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Aluminizing coating has a black tinge
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Hi Guys,
I am new to the group and have just started to play around with aluminizing mirrors. I have a system which I managed to scrounge and can achieve a vacuum of around 1x 10-4 torr. The first experiment produced a really good aluminium coat. At this stage I thought this is really easy. Pride goeth before a fall, my second try produced a coating with a very dark tinge to the coating. Anyone have any clues as to what might be wrong. Any help would be much appreciated. regards Joe |
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Ken Hunter
Hello Joe,
Welcome to VacuumX! Try looking through the past posts and the resources to the left side of the Groups main page. There are a lot of hits if you search for "black coating" Here's a snip from message 237. It may not be your problem but there's a lot more to read about this subject. * If you find yourself having "black" coatings, try implementing a third "Pre-Heat" option. I recently ran into a string of failed coatings. While I had originally thoughtthe problem was contamination, I now believe the problem was a result of my rapidly heating the filaments up due to a lack of humor and the resulting impatience that followed. The work around for the string of failed coatings has been a more controlled ramping up of filament tempature instead of my "frustrated, full throttle, get it done" approach I had during my string of failures... :) My supposition is that while loading the filaments, some contamination is inevitable. A pre-heat session boils off the contaminents and gives the pumps a chance to remove the material from the chamber enviroment. Another possibility is the pre-heat and slow ramp up allows for an opportunity for the removal of residual H20 that clings to the surfaces inside the chamber. In any event, while not an expert, I do know that gentle application of filament power produces a nice coating. A rapid "get it done" application of filament power results in a non-reflective flat black coating :0 * Also search for "discharge cleaning", Off hand, I'd think you'll need a bit deeper vacuum in the chamber to get consistent results... Again, Welcome to VacuumX ! Ken Hunter --- In VacuumX@..., "joeblack19502000" <joeblack19502000@...> wrote:
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Aurigema, Andrew N. (KSC)[ASRC AEROSPACE]
开云体育Oh yes.
?
If you dont get the air out of the chamber you will make
the most lovely shade of black aluminum.? Do you burn all your emitters at
once.? burning the emiters in groups ( like I do ) means I have to wait for
the pressure to drop between each group.? The first burn kicks water off
the walls.??
?
I pull vacuum overnight now to get the water off the
walls.? Then the second day I pull hard vacuum and it really does help
out.?
?
Andrew in soggy Florida ? From: VacuumX@... [mailto:VacuumX@...] On Behalf Of joeblack19502000 Sent: Thursday, August 07, 2008 10:02 PM To: VacuumX@... Subject: [VacuumX] Aluminizing coating has a black tinge Hi Guys, |
开云体育Don’t forget that hot Al is a “getter” too, so it will scavenge stuff and trap it in the molten metal, so when it finally evaporates you get all that crap back, just when you need it least! ? One thing, mentioned before, 1 x10^-4 is a little high pressure wise for reliable coating, see if you can get down to 10^-5 or -6 range, might take a bit longer than your current pump down though. One thing you didn’t mention was whether you discharge clean before coating, if not you should try to set up to do so, it will make for better coatings and faster pump downs (you will have less adsorbed water in your chamber to deal with for one). ? Good luck. ? Cheers, Thomas Janstrom. Little Gems. www.tjlittlegems.com ? -----Original
Message----- From: VacuumX@...
[mailto:VacuumX@...] On Behalf Of
Aurigema, Andrew N. (KSC)[ASRC AEROSPACE]
Sent: Saturday, 9 August 2008 2:03 AM To: VacuumX@... Subject: RE: [VacuumX] Aluminizing coating has a black tinge ? Oh yes. ? If you dont get the air out of the chamber you will make the most lovely shade of black aluminum.? Do you burn all your emitters at once.? burning the emiters in groups ( like I do ) means I have to wait for the pressure to drop between each group.? The first burn kicks water off the walls.?? ? I pull vacuum overnight now to get the water off the walls.? Then the second day I pull hard vacuum and it really does help out.? ? Andrew in soggy Florida ? ? From:
VacuumX@yahoogroups Hi Guys, |
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--- In VacuumX@..., "joeblack19502000"
<joeblack19502000@...> wrote: Thanks for you help Ken, Andrew and Thomas, you have given me a lot of food for thought Best Regards Joe |
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Aurigema, Andrew N. (KSC)[ASRC AEROSPACE]
开云体育I just got the discharge cleaning transformer working again
this weekend and wow what a difference that thing makes.?
?
My chamber fills with a purple haze of death that sparks
and flows and glows for about 2 hours then it just fades away as the pressure
gets lower and lower.? When the purple haze is gone........... it is time
to evaporate aluminum.? There is not a huge pressure spike when the first
emitters go off either.? It really did not add any more time to the pump
down cycle as the energy added lots of particles to the stuff clinging to the
stuff on the wall.
?
It is only a $30 "beer sign" transformer but it do earn its
own keep.?
?
Andrew? in soggy FLA From: VacuumX@... [mailto:VacuumX@...] On Behalf Of Thomas Janstrom Sent: Friday, August 08, 2008 9:51 PM To: VacuumX@... Subject: RE: [VacuumX] Aluminizing coating has a black tinge
Don’t forget that hot Al is a “getter” too, so it will scavenge stuff and trap it in the molten metal, so when it finally evaporates you get all that crap back, just when you need it least! ? One thing, mentioned before, 1 x10^-4 is a little high pressure wise for reliable coating, see if you can get down to 10^-5 or -6 range, might take a bit longer than your current pump down though. One thing you didn’t mention was whether you discharge clean before coating, if not you should try to set up to do so, it will make for better coatings and faster pump downs (you will have less adsorbed water in your chamber to deal with for one). ? Good luck. ? Cheers, Thomas Janstrom. Little Gems. www.tjlittlegems. ? -----Original
Message----- ? Oh yes. ? If you dont get the air out of the chamber you will make the most lovely shade of black aluminum.? Do you burn all your emitters at once.? burning the emiters in groups ( like I do ) means I have to wait for the pressure to drop between each group.? The first burn kicks water off the walls.?? ? I pull vacuum overnight now to get the water off the walls.? Then the second day I pull hard vacuum and it really does help out.? ? Andrew in soggy Florida ? ? From: VacuumX@yahoogroups Hi
Guys, |