A Simple, Robust Framework for Specifying Coatings in Water Treatment Systems

By: Induron Protective Coatings

Across the United States, municipal water and wastewater systems are facing unprecedented pressures. Aging infrastructure, tightening regulations, and financial shortfalls are converging to create a daunting challenge for operators and engineers. According to the American Society of Civil Engineers’ most recent “Report Card,” water and wastewater utilities collectively face hundreds of billions of dollars in unmet capital needs over the coming decades. At the same time, the infrastructure we do have—pipes, tanks, clarifiers, aeration basins, and countless other assets—is deteriorating under the relentless forces of corrosion and erosion.

Corrosion alone is estimated to cost U.S. utilities tens of billions of dollars annually, and concrete deterioration, though less studied, may ultimately exceed those costs due to the vast surface areas involved in treatment plants. Despite the enormity of the problem, there remains no universal, industry-wide standard for preventing corrosion across all the varied assets in water and wastewater systems.

Induron’s recent white paper, A Simple, Robust and Exhaustive Scheme for Specifying Coatings in Water Treatment Systems, seeks to fill that gap by proposing a practical, chemistry-based framework for evaluating corrosive environments and selecting protective coatings.

The Specification Problem

Unlike steel potable water tanks, which are addressed in detail by standards such as AWWA D102, many water and wastewater assets have no consistent guidance for coatings. Operators are left to rely on a patchwork of manufacturer specifications, contractor experience, and case-by-case engineering judgment.

This leads to two common problems:

1. Over-specification, where an asset is coated with an unnecessarily expensive, high-performance lining, driving up project costs.
2. Under-specification, where a light-duty coating is chosen for a highly corrosive environment, leading to premature failure, costly downtime, and safety risks.

The sheer variety of asset types—clarifiers, tanks, channels, pipes, concrete basins, and more—combined with the diversity of water chemistries, makes standardization a difficult task. For example, even within a single clarifier, operators may encounter immersed concrete, atmospheric concrete, galvanized walkways, steel rakes, ductile iron piping, and expansion joints. Each material interacts differently with water chemistry and requires different surface preparation and coatings.

Corrosion Chemistry: Why Water Matters Most

At the heart of the problem is water itself. Because of its unique chemical properties, water acts as the primary driver of corrosion. Its polarity allows it to carry ions, dissolve gases, and catalyze chemical reactions that degrade metals and concrete alike.

For metals like iron and steel, pH plays a crucial role. Corrosion accelerates in acidic environments (low pH) but also varies based on the presence of oxidizing or reducing agents. Zinc, used in galvanization, corrodes differently—being vulnerable to both high and low pH extremes.

Concrete, often thought of as inert, is equally susceptible. Low pH can lead to rebar corrosion, carbonation, or microbial-induced corrosion, while high pH can trigger destructive alkali-aggregate reactions. All of these processes depend on the same four elements of corrosion: an anode, a cathode, an electrolyte, and a conductive pathway.

This makes the measurement of pH and the identification of oxidizing or reducing agents central to predicting how quickly a given substrate will degrade.

The BOAR Model: A Practical Solution

To bring clarity to this complexity, the white paper introduces the BOAR model, a simple framework based on water chemistry. BOAR stands for Basic, Oxidizing, Acidic, and Reducing—the four broad categories of corrosive environments.

By plotting an environment’s pH (acidic or basic) against its electrochemical potential (oxidizing or reducing), asset owners can quickly classify the corrosive conditions at play.

For example:

●     Chlorine contact chambers fall into the basic and oxidizing quadrant due to the presence of hypochlorite or ozone.

●     Potable water storage tanks are usually neutral to slightly basic, sometimes with mild oxidizing stresses from chlorine.

●     Wastewater basins affected by microbial activity may generate sulfuric acid, creating a highly acidic and oxidative environment.

This simple categorization avoids the need to create an asset-by-asset specification. Instead, the focus shifts to service environment chemistry—a more universal, transferable approach.

Matching Coatings to Conditions

Once corrosive conditions are categorized, coating selection becomes much clearer. While there are countless formulations on the market, most water infrastructure coatings fall into three main resin families:

1. Epoxies and Novolacs: Highly resistant to acids, bases, and oxidizers. Versatile and widely used in immersion service.
2. Polyurethanes and Polyureas: Excellent against bases and oxidizers, with flexible, high-build applications. Less effective in acidic conditions.
3. Vinyl Esters and Polyesters: Exceptional acid resistance, but limited against bases and oxidizers.

By aligning these resin properties with BOAR’s four categories, coatings specifiers can develop rational, site-specific coating strategies without needing exhaustive asset-by-asset rules. Importantly, all three resin families also meet NSF/ANSI 600 standards for potable water applications, ensuring regulatory compliance.

Moving Toward a Universal Specification

The long-term vision is for the industry to adopt a universal specification standard based not on asset type, but on water chemistry. Such a standard would:

●     Provide consistent guidance across utilities.

●     Reduce over- and under-specification.

●     Extend asset life while minimizing costs.

●     Enable operators to make informed decisions with readily available water quality data.

For example, instead of specifying “coat clarifier walls with X system,” a universal standard might say: “For immersion services with pH ≥ 7 and oxidizing conditions (chlorine or ozone present), apply a 100% solids epoxy lining at 30–40 mils.”

This chemistry-first approach is both more exhaustive and more adaptable than current practices, which often rely on naming assets rather than defining environments.

The Path Forward

While the BOAR model is not without its limitations—it simplifies complex electrochemical processes and does not fully account for factors like ionic strength—it provides a practical, scalable framework that can be readily applied in the field.

The next step will require collaboration among coating manufacturers, engineers, operators, and professional organizations like AWWA, AMPP, and WEFTEC. Together, the industry can create a more unified specification system that ensures resilience and cost-effectiveness for decades to come.

Conclusion

Water utilities are under pressure to do more with less. Corrosion remains one of the greatest threats to asset integrity, yet current standards do not adequately address the diversity of materials and environments in treatment plants.

By shifting focus from asset type to water chemistry, the BOAR model offers a simple, robust, and universal scheme for specifying coatings. With broader industry adoption, this approach has the potential to save utilities millions of dollars, reduce downtime, and extend the service life of critical infrastructure.

“The BOAR model isn’t about reinventing coatings,” said Induron’s Technical Director William Seawell. “it’s about simplifying the decision-making process. By understanding the chemistry of your environment, you can make smarter choices that extend the life of your assets and protect public resources.”

In the end, a simple change of focus from asset type to water chemistry and a small amount of low-cost analytical work may be the most powerful tools treatment plant operators have in the fight against corrosion.