When to Coat—and When Not To: A Technical Guide for Rotating Equipment Owners

To coat, or not to coat? That’s the question many rotating equipment owners face when balancing long-term reliability with maintenance budgets. Protective coatings have been used for decades to shield pumps, compressors, turbines, and agitators from corrosion, erosion, and fouling—but the decision to apply them isn’t always straightforward. Factors such as process media, operating environment, velocity, and expected service life must all be weighed carefully.

At its core, the argument for coatings comes down to extending the life of critical assets, improving operating efficiency, and reducing maintenance frequency. But coatings also carry limitations, and in some cases, alternative technologies such as composites may provide better long-term performance.

Advantages of Coatings

Extended Service Life and Reliability

Capital equipment is one of the most significant investments a facility makes, and coatings can serve as a protective insurance policy. According to data from the World Corrosion Organization, corrosion costs industries worldwide more than $2.5 trillion annually—about 3–4% of global GDP. Even modest protection against this damage can yield substantial financial savings.

In practice, coatings can extend the mean time between failures (MTBF) for pumps and compressors by several years, particularly in aggressive chemical or abrasive environments. For example, field studies in petrochemical plants have shown that coated pump impellers exposed to high-chloride brines experienced 40–60% longer service intervals compared to uncoated components.

Efficiency and Energy Savings

Coatings not only protect but also improve hydraulic efficiency. Research indicates that even a 2% efficiency gain in a pump system can recover coating costs in less than a year due to reduced energy consumption. For a 1,000-horsepower motor, this could equate to tens of thousands of dollars in annual electricity savings. Smooth, low-friction coating surfaces help minimize turbulence, improving flow and reducing drag.

Versatility Across Applications

Rotating equipment often operates in environments where corrosion, cavitation, scaling, and fouling are unavoidable. Coatings mitigate these risks by:
– Reducing friction and wear in abrasive services.
– Providing chemical resistance against caustic or acidic fluids.
– Improving resistance to cleaning chemicals and solvents.
– Enhancing start-up reliability after extended shutdowns.

Types of Coatings

Coatings fall into two main categories:

• Organic Coatings (thermoset polymers, elastomers, epoxy resins): Cost-effective, widely used, and relatively easy to apply. Best suited for mild-to-moderate chemical environments and applications with lower turbulence.

• Inorganic Coatings (ceramics, glass linings, metallic overlays, silicone-based): More durable, offering excellent resistance to high wear and highly corrosive conditions. However, they are more expensive and can be difficult to apply in the field.

Selecting between these requires understanding whether your dominant service challenge is mechanical (erosion/cavitation), chemical (corrosion), or thermal (heat cycling).

Disadvantages of Coatings

Degradation Over Time

The moment a coating is applied, it begins a natural degradation process. Thermal cycling, vibration, and abrasion eventually create pinholes or delamination. Once corrosive process media penetrates beneath the coating, metal loss accelerates—sometimes faster than if the surface had never been coated at all.

Performance Trade-Offs

In some instances, coatings reduce equipment performance. For example, if coating thickness obstructs flow passages or changes hydraulic clearances, pumps can be forced off their best efficiency point (BEP). This can shorten bearing life, increase vibration, and ultimately reduce overall equipment lifespan.

Limitations in High-Velocity Service

Coatings are generally not recommended for high-velocity or slurry applications, where abrasive particles erode them quickly. In services such as crude oil transfer or mine dewatering, reapplication cycles can be so frequent that coatings become cost-prohibitive.

Structural Composite Components: An Alternative

When coatings cannot provide adequate protection, structural composites may be the next step. Unlike metals that require surface treatments, composites are inherently corrosion-resistant and are manufactured as solid pieces.

Key Benefits of Composites

– Corrosion Immunity: Since there’s no metallic substrate, corrosive fluids cannot undermine the material.
– Lightweight and Strong: Composite wear rings, bushings, and impellers reduce rotating mass, leading to significant energy savings.
– Elastic Recovery: While metals dent or yield under stress, composites often return to their original shape.
– Non-Conductive: Ideal for high-voltage applications where electrical isolation is critical.
– Durability: Resistant to pitting, scaling, and many forms of mechanical damage.

Protective coatings offer a practical, cost-effective way to extend the life and efficiency of rotating equipment, particularly in applications with moderate corrosion and wear. However, they are not a one-size-fits-all solution. For severe or highly erosive environments, coatings may degrade quickly and actually add cost over time. In those cases, upgrading to structural composites may provide a more permanent solution.

Ultimately, the choice between coatings, composites, or uncoated metals depends on process conditions, budget, and long-term asset management goals. The right strategy can reduce energy use, extend mean time between failures, and lower total lifecycle costs—allowing facilities to maximize the return on their rotating equipment.

Houston Dynamic brings decades of hands-on experience in rotating equipment repair, upgrades, and performance optimization. Our team has worked across industries—from petrochemical and refining to power generation—helping clients extend equipment life, improve efficiency, and reduce unplanned downtime. Whether you’re considering coatings, exploring composites, or facing a complex repair challenge, we combine engineering expertise with proven solutions to keep your assets running at peak performance. Partner with us for reliable results and a commitment to excellence in every project.