Choosing Chemical-Resistant Mount Materials For Splash-Prone Equipment

Scope and caution: The material guidance below is intended for screening and specification development. Chemical resistance depends on the specific chemical, concentration, temperature, exposure duration, mechanical stress, and grade or formulation. Final selection should be confirmed with material suppliers and site-specific compatibility testing. No material table can replace an exposure-specific test report.

Start With an Exposure and Performance Definition

Splash-prone equipment failures are often caused not by a single aggressive chemical, but by a combination of trapped liquid, crevice geometry, galvanic coupling, temperature cycling, and cleaning chemistry. Before comparing materials, define the actual service conditions.

A useful first step is to build a simple exposure matrix for each mounting location. The matrix becomes the basis for supplier questions, compatibility testing, and the final documented selection basis.

Environmental Factors That Drive Material Choice

Temperature range

Elastomers do not have a single universal temperature rating. Their stiffness, damping, compression set, and chemical resistance change with temperature and formulation. A material that performs well at room temperature may harden, soften, creep, or degrade at process temperature.

For vibration isolators, verify:

• Continuous service temperature, not only short-term peak temperature.
• Low-temperature behavior if equipment is started cold or exposed to winter conditions.
• Dynamic stiffness and damping at the actual operating temperature.
• Compression set under sustained load.
• Aging and fatigue effects over the expected service life.

Salt spray, humidity, and condensation

Salt spray and humidity primarily affect metallic components, fasteners, coatings, and interfaces. Stainless steel selection matters, but so do crevices, weld quality, passivation, and mixed-metal contact. Condensation can be more damaging than visible splash because it wets hidden surfaces and dilutes or concentrates chemicals as it evaporates.

Chemical contact

Chemical resistance charts are screening tools, not approvals. For each candidate material, document:

• Chemical name and concentration.
• Temperature during exposure.
• Duration and frequency.
• Whether the exposure is splash, vapor, condensation, or immersion.
• Mechanical stress during exposure.
• Cleaning chemicals and rinse water.
• Mixtures or process changes that could alter chemistry.

For critical applications, test coupons of the actual material and finish under representative conditions. Include post-test checks for mass change, volume swell, hardness change, tensile or elongation retention, compression set, coating adhesion, and corrosion morphology.

Material and Surface Options: Screening Guide

The following tables are indicative only. Formulations vary by supplier, and compatibility must be confirmed for the exact grade and exposure conditions.

Elastomer screening

Metallic and coating screening

Practical rule: Choose the elastomer for chemical compatibility and dynamic performance, then choose the metal and coating system for corrosion resistance and mechanical strength. Do not assume that a corrosion-resistant metal solves an elastomer compatibility problem.

Stainless Grade, Coatings, and Mixed-Metal Compatibility

Stainless grade selection

For splash-prone industrial equipment:

• 304 stainless may be adequate in mild indoor environments with low chloride exposure.
• 316 or 316L stainless is generally preferred where chlorides, coastal air, or aggressive washdown chemicals are present.
• 316L is often specified for welded components to reduce sensitization risk.
• Passivation should be specified and verified. A clean, passive surface is part of the corrosion-resistance system.

316 stainless is not a universal solution. It can suffer crevice corrosion and chloride stress-corrosion cracking under certain conditions, especially in warm, concentrated chloride environments or tight crevices. Evaluate gaskets, washers, threads, and trapped interfaces as carefully as the main body.

Coatings

Coatings can extend base-metal life, but they introduce failure modes:

• Poor adhesion can lead to blistering and undercutting.
• Damaged edges and bolt holes become initiation sites.
• A coating that is chemically compatible with the process fluid may still fail under cleaning chemicals.
• Coating flexibility must match the thermal and mechanical movement of the part.

Specify coating thickness, adhesion test method, cure requirements, and repair procedure for damaged areas.

Mixed-metal compatibility

Galvanic corrosion is a common hidden failure in splash-prone equipment. It occurs when dissimilar metals are coupled in the presence of an electrolyte. Risk increases with:

• Salt spray or conductive washdown water.
• Trapped moisture in crevices.
• Large cathode-to-anode area ratios.
• Threaded fasteners and small washers coupled to larger structural components.

Mitigation options include:

• Use compatible or identical fastener and base materials where practical.
• Use isolating washers, bushings, or sleeves to break electrical contact.
• Seal crevices or design them out.
• Specify compatible anti-seize or thread lubricant.
• Avoid small anodic fasteners coupled to large cathodic structures.
• Document the galvanic pair in the assembly drawing and inspection plan.

Stiffness, Damping, Corrosion, and Service Life

Stiffness and damping

Vibration isolation performance depends on the dynamic stiffness and damping of the mounted system, not only the static load rating. A material that is chemically resistant but too stiff may transmit vibration into the equipment frame. A material that is too soft may provide good isolation at low frequency but suffer excessive deflection, creep, or instability under shock loads.

For each application, define:

• Equipment mass and center of gravity.
• Forcing frequencies and expected harmonics.
• Allowable vibration transmission.
• Shock and startup loads.
• Static deflection limits.
• Available installation height.
• Required horizontal stability.

Where practical, specify dynamic stiffness and damping at the operating temperature and frequency range. A suppliers static load curve alone is not sufficient for critical equipment.

Corrosion and service life

Service life is influenced by:

• Chemical concentration and temperature.
• Continuous wetting versus intermittent splash.
• Crevice geometry and drainage.
• Mechanical stress and cyclic loading.
• UV and ozone exposure.
• Cleaning frequency and cleaning chemistry.
• Compression set and creep.

A conservative selection basis should include historical data from similar installations, supplier aging data, and post-test inspection results. Salt spray testing can compare finishes and detect gross weaknesses, but it does not directly predict service life in a specific chemical environment.

