What Causes Premature Coating Failure? Key Factors in Harsh Water Environments

The Importance of Coating and Lining Systems for Water and Wastewater Assets

Water and wastewater treatment assets operate under some of the most punishing environmental conditions. Whether submerged in treated water, raw sewage or aggressive wastewater, infrastructure components must endure exposure to corrosive agents, constant humidity and intense microbial activity. Without an effective coating system in place, these elements can attack metal and concrete substrates, rapidly deteriorating equipment and structures.

Protective coatings and linings serve as a barrier, shielding surfaces from moisture ingress, chemical attack and mechanical damage. They preserve structural integrity, prevent contamination and extend asset life cycles—all while supporting operational efficiency.

With the right coating solution and proper application, utilities and industrial operators can reduce maintenance burdens, avoid unplanned outages and maintain compliance with stringent regulatory standards.

5 Factors That Impact Coating Integrity in Harsh Water Environments

Protective coatings in water and wastewater applications face numerous threats that can compromise their effectiveness over time. Understanding these environmental stressors is vital for specifying and applying the right coating system for the job.

1. Constant Immersion and Water Chemistry

Continuous immersion in both treated and untreated water subjects coatings to near-constant exposure to a wide variety of chemical compositions. Aggressive ions such as chlorides and sulfates, along with fluctuating pH levels, can weaken or break down protective barriers.

When coatings aren’t engineered for this level of exposure, the risk of blistering, delamination or film erosion increases significantly. Over time, even the smallest pinhole or breach in the film can serve as a pathway for water to reach the substrate and initiate corrosion beneath the surface.

2. Microbial Induced Corrosion (MIC)

Microorganisms, especially sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB), thrive in wastewater environments. The SRB produce hydrogen sulfide that the SOB metabolizes to sulfuric acid, which can rapidly corrode steel and concrete surfaces.

If coating and lining systems are not resistant to sulfuric acid, they can break down prematurely, compromising the asset’s longevity. MIC is notoriously difficult to detect until substantial damage has occurred, so resistant coatings are a necessity from the outset.

3. Salt and Chloride Contamination

In coastal regions or areas using deicing salts, airborne or splash-borne chlorides can infiltrate protective coatings. Even trace levels of chlorides can disrupt adhesion and lead to osmotic blistering, where water is drawn through the coating to salt crystals beneath. The result is accelerated underfilm corrosion and a dramatic drop in coating performance.

Chloride contamination is particularly insidious because it can be present even after seemingly thorough surface cleaning, further emphasizing the need for proper testing and remediation.

4. Temperature and Humidity Extremes

Extreme fluctuations in temperature and humidity can wreak havoc on coating systems during both application and service life.

High temperatures may cause coatings to cure too quickly or unevenly, while low temperatures can delay curing and reduce adhesion. Humid conditions introduce moisture during the application process, increasing the risk of pinholes, blisters or poor intercoat adhesion.

Over the long term, thermal expansion and contraction cycles can cause coatings to crack or lose flexibility, reducing their ability to protect.

5. Mechanical Stress and Erosion

Water treatment systems are dynamic environments. High-velocity flows, suspended solids and mechanical agitation all contribute to surface erosion. Components like pump housings, clarifier mechanisms and internal tank walls can suffer accelerated wear when not protected with an erosion-resistant coating.

Additionally, repeated contact from tools or maintenance equipment can chip or gouge coatings, creating failure points that spread over time.

Common Implications and Consequences of Coating Failure

The breakdown of a protective coating system in a water or wastewater environment is more than a cosmetic concern. It introduces serious operational, financial and compliance risks that can escalate quickly if not addressed.

Corrosion and Substrate Damage

Once the protective film is compromised, water and aggressive agents reach the substrate, initiating corrosion. For steel, this process leads to oxidation, pitting and, ultimately, structural failure. In concrete, chemical ingress can cause spalling or reinforcing steel corrosion.

The resulting damage compromises structural integrity and often requires costly repairs or full replacements.

Operational Downtime

Coating failures can lead to unplanned maintenance or complete system shutdowns. Whether the failure occurs in a clarifier, digester or filtration basin, repairs are typically time-consuming and disruptive.

Shutdowns delay treatment processes, reduce plant efficiency and increase labor and equipment costs. In some cases, backup systems may be insufficient, which risks service interruptions for end users.

Increased Maintenance Costs

Remediating coating failures is almost always more expensive than preventing them. Rework involves removing failed material, re-prepping surfaces and reapplying coatings—often under tight timelines. As failures multiply, the cost of inspections, recoating and structural repairs quickly escalates, straining already tight maintenance budgets.

