Industrial Coating

Here, we’ll describe the benefits and tradeoffs of four of the most common generic coating types: Epoxies, polyurethanes, and zinc-rich primers, providing examples of how each might be used in a total coating system.

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Epoxies

Epoxy coatings are typically comprised of an epoxy base and a curing agent. A wide variety of coating properties can be achieved by manipulating either of these components: Epoxy polyamide coatings offer great moisture resistance, epoxy mastic coatings offer exceptional film thickness and phenolic epoxy coatings offer good chemical resistance. And due to this versatility, you’ll find epoxies used as a primer, intermediate coat or even a topcoat depending on the needs of the application.

The most notable limitation of the epoxy family of coatings is their poor performance in sunlight — which is why epoxies are most often used in interior or submerged industrial applications. You might find epoxies protecting steel inside a nuclear power plant or submerged in a waste water treatment facility.

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Advantages

• Abrasion resistant

• Chemical resistant

• Good performance when submerged

• Can easily build film thickness for enhanced abrasion resistance

• Can be formulated to exhibit a wide variety of favorable coating properties

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Disadvantages

• Chalks when exposed to UV light

• Low flexibility

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Polyurethanes

Polyurethane coatings are widely used —often as a topcoat— in applications where durability and abrasion resistance are key considerations. Polyurethanes generally fall into two categories: Aliphatic and aromatic. Aliphatic polyurethanes provide excellent color retention and perform well in sunlight, making them well-suited to exterior environments. Aromatic polyurethanes, on the other hand, better lend themselves to submerged environments — they’ll chalk and weather when exposed to sunlight.

Most often, polyurethanes are chosen as the topcoat of a total protective coating system. For example, polyurethane might be applied as a topcoat above a zinc-rich primer and epoxy intermediate coat on a highway bridge. Or even as a topcoat on the concrete walls and floors of a nuclear power plant. Other possible applications include the topside of ships, the exterior of waste water treatment facilities or on locks and dams. Basically, polyurethanes are versatile enough to be formulated to handle a wide variety of service environments.

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Advantages

• Abrasion resistant

• High gloss and color retention

• Aliphatic polyurethanes perform well against weathering and UV light

• Aromatics perform well when submerged

• Low VOC formulations available

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Disadvantages

• Contains isocyanate (-NCO) ,a harmful carcinogen

• Skilled workers and protective equipment are necessary for application

• Higher priced than epoxies

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Selecting a coating system for your application: Weighing price and performance

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Industrial coating systems provide steel structures with long-term protection against their environment. To do this, the coating system must be well-equipped to handle the environmental conditions of its environment, whether that’s heat, sunlight, contact with chemicals or constant abrasions.

The prevailing service environment —along with factors such as cost, accessibility of the asset, expected labor costs, desired service life of the coating system— will dictate which coating system is best-suited for your application.