Zinc-Silicate Coating Blocks Corrosion

Spinoff is NASA’s annual publication featuring successfully commercialized NASA technology. This commercialization has contributed to the development of products and services in the fields of health and medicine, consumer goods, transportation, public safety, computer technology, and environmental resources.

In a recent test at Kennedy Space Center, engineers applied environmentally friendly coatings to steel samples. After 18 months’ exposure in the salty sea air, the Polyset-coated samples (bottom) remained nearly pristine, while the ones coated with another product became riddled with rust and corrosion.

NASA needs materials that are strong and can hold up over time. Sometimes that means designing new materials, but sometimes NASA sticks to industry standards like steel, and creates a game-changing coating to protect it from the elements. That’s what happened in the 1970s, when a team at Goddard Space Flight Center developed a mixture of zinc powder and potassium-silicate to protect metal surfaces from corrosion.

Zinc had long been used in anti-corrosion coatings, but NASA wanted something that was easier and more cost-effective, so Goddard chemist John Schutt began to adjust the formula. The final product did more than cover the metal to block sea spray, fog, or other corrosive elements — it actually chemically bonded with the underlying material. In other words, once you apply the coating, it becomes part of the parent steel. The result was an incredibly effective and durable treatment that didn’t even allow water damage or corrosion to seep into protected areas if the coating was scratched or incomplete.

NASA put the coating to use on structures at Kennedy Space Center, where it protects launch facilities not just from the salty, tropical environment, but also from the temperature spikes and high-heat exhaust of rocket launches.

But NASA wasn’t the only organization with structures to protect. The coating was soon put to use on a range of metal structures, from bridges and boats, to the Statue of Liberty. To sell the coating in the private sector, NASA licensed its patent to Inorganic Coatings. But before the company could produce the coating commercially, it had to perfect the manufacturing of liquid potassium-silicate.

Polyset sells its coating to companies that operate offshore oil rigs like this one, which can suffer corrosion from the seawater.

Inorganic Coatings turned to another company, Polyset (Mechanicville, NY), for help. Polyset then signed an agreement with Inorganic Coatings to provide them the liquid silicate exclusively for the NASA-derived coating. When Inorganic Coatings later tried to produce the silicate itself to save on costs, it was unsuccessful, and the faulty product it produced helped put the company out of business.

Later, other companies began making the coating, using liquid silicate manufactured by Polyset. History repeated itself, and once again, the product was faulty. But the NASA formula, when manufactured correctly, was still the best product available to prevent corrosion of metals, and Polyset was the one company that had the ability to produce the key ingredient consistently.

So in 2010, Polyset decided to take the coating directly to market under its own brand name: WB HRZS Single Coat System, where the acronym stands for water-based high-ratio zinc-silicate. It created a new protective coatings division. One of Polyset’s first customers for the coating was Chevron Oil, which is using it to protect its offshore oil rigs.

A single coat will prevent problems, even in the splash zone, which is highly susceptible to corrosion. The Chevron representative was skeptical, but agreed to test a small patch on a rig in the Gulf of Mexico. The test area had remained pristine, even though the rest of the metal was corroding all around it. The chemical bond also adds another benefit: it allows the surface to be electrically conductive, which deters marine critters, like barnacles and mussels, from clinging to the surface.

Another benefit is that unlike many other inorganic coatings that must be applied in a single pass or sandblasted off to try again, WB HRZS can bond to itself, so if the first coat is not thick enough, it is simple to go back and fix. And although just a thin coat of six- to eight-thousandths of an inch is required, there is no harm if some spots end up thicker, unlike with other inorganic zinc coatings that crack when over-applied. And because it is water-based, it’s a lot safer and more environmentally friendly than coatings that include solvents or thinning agents.

Polyset is working on expanding its customer base among companies that make ships’ hulls and interiors, as well as rail cars, hydroelectric plants, and bridges, and it is also going through the process to become an approved supplier for the Department of Defense and Department of Transportation.

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