What Does Premature Coating Failure Look Like?

Spotting the early signs of coating failure can help mitigate further damage. Coating deterioration is often visible to the trained eye and knowing what to look for makes timely intervention possible.

Blistering and Delamination

Blistering is often a result of moisture, solvents or contaminants trapped beneath the film. Delamination, on the other hand, can signal poor surface prep or incompatible layers. These issues appear as raised bubbles or flaking areas where the coating has separated from the surface.

Both symptoms allow corrosive agents to reach the substrate, creating a domino effect of degradation.

Rust and Discoloration

Rust spots, streaks or patches of discoloration are visual red flags that corrosion has breached the coating barrier. These areas often start small but can expand rapidly, especially in immersed or high-humidity environments. In metallic surfaces, rust may appear orange-brown, while on concrete, staining might indicate rebar corrosion which should be addressed immediately.

Discoloration can also be a sign of UV degradation or chemical attack, depending on the environment.

Cracking and Peeling

Cracks typically form due to thermal cycling, UV exposure or aging of the coating film. Once cracks appear, they allow moisture and chemicals to seep beneath the surface. Peeling often follows, as the bond between the coating and the substrate fails. These signs indicate a compromised system that needs immediate evaluation.

Erosion or Film Loss

Visible thinning or bare spots in a coating may result from abrasion, turbulent flow or chemical attack. These areas may feel rough to the touch or show uneven gloss. Over time, erosion reduces the protective thickness required to shield the substrate.

Without intervention, erosion or film loss can accelerate degradation and eventually lead to substrate failure.

6 Causes of Premature Coating Failure in Water and Wastewater Infrastructure

Premature coating failure is usually the result of a combination of factors—from poor surface prep to inadequate product selection—that compromise the performance of the coating system. These failures can arise during initial application, environmental exposure or routine service.

To prevent these failures, it’s critical to consider the most common causes, break down each contributing factor and understand how it leads to breakdowns in coating integrity.

1. Inadequate Surface Preparation

The foundation of any successful coating system is surface preparation.  Full-time inspection of the work by a qualified inspector is the best way to assure the job is completed correctly.

If the substrate isn’t properly cleaned and profiled, even the highest-performing coating will fail to adhere and perform as intended. Skipping steps, using incorrect cleaning agents, or rushing the preparation process often leads to insufficient adhesion and rapid coating breakdown.

Presence of Contaminants

Contaminants like oil, grease, dust and salt are among the most common causes of coating adhesion failure. These substances act as barriers between the substrate and the coating, preventing effective bonding. Even minute traces can result in localized failure, leading to blistering, pinholing or underfilm corrosion.

Ensuring surfaces are contaminant-free prior to coating is a non-negotiable step in any successful project.

Inadequate Roughness

Surface profile, or roughness, is crucial for mechanical bonding. A smooth substrate lacks the necessary texture to allow the coating to grip effectively. If the profile is too shallow, the coating may peel or delaminate over time.

Abrasive blasting to the correct standard helps create the surface anchor pattern that enhances long-term adhesion.

Chloride Contamination

Chloride (and other soluble salts) are notorious for causing osmotic blistering beneath coatings. These salts, often found in marine or coastal areas, attract moisture through the coating film, leading to subsurface pressure and film rupture. Even after cleaning, chlorides can remain embedded in the substrate unless properly tested and removed.

Salt testing kits and appropriate remediation techniques are essential tools in surface prep for chloride-prone environments.

2. Inadequate Coating Selection

Not every coating system is right for every application. Using a product that isn’t engineered for the specific environmental, chemical or mechanical conditions of the asset can lead to rapid deterioration.

Relying solely on cost or availability often results in coatings that simply can’t withstand the demands placed upon them. Instead, the selection process should involve a thorough evaluation of immersion conditions, temperature fluctuations, abrasion risks and chemical exposure.

Incompatibility

Todays modern high-performance coatings aren’t necessarily good-better-best.  Each system is specifically formulated for specific service conditions.  A coating may perform well in one setting but fail entirely in another. Immersion environments, for example, require coatings designed specifically for continuous water contact. Using a general-purpose paint or selecting a system not intended for wastewater conditions will result in rapid breakdown.

Compatibility with substrate materials, operating conditions and existing coatings must be verified before application.

Insufficient Resistance

If a coating lacks adequate resistance to the chemicals or environmental conditions it will face, it will degrade prematurely. This process can manifest as discoloration, softening, embrittlement or total loss of protective function.

