SOFIA

SurTec Coats the Outer Cradle of the SOFIA-Telecope with SurTec 704 (Alcaline Non-Cyanide Zinc) and SurTec 680 Chromiting

Coating-concept: Dipl.-Ing. Bettina Kerle and Dr. Rolf Jansen
Security and transport: Dipl.-Ing. Severin Thamm
  Background:
SOFIA is a Jumbo-Jet Boeing 747 with an infrared telescope to do astronomical measurements. It shall enable the exploration of new born stars.
  A small component of the project is the Outer Cradle, which, together with other parts, enables the flexibility of the telescope.
The telescope is built by MAN, the Outer Cradle was produced by VOEST in Linz/Austria. The coating was done under the guidelines, active supervision on site and with processes by SurTec at the electroplating company Haslinger in Linz.
Several alternatives for the coating were considered: upright, axial rotated, completely or halfway dipped, laying, with or without agitation and so on. Finally it was determined: The wheelshaped Outer Cradle will be dipped completely and coated in a laying position.
 
The uncoated blank of the Outer Cradle has been delivered. SurTec-Engineer Bettina Kerle puts a first gaze on it.
 
The 800 kg weighting Outer Cradle has a caliber of nearly 3 meters. Careful handling is demanded: It values about half a million DM.
 
Mountings for the contacting and test panels are being attached.
  For pre-treatment, the Outer Cradle was manually cleaned with solvent cleaner SurTec 052 (PDF-file, 8 KB) and then pickled in hydrochloric acid together with the detergent pickling SurTec 425 (PDF-file, 16 KB).
After this, the huge ring was neutralized in caustic potash and water softening additive SurTec 954 (PDF-file, 40 KB) and lifted into the zincing basin.
The non-cyanide zinc electrolyte was prepared with KOH and SurTec 704 (PDF-file, 64 KB), to produce a preferably homogen metall distribution on the complex part.
 
Contacting and secure mountings are finally attached. In the background on the left, the electrolyte and pickling are waiting in the container to be applied.
 


The coating basins are used just one time!

 


The coating thickness has been measured – it is entirely the same size (25 ± 5 µm).

  The coating was done with approx. 2 A/dm2 in a round steel basin, which also represented the anode. That’s optimal for the “one way-zincing”. After the zincing, the part was rinsed well and then chromited with SurTec 680 (PDF-file, 56 KB). The trivalent thick layer passivation is a chemically extremly resistant coating, which is suited perfectly for the extreme demands in SOFIA.
  The valuable solution (zinc electrolyte, chromiting bath) was taken back by SurTec. The acid was used by Haslinger for neutralising purposes.

Bettina Kerle is also happy with the results.