Where the
world gathers for metal finishing
Q&As since 1989


-----

Vacuum evaporation on glass beads

2006

Dear Sir,
(We are having an vacuum evaporation coating plant, (for coating on glass beads).
At present we want silver bright coating on glass beads ,we tried using chrome powder & aluminium strips to get silver coating,at temperature 250 °C to -5 to 5.5 vacuum we achieved it, but after putting glass beads in acid it turned to black - jet.(i.e., base colour)As aluminium coating is very thin it wears out quickly.
Therefor my question is what other metals or powders which is strong enough to get silver bright coating through vacuum evaporation process on glass beads,and should not be affected by any acids.
Thanking You,
Yours faithfully,

Mustafa Bakkallah
- MUMBAI, (Maharashtra), INDIA

To achieve resistance to "any acids" you will have to deposit a relatively thick coating of a noble metal such as palladium, platinum, rhodium or an alloy of white gold. All conventional metals and alloys will be attacked by acids.

Guillermo Marrufo
Monterrey, NL, Mexico
2006