Sturdy Silica Coatings Take Tough Stance Against Corrosion

Engineers have long relied on polymer paints to slow metal corrosion, but these soft materials degrade, and their upkeep is costly. Now, researchers led by Jason J. Benkoski of John Hopkins University’s Applied Physics Laboratory have turned to inorganic chemistry to create long-lasting coatings that fight oxidation on multiple fronts. The coatings are water-based—allowing the team to spray them onto metals—but their inorganic contents, including silica, cerium, and zinc oxide, dry to form an insoluble film that’s stable in water and protects against corrosion. Silica provides a durable foundation, and cerium is a well-known oxidation inhibitor. The coating also fights heat, an important, but frequently overlooked contributor to corrosion, Benkoski told C&EN. Ships and other metallic vehicles often bear polymer paints that warm up in sunlight, accelerating their own degradation and metal corrosion. Zinc oxide in the new coatings reflects energy from the sun’s rays. Coupled with silica’s ability to emit thermal energy, the coatings passively cool themselves, Benkoski said. Coated surfaces didn’t warm much, even when they contained black pigments, which typically absorb heat.