Coatings exposed to acids, alkalis, solvents or UV light must have specific formulation properties to withstand those conditions. When coatings are pushed beyond their intended limits, failure is only a matter of time.

Formulation Issues

Even the right coating can fail if it’s poorly formulated. Issues such as improper resin ratios, inconsistent pigment dispersion or contamination during manufacturing can compromise performance. These defects might not be immediately obvious but can emerge under stress.

Choosing reputable manufacturers with proven quality control processes minimizes the risk of receiving substandard product.

Inadequate Adhesion

Inadequate adhesion can result from incompatible primers, lack of tie-coats between layers or exceeding recommended recoat windows. Each of these scenarios weakens the bond between layers, making them vulnerable to delamination. Over time, physical and chemical stresses exploit these weaknesses.

Proper system design and strict adherence to application windows help ensure full adhesion integrity.

3. Improper Application Techniques

Even the best coatings will fail if applied incorrectly. Application errors, like improper mixing, inadequate film build or poor environmental control during application, account for a significant percentage of premature failures.

Mistakes made at this stage are difficult to reverse. Careful planning, training, and quality assurance are critical.

Mixing Errors

Two-component coatings require precise mixing to initiate the curing process. Inadequate mixing results in unreacted portions, leading to soft spots, uneven cure or chemical imbalance. These flaws often go unnoticed until the coating is stressed, at which point it breaks down.

Using mechanical mixers, proper induction times, and batch tracking can help prevent these errors.

Incorrect Coating Thickness

Applying a coating too thin compromises barrier protection and may result in early failure due to erosion or pinholing. Conversely, applying it too thick can lead to cracking, solvent entrapment, or improper cure.

Film thickness should be measured both wet and dry using standardized tools. Target ranges are critical to achieve the manufacturer’s performance specifications.

Inadequate Curing Conditions

Curing is not simply a matter of time. It also depends on temperature, humidity and airflow. When these factors are suboptimal, curing slows or stalls, leaving the coating vulnerable. A partially cured film may look sound but fail under service conditions.

Accelerated curing methods or cure testing can confirm readiness before exposure.

Mistakes in Surface Preparation

Applying a coating to a damp, contaminated or improperly profiled surface negates all the advantages of high-quality materials. Adhesion will be poor, leading to disbondment. The coating may also trap moisture, causing blisters or internal corrosion.

Surface conditions should always be validated against specification before coating begins.

4. Environmental Factors

Environmental conditions during and after application play a crucial role in coating performance. Temperature, humidity, wind and UV exposure can either support or sabotage the curing and bonding process. Ignoring or underestimating these variables is a common cause of premature coating failure.

UV Radiation

Exposure to ultraviolet light degrades organic coatings over time, causing chalking, color loss and embrittlement. In outdoor or exposed installations, coatings not designed to resist UV will degrade rapidly, which may not only affect aesthetics but also performance.

A UV-resistant topcoat or specialized formulation should be selected for sun-exposed areas.

Humidity and Salinity

High humidity during application can lead to condensation on surfaces that interferes with adhesion and causes pinholins. In service, salty air increases the risk of underfilm corrosion and chloride contamination. Coastal and offshore installations are especially at risk.

Selecting moisture-tolerant coatings and controlling application conditions mitigates these threats.

Extreme Temperatures

Coatings are formulated to perform within specific temperature ranges.

Excessive heat during application and curing can cause rapid solvent evaporation, leading to poor film formation, while cold temperatures can inhibit curing entirely. Thermal expansion and contraction cycles also stress coatings, leading to cracking or delamination over time.

Monitoring ambient and surface temperatures during application and service is essential.

Strong Winds

Dust, sand and other airborne particles can act as abrasive agents, wearing down coating surfaces over time. This process is especially problematic in arid or industrial environments. As a result, coatings may lose gloss, develop pinholes or thin unevenly due to abrasive impact.

Applying sacrificial layers or abrasion-resistant coatings helps mitigate this form of wear.

5. Physical Damage

Wear and tear can take a significant toll on coatings, especially in high-traffic or equipment-heavy environments. Impacts, abrasion and concentrated stress points create vulnerabilities that can compromise the entire coating system.

Thermal Shock

Sudden and extreme temperature changes, such as draining and refilling tanks with water of a different temperature, can cause rapid differential thermsl expansion or contraction of the substrate and the coating. This mismatch in movement can lead to cracking, delamination or microfractures within the coating film. In severe cases, thermal shock can compromise the barrier in a single event.

Selecting coatings with high thermal cycling tolerance and applying gradual temperature changes during operation can reduce the risk of thermal shock–related failures.

