The Role of Optically Active Pigmented (OAP) Coatings in Water Infrastructure Projects

Benefits of OAP Coatings for Industrial Coating Quality Control 

The use of Sherwin-Williams optically active pigmented (OAP) protective coatings and linings on water infrastructure projects can assist the third-party inspector when verifying that coatings have been applied accurately and efficiently. Since OAP is an inert raw material that does not react, it can be incorporated into virtually any coating chemistry. 

Detecting Defects in Water Infrastructure Applications with OAP Coatings 

When a coating is applied to water infrastructure, it is important to apply it at the recommended dry film thickness and have proper coverage of areas that require stripe coatings, such as edges, structural supports, welds and sharp angles. It is important to achieve a homogenous application to avoid formation of pinholes and premature coating failure. Pinholes and holidays, insufficient dry film thickness and poor application of stripe-coated areas can be identified by OAP technology.

How OAP Coatings Make Water Infrastructure Inspections Easier 

OAPs, when added to water and wastewater coatings, enable the coating to react to ultraviolet light—allowing for efficient non-invasive inspection of large water infrastructure projects without having a detrimental effect on the coating and verifying quality application in a timely manner. If an area is found to be defected with a pinhole or insufficient coating, the area will fluoresce, identifying the areas that need to be repaired or touched up.

Ensuring Proper Application of OAP Coatings with Ultraviolet Inspection 

Ultraviolet radiation is part of the electromagnetic radiation spectrum just outside the visible range and adjacent to the violet color of the visible spectrum. The wavelength for visible light is generally from 400 nanometers through to 760 nanometers. The wavelength for activation of OAPs is generally from 315 nanometers through to 400 nanometers. In the visible spectrum, violet light is in the range of 400 nanometers through to 420 nanometers. This is the typical violet light range for fluorescent coating inspection. When the optically active pigment has been added to the protective coating, the coating will glow when inspected using an ultraviolet lamp.

When inspecting a water infrastructure coating system with OAP technology, the SSPC Technology Update No. 11: Inspection of Fluorescent Coating Systems should be used. This standard discusses the technique and the equipment required to inspect.

Selecting Light Source Products for Inspection of OAP Coatings in Water Infrastructure Projects 

When selecting which type of lamp to use during inspection, reference ASTM E2501: Standard Specification for Light Source Products for Inspection of Fluorescent Coatings for guidance (1.1). This specification provides the requirements for light source products intended for excitation of fluorescent materials used as a system for detection of defects in industrial coatings. This includes the examination of both longer wavelengths fluorescing primer coatings as well as non-fluorescent top coatings.

As defined in the scope of the standard, the specification establishes the radiometric requirements of the light source product in terms of required wavelength range and minimum irradiance. Additionally, it establishes safety requirements for the light source product necessary to ensure the product will not pose a threat to visual health.

Improving Safety & Productivity with OAP Coatings in Water Infrastructure Projects 

Water infrastructure coatings formulated with OAPs can be made to fluoresce simply by illuminating the appropriate lamp or LED inspection flashlights. The LED inspection flashlights are often selected to enhance safety and workflow due to the flashlights being small enough to inspect behind hard-to-reach areas and designed as compact, rugged and lightweight. OAP coatings illuminated at the primer or intermediate coating level will show defects in application and in film coverage. Pinholes, holidays or low film thickness will either appear black in contrast to the fluorescing coating, or not as bright due to insufficient film thickness. OAP coatings illuminated after top coating will allow the glowing film to telegraph through the finish coat to show pinholes, holidays or low topcoat film thickness. There is no need to wait for the coating to cure, OAP coatings will illuminate even in a wet film as the coating film does not need to reach cure before checking for holidays.

A Full Line of OAP Coating Solutions from Sherwin-Williams

Sherwin-Williams offers a full line of Opti-Check coatings incorporating OAP technology. When using Sherwin-Williams coatings with fluorescing pigmentation that illuminates the coating for instant verification under ultraviolet light on your water infrastructure projects, you gain the following benefits: 50-70% improved productivity, 25% more defects revealed, improved visibility of low film thickness on edges and pinhole defects visible from 2x standoff distance.

Partner with Sherwin-Williams on Your Next Water Infrastructure Project and Experience the Benefits of OAP Coatings

At Sherwin-Williams, we understand how important it is to get water infrastructure projects done right. Achieving long-lasting protection and corrosion resistance isn't just about choosing the right coatings—it’s about ensuring they’re applied properly. That’s where our Opti-Check Technology can make all the difference.

Our OAP coatings offer a simple yet powerful way to improve quality control. With pigments that illuminate under UV light, you can quickly check for any issues like pinholes or uneven coverage. This means faster inspections, fewer mistakes and a smoother project from start to finish.

When you work with us, you're not just getting high-quality products—you’re partnering with a team that cares about your success. Contact Sherwin-Williams today to learn how our OAP coatings can help your next project run smoother and deliver better results.