Testing Coating Performance

In 2019, Worthington Steel Metallurgist Dennis McHugh set out to answer a simple but critical question: How do our coatings perform in the elements, especially in the Midwest, where many of our customers operate?

Traditional salt spray tests provide quick, controlled insights. Still, they can't replicate the experience of grain bins in wet fields, solar frames under constant sun, or panels facing daily condensation cycles.

So, Dennis built something new: an outdoor testing station at our Delta, Ohio, facility to serve as a constantly evolving, open-air laboratory. By testing our steel outdoors, Worthington aims to help customers better understand how their coatings will perform and make recommendations on outdoor storage for formed parts.

"The idea was to give customers a real-life example of the passivation products we offer," Kaitlynn Clody, a metallurgist at Worthington Steel, who now oversees the testing program, said. "This isn't simulated, it's what actually happens to the coatings over time."

At first glance, the Outdoor Testing Station might seem like rows of metal samples set in a field. But each 4x6-inch panel has its own story about durability, corrosion resistance, and long-term performance.

To measure the coatings' performance, Kaitlynn and her team monitor each sample's surface gloss with a handheld meter at consistent intervals and the composite's overall appearance.

The current collection includes coatings such as:

"The initial gloss readings of the sample are insignificant," Kaitlynn said. "It is the slope, or changes, of the glossmeter results that show us how the passivation product holds up over time. A steeper slope correlates to a quicker degradation of the product."

Initially, the testing frequency is every one to two weeks, then monthly once the results start to stabilize. The team also captures high-resolution microscope images every six months to identify early signs of white rust, a sign of coating breakdown.

Combining both the gloss readings and the visual appearance, Worthington can surmise which coatings tend to weather faster, lose their metallic silver appearance, and when specific samples develop white rust.

Some of these samples are purposefully stacked or bolted to show how coatings behave over time, insights we use to help you choose material. Samples also represent different years. Many originate from Dennis's first round of testing in 2019, and then others were added in subsequent years.

The team routinely evaluates the value of keeping old samples, such as passivation products that have sunset or duplicates of other coatings and adding more for easier comparison to keep the collection relevant.

This data-driven approach provides Worthington Steel with a deep understanding of how our coatings have behaved over the years and enables us to build a knowledge base.

The Delta station helps Worthington metallurgists across the company make recommendations to customers about coating choices.

When a customer encountered unexpected white rust on their steel, Kaitlynn's team used the testing station results to identify which coatings resisted moisture best and to recommend alternatives that best aligned with their use case. "It's confidence-building," she said. "Customers can see that our recommendations come from real, long-term testing, not just simulations."

To capture and showcase this data, Kaitlynn creates a chart, such as Figure 1, that shows the gloss readings over time for popular passivation products. This data is how metallurgists, as in the example above, can make recommendations on coatings based on the length of time a customer's product is intended to remain on a job site.

The testing station also includes steel samples without any passivation products, allowing customers to see how unprotected material performs over time to help determine whether they need coatings for their applications to prevent corrosion.

Not only has the Delta team used it for customers, but it has also been used to trial new coatings on our steel against the original, evaluating variables such as white rust formation, metallic appearance, and longevity.

Trialing currently at the facility is a new trivalent chromium passivation product that is a safer, more sustainable alternative to a traditional hexavalent coating. Before it can replace the original, it needs to match or exceed those performance variables utilizing the glossmeter data.

By letting the weather do the testing, the result is a continuous feedback loop of testing, validation, and improvement to ensure Worthington's coatings perform.

Among the many coatings tested, one has consistently stood out for its resilience: acrylic.

Unlike chromium-based treatments, which are a film on the surface of the steel that can be washed off over time, acrylic is cured to the strip. It is secured by mechanical anchoring and chemical bonding, creating a thicker barrier between the base material and the elements.

"The acrylics last significantly longer," Kaitlynn explained. "They're part of the strip itself; it's not going anywhere."

This makes acrylic coatings ideal for harsher conditions where water, salt, or temperature fluctuations are constant. Even after multiple winters and summers on the test stand, acrylic maintains its gloss and visual integrity over time far better than traditional coatings.

As seen Figure 2, the 2020 coated acrylic can hold for years before seeing a drop in gloss from the reader. From 2020 to 2023, there was only a loss of around 50 gloss units (GU) measured by the glossmeter, the least dramatic rate of decline among coating options.

After a year of testing the samples, white rust was observed microscopically in all but the acrylic sample. Even after a year and a half, when most samples continued to show white rust growth, acrylic continued to protect the material.

With this information readily available, the Worthington team can make recommendations to our customers who need their steel out on a job site for longer or whose product faces extreme conditions. For those who need protection, acrylic coatings will last the longest.

They're also preparing to add competitor steel samples, not to compete publicly, but to benchmark performance and strengthen internal validation for Worthington's coating portfolio.

"As we trial new formulations or work with different chemical suppliers, the stand lets us make smart, data-driven decisions," Kaitlynn said. "It ensures any product changes or consolidations don't affect quality."

What started as one metallurgist's idea has grown into a cornerstone of Worthington Steel's customer support and product development. Over five years, the Outdoor Exposure Testing Station has evolved from a small innovation into a trusted proving ground for passivation and coating performance. The lessons learned there directly inform us what Worthington offers today and how it helps customers make informed, confident decisions for tomorrow.

For Kaitlynn, the station's purpose goes beyond science. It's about trust.

"It's not just testing," she said. "It's showing customers that we've done the work, and we can prove what we say."