Spanish nano-coating could replace toxic chromium shield on European satellites
A CSIC-backed team has produced a gold and silver nanoparticle film that outperforms the hazardous coating long used to protect satellite components, offering Europe's aerospace industry a cleaner alternative just as regulators push to ban the incumbent material.
A research team at Spain's CSIC, working through its spin-off Nanostine and with backing from the European Space Agency, has developed a nanoparticle coating that suppresses the multipactor effect, an electron avalanche inside satellite antennas and waveguides that can permanently destroy communications hardware. The coating, made of gold and silver particles just four to eight nanometres wide, outperforms the chromium-based compound that has been the industry standard for decades.
The multipactor effect has sat on ESA's list of technical concerns for more than 40 years. It occurs in vacuum, when stray electrons strike a surface and release yet more electrons in a self-sustaining cascade, eventually burning out the component. Until now, the default fix has been Alodine, a chromium-based treatment that protects effectively but poses health risks to workers and environmental hazards, prompting European authorities to press for its prohibition.
No alternative had matched Alodine's performance, according to Lidia Martínez, a CSIC researcher at the Institute of Materials Science of Madrid. The sector, she explains, needed a substitute that would emit very few secondary electrons, since those are what trigger the chain reaction. Previous attempts modified surfaces at the micrometre scale and fell short of what the space industry demanded.
A question of scale
The ICMM team shifted to the nanometre range. Using a gas aggregation source, an ultra-high-vacuum technique that deposits material without solvents or residues, they built porous, chemically clean metallic films. In tests conducted at ESA-accredited laboratories, the new coating reduced secondary electron emission by roughly 30% compared with Alodine. In certain configurations, the cut-off energy threshold, the point at which a material begins generating more electrons than it receives, improved by up to 300%.
Durability tests also looked encouraging. After six months of ageing and thermal cycling at 150°C, conditions similar to those a satellite faces in direct sunlight, the coating's performance dipped slightly but still exceeded that of freshly applied Alodine.
Commercial road ahead
CSIC and Nanostine filed a joint European patent application with the European Patent Office in July 2025; it is currently under examination. Nanostine, created by CSIC itself, will handle commercialisation, targeting the aerospace sector primarily. The work was funded in part by an Industrial PhD programme run by the Community of Madrid and supported by the ESA Business Innovation Centre, coordinated in the capital by the Madri+d Foundation.
Martínez cautions that the path from laboratory result to flight hardware is long. Qualifying a new coating for actual use in orbit typically takes around a decade of testing and validation. She notes that ESA has expressed satisfaction with the solution, but stresses that several stages remain before the material can fly aboard a satellite.
For Europe's growing constellation of telecommunications and Earth-observation satellites, the stakes are practical as well as environmental. A compliant, higher-performing shield manufactured on the continent would reduce reliance on a substance facing regulatory phase-out while strengthening the supply chain for an industry that Brussels regards as strategically essential.