Drainage, Cleaning Access, Fasteners, and Interface Details

Drainage

Splash-prone mounts should not create liquid traps. Design and installation should:

• Avoid upward-facing cavities and blind holes.
• Provide drain holes or open channels where practical.
• Slope mounting surfaces so liquid can run away from the isolator.
• Avoid tight crevices between elastomer, washer, and metal.
• Consider that drained liquid must be directed away from other equipment and walkways.
• Inspect for accumulation after washdown, not only during normal operation.

Cleaning access

Cleaning and inspection access should be designed in, not added later:

• Use smooth, non-porous surfaces where possible.
• Avoid absorbent gaskets and open-cell materials.
• Provide wrench clearance and removal space.
• Use removable or replaceable components where frequent inspection is expected.
• Define a cleaning procedure compatible with the selected elastomer and coating.

Fasteners and interfaces

Fasteners are often the first components to corrode. Specify:

• Corrosion-resistant fasteners appropriate to the environment.
• Compatible washer and bushing materials.
• Correct torque and tightening sequence.
• Anti-seize or lubricant compatibility with process chemicals.
• Thread sealing or drainage where liquid can enter blind holes.
• Interface flatness and contact area to avoid stress concentrations.

The mating surface between the isolator and the equipment should be reviewed for both mechanical and galvanic compatibility. A small incompatible washer can initiate failure of a well-selected mount.

Environmental Test Conditions and Post-Test Inspection Evidence

A defensible test plan should mimic the actual failure mode, not only a standard laboratory condition. A practical validation plan should include:

1. Material coupons of the exact elastomer, coating, and metal finish.
2. Exposure conditions matching chemical, concentration, temperature, and duration.
3. Cyclic wetting and drying where splash and drainage are expected.
4. Post-test inspection for mass change, swelling, hardness change, cracking, blistering, coating adhesion, pitting, crevice corrosion, and fastener condition.
5. Dynamic performance check after exposure where isolation performance is critical.
6. Photographic records and a signed test report.

Post-test inspection should be documented before the material is approved for the bill of materials.

Documenting the Selection Basis and Procurement Specification

A documented selection basis protects engineering, procurement, and maintenance teams. It should be concise but specific enough to support an audit or a future replacement decision.

A procurement specification can then use clear, testable language:

Mount elastomer shall be [specified grade] compatible with [chemical, concentration, temperature, exposure mode]. Metal components shall be [304/316L] stainless steel, passivated in accordance with ASTM A967. Fasteners shall be [material] with isolating washers where required to prevent galvanic coupling. The mount shall provide drainage from the mounting interface and allow visual inspection without removal of adjacent equipment. Supplier shall provide material certificates, chemical compatibility statement, and test reports for the specified exposure conditions. Any material or formulation change requires written notification and engineering approval.

Procurement teams should also review supplier reliability, lead time, minimum order quantity, certificate availability, change-control process, and replacement-part availability. The lowest initial price can be misleading if the mount fails early or requires a long-lead replacement.

Common Failure Modes and Design Responses

These examples are conceptual and must be validated for the actual chemicals, concentrations, temperatures, and equipment dynamics.

Scenario A: Food or beverage washdown frame

Conditions: Daily alkaline foam cleaning, occasional chlorinated sanitizer, wet environment, stainless frame.

Screening direction: EPDM may be considered for alkaline washdown compatibility, with 316L stainless hardware and passivation. Chlorinated cleaners and warm crevices require specific confirmation because stainless steel is not immune to chloride attack. Drainage and smooth surfaces are critical.

Scenario B: Machine tool coolant and oil mist

Conditions: Continuous oil mist, coolant splash, metal chips, moderate temperature.

Screening direction: NBR or FKM may be considered for oil resistance, depending on coolant chemistry and temperature. Polyurethane may be considered where abrasion resistance is important, but its resistance to hot water and alkaline cleaners must be checked. Fasteners and washers should resist the coolant and cleaning chemicals.

Scenario C: Coastal pump skid

Conditions: Salt spray, humidity, occasional freshwater rinse, outdoor exposure.

Screening direction: 316L stainless hardware and passivated surfaces are generally preferred over 304. Elastomer selection depends on any oil or chemical exposure from the pump. Mixed-metal interfaces, threaded holes, and crevices should be reviewed for galvanic and crevice corrosion.

Conclusion

Selecting chemical-resistant mount materials for splash-prone equipment is an evidence-based engineering decision, not a catalogue lookup. The most reliable approach is to define the exposure matrix, screen materials against the actual chemicals and temperatures, evaluate stiffness and damping at operating conditions, design for drainage and inspection, and validate the final system with representative testing.

For OEM engineers and technical purchasing teams, the strongest procurement position is a documented selection basis: specific material grades, test evidence, installation requirements, fastener compatibility, and change-control expectations. This reduces the risk of premature failure, unplanned downtime, and costly replacement in demanding industrial environments.

Selected Standards and References

The following standards are useful references for screening and specification development. Verify current editions and applicable clauses for the specific project.

• ASTM B117 Operating Salt Spray (Fog) Apparatus.
• ISO 9227 Corrosion tests in artificial atmospheres: salt spray tests.
• ASTM D471 Rubber Property: Effect of Liquids.
• ISO 1817 Rubber, vulcanized or thermoplastic: determination of the effect of liquids.
• ASTM D543 Resistance of Plastics to Chemical Reagents.
• ISO 175 Plastics: methods of test for the determination of the effects of immersion in liquid chemicals.
• ASTM G48 Pitting and crevice corrosion resistance of stainless steels and related alloys by use of ferric chloride solution.
• ASTM A967 Chemical passivation treatments for stainless steel parts.
• Standard practice for cleaning, descaling, and passivation of stainless steel parts.