What Is Elastomeric Coating and How Does It Work?

The elastomeric coating process consists of applying a thin layer of elastomer directly onto a finished rubber part, adding a second material system on top of the base compound rather than replacing it. The result is a part with two engineered layers working together: the substrate handling structural and mechanical demands, and the coating handling whatever the surface environment throws at it.

How Elastomeric Coating Works

An elastomer is a polymer that exhibits viscoelasticity, meaning it deforms under pressure like a viscous fluid and recovers its shape like an elastic solid. That dual behavior is what lets a thin coating layer flex with the substrate underneath it instead of cracking or delaminating as the part moves, compresses, or cycles through temperature changes.

Moldtech applies the coating as a bonded layer over the base rubber part, not a sprayed-on or dipped finish sitting loosely on the surface. The bond between coating and substrate must hold through the same flex cycles, pressure, and thermal swings the part sees in service, or the coating separates and the base material is left exposed to whatever the coating was supposed to block.

Why Add an Elastomeric Coating?

A base compound is selected for mechanical performance: durometer, tensile strength, compression set, flex life. It isn’t always the best material for the surface conditions the part will face. An elastomeric coating layer lets you address that mismatch without redesigning the part around a single compromise compound.

Coating a finished part adds:

• Improved strength and isolation characteristics at the surface, without changing the mechanical properties of the base material
• Additional chemical and environmental resistance where the substrate alone would degrade under exposure
• Increased temperature capability beyond what the base compound can handle on its own
• Waterproofing at the surface layer, relevant for parts exposed to standing water, humidity, or washdown environments

This makes elastomeric coating a practical option when a part’s bulk properties and its surface exposure requirements pull in different directions, rather than forcing a single elastomer to do both jobs at once.

HNBR vs. FKM Elastomeric Coatings

Moldtech applies elastomeric coatings using two primary elastomer rubber systems, HNBR and FKM, each suited to a different exposure profile.

HNBR is the choice when a coated part needs to withstand higher temperatures than standard NBR allows while maintaining resistance to mineral oils, glycol coolants, hot water, and ozone.

FKM is the choice when the part needs broad resistance to fuels, petroleum-based oils and greases, and general media exposure over a long service life, along with strong resistance to ozone and aging.

Advanced Elastomer Systems: Coating Plus Substrate

Treating the coating and the base compound as one engineered system, rather than two independent material decisions, is what separates advanced elastomer systems from a simple surface treatment. The substrate is specified for the mechanical load path. The coating is specified for the surface exposure. Getting the combination right means neither material is being asked to do a job it wasn’t selected for.

This is also where a vertically integrated manufacturing process matters. Moldtech handles compounding, molding, and coating application within the same facility, so the coating step is engineered against the base part’s actual properties rather than applied as a disconnected finishing process.

For elastomeric coating projects, contact Moldtech’s engineering team to discuss substrate compatibility, exposure conditions, and coating selection, or visit the Elastomeric Coating capabilities page to review Moldtech’s coating application services.

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