Dynamic Loads

Equipment and structures that move, vibrate or shift place added stress on coatings. Repeated motion can cause cracking or delamination if the coating lacks flexibility or adhesion. Expansion joints, pump housings and flexible couplings are typical stress points.

Using high-flex coatings or elastomeric systems helps maintain integrity under dynamic conditions.

Abrasion and Impact Damage

Frequent cleaning, movement of equipment, particle-laden flow or sudden impacts from tools, machinery or falling debris can all damage coating surfaces. Abrasion gradually reduces film thickness, exposing the substrate to corrosion, while localized impact damage can create failure points that spread over time. Even minor or repeated impacts, though not always immediately visible, can create significant structural risks.

Coating systems with appropriate mechanical resistance for the environment can help mitigate both abrasion and impact damage. In high-wear or high-traffic areas, reinforced coatings, additional topcoats or protective barriers provide additional protection.

6. Ongoing Degradation

No coating lasts forever. Time, exposure and operational stress gradually degrade all protective films. Recognizing the natural lifecycle of coatings and planning for inspection, maintenance and renewal is essential to avoid sudden, unplanned failures.

Loss of Flexibility

As coatings age, their ability to flex and accommodate movement diminishes. This loss of flexibility can lead to cracking, especially in areas subject to thermal cycling or vibration.

Periodic evaluation for these issues helps determine when recoating is needed.

Blistering and Peeling

Over time, environmental exposure and underlying substrate changes can lead to the formation of blisters or cause the coating to peel. Unfortunately, once the protective barrier is compromised, failure accelerates quickly.

Regular inspections help identify early-stage defects and allow for targeted repairs.

Color Fading

Even when a coating remains intact, prolonged exposure to sunlight and UV radiation can cause significant fading, chalking or discoloration. In water and wastewater facilities with outdoor tanks, clarifiers or pipelines, UV damage can be accelerated by reflective surfaces such as water or light-colored structures.

While these changes may seem cosmetic, UV degradation can also embrittle the coating film, reducing its flexibility and protective properties over time. Incorporating UV-resistant topcoats or pigments into the coating system, along with periodic recoating of sun-exposed areas, helps maintain both appearance and long-term protection.

How to Prevent Premature Coating Failure

Avoiding coating failure begins with proactive planning and disciplined execution. From proper surface preparation to selecting the right materials, every step in the coating process must be carried out with care and precision.

Select the Right Coating or Lining System

The right type of coating system for a project depends on a range of variables including exposure type, temperature, chemical concentrations and mechanical stress. Consulting with technical experts early in the design phase ensures compatibility, minimizes risk and enhances long-term asset protection.

Meet Surface Preparation Requirements

Before applying a coating, it’s important to achieve the correct surface cleanliness and profile. A properly prepared surface improves adhesion, minimizes the risk of failure, and maximizes the coating’s life expectancy.

Following SSPC and NACE guidelines ensures contaminants are removed and the substrate is ready to accept the coating. Surface salt testing is equally critical, especially in coastal or industrial environments where chloride contamination is common.

Perform Quality Control Inspections During Application

Application quality is just as important as product selection.

Monitoring conditions such as humidity, temperature and dew point helps make sure coatings are applied under ideal parameters. Measuring wet and dry film thickness, verifying cure status and documenting process checkpoints all contribute to a successful outcome. Additionally, involving certified inspectors and trained applicators reduces error and elevates performance.

Follow a Preventative Maintenance Schedule

A proactive inspection and maintenance plan allows teams to catch early signs of coating degradation before they escalate. Routine visual checks, adhesion testing and touch-ups extend the service life of the protective system. When damage is identified early, repairs are faster, easier, and far less expensive. This disciplined approach preserves both the coating investment and the asset it protects.

Sherwin-Williams: Protect Your Water and Wastewater Assets with Confidence

Premature coating failure is preventable. By understanding the root causes, adhering to best practices and partnering with a trusted coating provider, water and wastewater operators can safeguard infrastructure for the long haul.

At Sherwin-Williams, we offer a full suite of high-performance coatings and linings formulated specifically for the water and wastewater industry. Our solutions are designed to withstand immersion, chemical exposure and mechanical stress common in water treatment facilities. We also provide expert technical support and specification assistance to help asset owners and contractors select, apply and maintain the right coating system for water and wastewater infrastructure.

Contact one of our experts today to learn how our tailored coating and lining systems can enhance your facility’s performance, extend the service life of water and wastewater assets and eliminate coating-related headaches before they start.