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Coating aluminium on glass beads by PVD process

Q. Dear Sir,
I have vacuum coating machine and we coat aluminium on glass beads. After coating aluminium by PVD Process 10^-5 vacuum we get good results, but when we put in nitric acid or subjected to air it corrodes quickly so I would like to protect my coating from corrosion. So what other metals powders should I deposit on Aluminium to avoid corrosion. My coating also wears out when it is polished in vibrator machine. Please Help
Mustafa

Mustafa Bakkalla
- MUMBAI, MAHARASHTRA, INDIA
January 1, 2012

Aluminum reacts with nitric acid. Avoid contact with it. Aluminum is a soft metal. It would certainly wear out during polishing. Finish all polishing before coating. Normally exposing to air should not corrode Al coating. Probably coating is not properly adhering to the glass beads. A thorough cleaning and drying of the beads prior to coating would help. Heating the beads during coating would be beneficial. You may try a protective coating of SiO2. But I doubt if it solves your problems. Good luck!

H.R. Prabhakara - Consultant
Bangalore Plasmatek - Bangalore Karnataka India
January 12, 2012

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