier.
How Engineers Use Chemical Compatibility Charts
A compatibility chart rarely identifies a single “correct” material. Instead, it helps eliminate materials that are likely to fail.
An engineer may begin with several possible materials for a pump casing, mechanical seal, O-rings, and hose assembly. The remaining candidates are then compared against pressure, temperature, mechanical strength, wear resistance, maintenance requirements, and cost.
One point that is easy to overlook is that every material in contact with the process fluid should be reviewed. For example, a stainless steel pump casing may be fully compatible with the process fluid while the elastomer selected for the mechanical seal or O-rings is not. In many applications, seals fail long before the metal components show signs of chemical attack.
Common Material Families Found on Compatibility Charts
Metals
Stainless steel, carbon steel, cast iron, and specialty alloys appear on nearly every chemical compatibility chart.
These materials are commonly selected for structural strength and pressure capability, but corrosion resistance varies by alloy. A compatibility rating for 316 stainless steel should not automatically be applied to every stainless steel component.
Plastics
PVC, CPVC, polypropylene, PTFE, and other engineered plastics are widely used in chemical processing because many resist corrosion better than traditional metals.
Each material has operating limits, though. Some perform well in aggressive chemical service but have lower pressure or temperature limits than metal components.
Elastomers
Elastomers often determine how long equipment remains leak-free.
Materials such as EPDM, Viton®, Buna-N, and neoprene are commonly used for O-rings, gaskets, diaphragms, and seals. These components may swell, shrink, harden, or lose elasticity after prolonged chemical exposure, even when the surrounding metal parts remain in good condition.
When reviewing a material compatibility chart, don’t stop after confirming the housing material. Review every seal and gasket that contacts the process fluid.
When Published Compatibility Data isn’t Enough
Chemical compatibility charts are valuable reference tools, but they have limits. Take a closer look at the application if:
- Process fluids contain multiple chemicals
- Operating temperatures exceed published test conditions
- Chemical concentrations differ from the published data
- Abrasive solids are present
- Exposure is continuous for long periods
- The application involves high pressure or specialized equipment
Material selection becomes more complex as operating conditions move farther away from standard laboratory testing.
Where to Find Chemical Compatibility Charts
Many equipment manufacturers publish compatibility information for their own products. Independent resources are also available.
One of the most widely used references is the Cole-Parmer Chemical Compatibility Database. Although some users refer to it as a chemical compatibility calculator, it functions as a searchable database that compares compatibility ratings for metals, plastics, elastomers, and other materials.
No single chart should replace manufacturer recommendations or application engineering. Compatibility charts are intended to narrow material choices, not approve an equipment design.
Need Help Selecting Compatible Materials?
A chemical compatibility chart is one part of equipment selection. Operating conditions, process requirements, and equipment design also influence which materials are appropriate for a given application. If you’re evaluating fluid handling equipment, DXP’s application specialists can help review material compatibility and recommend products for your application.
