MIPA’s WB Coatings Protect World’s Largest Telescope

On April 8, 2024, large parts of the United States will be treated to a full solar eclipse, and many people are planning to travel to see the full eclipse. While this is a rare event, the skies are full of fascinating phenomena; pictures from the Hubble Telescope have brought our universe closer to us, at least visually.

In Chile, the world’s largest optical/near infrared extremely large telescope, or ELT, is under construction on top of Cerro Armazones, a 3,046 meter high mountain in the Chilean Atacama Desert.  The telescope’s dome is made of steel, and has to be stable, even during earthquakes, so the mirrors don’t go out of alignment. The ELT utilizes five mirrors, including a 39-meter main mirror consisting of 798 hexagonal segments.

Experts say that the ELT will be able to show images 16 times sharper than the Hubble Telescope. Construction began nine years ago; the first light images are expected by 2027.

There is a lot that goes into building the ELT. For our purposes, one of the interesting facets of the ELT is the coating that is required to protect the telescope from corrosion. The coatings also cannot create reflections, so a deep black paint with a dull matte surface was essential. The European Southern Observatory (ESO) selected WB Coatings, then a part of Warnecke & Böhm GmbH, which has since been taken over by the Mipa Group.

“WB Coatings was approached by the ESO headquarters in Garching, close to Munich, more than five years ago as they were currently looking for a suitable paint supplier,” said Marcus Preußner, general manager of Feycolor GmbH/WB Coatings (part of the Mipa Group). “After a successful meeting in Garching, ESO and WB Coatings started working on the concept of the coatings that had to be delivered. Ever since then, the successful cooperation has been continued.”

There are certainly challenges when it comes to a project of this magnitude, and WB Coatings has passed them all. Preußner noted that in terms of the lacquer itself, a series of different tests had to be passed.

“The first test panels were sent to an institute in the Netherlands for checking all the different criteria required by ESO,” Preußner said. “The tests included corrosion protection in accordance with corrosivity category C3 as per DIN EN ISO 12944-5 and a high expected duration of protection. The UV resistance was tested with 1,000 hours in a xenon test. Chemical resistance to various cleaning agents and disinfectants as well as coolants and lubricants was also checked in detail. Of course, apart from that, there were also the already high-quality standards and testing mechanisms of the Mipa Group in order to guarantee an impeccable product.”

Since the construction was carried out by an international consortium, the products were supplied to two participating companies in Spain and Italy, where the individual steel components were coated before being delivered to Chile for assembly.

“For the coating of the ELT, we were required to find products with excellent corrosion protection and consequently identified a system comprising of an EP-primer, a PU topcoat and a PU clearcoat to be the optimal choice,” Preußner reported. “The surface had to be black with a gloss level of 5 gloss units at a 60 degrees angle in order to reduce the reflection to a minimum. In the sector of matte finishes, MIPA has extensive experiences in car refinishing areas as well as the defence and security industry.” 

MIPA’s technical expertise in the field has proved to be a critical factor in the success of this project.

“We believe that our experience with many different industries and customers in combination with the expertise of our Research and Development department has definitely helped to find a suitable product and to guarantee the success of this part of the project,” said Preußner. “In the past, MIPA has already completed prestigious projects with similar requirements – for example the New National Gallery (Neue Nationalgalerie) in Berlin – for which it was also necessary to create special dull matt surfaces that meet many different demands.”