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"How to protect silumin (aluminum with silicon) from corrosion"


Dear colleagues,
During the maintenance of a radiofrequency telescope settled on a sea shore there arose a problem of a corrosion of a reflector made from silumin.
Question: what electrically conducting coating can be used for its corrosion protection?
Appreciate your response.

Kirill Levine, PhD
NDSU - Fargo, ND, USA


I don't know of a really good answer, Dr. Levine, but I understand that you can Ivadize (deposit pure aluminum in a vacuum chamber) and get better corrosion resistance and better reflectivity than the aluminum alloy offers. I'm not really sure of this as a solution though, and it could only work if the mirror can fit in the vacuum chamber.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


Ted, this is a radiofrequency telescope, not an optic scope, so electroless nickel would be an option. A thin gold plate would be a better option, but probably much too expensive. I also think of these as being massive sized, so that would certainly cause many constraints.

James Watts
- Navarre, Florida


Thank you colleagues, I really appreciate your feedback. This is indeed a massive Kassegren mirror of hyperbolic shape of 1.5 m diameter. They were thinking about some organic conducting coating, but there is no much choise of commercially offered options.

NDSU - Fargo, ND


You might possibly get by with cleaning the mirror and applying a coat of a hard wax like carnuba wax. A soft wax will probably attract dirt over time. The wax should significantly slow down the corrosion/oxidation of the aluminum. I doubt if it would have an effect on the efficiency of the mirror for radio signals, but it might and it is certainly not conductive, but is thin. I would run some lab testing before I got carried away. There are several places in the US that have EN tanks big enough to do your mirror, but, most of them are set up for preplate processing of steel. Look around, you might find one. Not cheap!

James Watts
- Navarre, Florida

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