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  #21  
Old 03-06-2019, 09:19 PM
Hemi
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Hey to all,

As some might know from another thread my C925 Aluminium tube has a large dose of Corrosion, covering the inside of the tube.

Ive deconstructed the entire OTA, to leave just the Alu tube. I sanded it and have painted it with a flat black anti corrosion spray (2 coats).

It really is flat matt black, far darker than the original. However it is ever so slightly rough and fine black dust sheds with a light touch/brush. Ive washed it thoroughly and now it takes a fairly pressured finger, but there is still some black paint dust.

I agree any sealer will just gloss it up. This Black 2.0 or 3.0 doesn't seem to be the answer either. Protostar (a US company) does this Flock board which springs to shape of the tube without adhesive etc. Might be better for some applications. Especially in hot humid climates where the adhesive of flocking material doesn't last.

Cheers

Hemi
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  #22  
Old 05-06-2019, 01:05 PM
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mental4astro (Alexander)
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Hemi, something rather odd going on there with your paint. It should not come off when touched, nor should you have needed to wash it. Why did you feel the need to wash it?

Is the paint made for applying neat to aluminium? The photo of the tin says bare ferrous metals or prepainted metal, and the Dulux site is ambiguous about applying it to neat aluminium (real pain in the neck! ). Aluminium requires a special primer different from ferrous.

I've used this same Dulus epoxy spay, also 2 coats, albeit white, and found it did not come off at all. I painted steel counterweights and experienced no shedding of paint from my subsequent handling of the counterweight, and it's been 6 months so far and the counterweights have also been hot, cold and soaked with dew.

Where did you see that Black 2.0 or 3.0 is not an answer? If you've found info supporting this please let us know, because so far the testing I've done with Wavy has not been negative. Wavy and I are not painting onto bare metal, but painting over either primed or pre-painted surfaces. If you've found negative experiences with applications like our own unique astro one, please let us know where so we can see what is going on and figure out the ultimate astro application for Black 2.0 and 3.0. I've got a small cheaparse little Newt and a small refractor I'm putting up as guinea pigs.

Please don't feel I'm having a go at you or defending any product! If your experience with that Dulux product was poor , we need to know why things went pearshaped, especially when my experience with it was a positive one. Were conditions hot when you painted the tube? Most curious that it should come off when you ran your finger over it!

Alex.
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  #23  
Old 05-06-2019, 01:25 PM
Hemi
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Hey Alex,

No experience of black 3.0 or 2.0. (in fact im on the wait list for 3.0), I was just responding to the thread, where one post suggested that 2.0 was fragile and flaked. Would be very happy indeed if it is suitable for my application.

Regarding the epoxy that I used. I didn't sand down to bare metal everywhere, just at the corrosion areas, the spray says its a one stop solution, primer not required. The paint chap at Bunnings also said the same. I sprayed 2 coats 90mins apart (as instructed on the tin), let it dry for 24+ hours. And then examined it, where I found the fine dusting on light touch. I washed it, as the paint had a roughness that made a microfibre cloth cling and impossible to use.

In any case, a member on Cloudy suggested that I should wait as this paint can take a long time to dry thoroughly. I think he was correct, as the paint is not dusting off any more. Not sure if thats because I washed all the debris off, or just that it has dried completely.

Ive ordered the flocking material I posted about, it was fairly inexpensive (50USD inc shipping). But I think the paint has worked and the OTA is ready to put back together (GULP!!)

Cheers

Hemi
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  #24  
Old 05-06-2019, 01:55 PM
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mental4astro (Alexander)
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Hemi, please re-read my post as I said the poster paint came off, but the 2.0 held fast.

Yes, that Dulux epoxy paint does take a LONG time to dry! My experience too We get used to very fast drying paints, and more specialized paints can take much longer. But that it should have make a dust for you is most curious.

Nick painted a board one side with 2.0 the other with 3.0. The 3.0 is significantly "blacker". We now have a donor Newt that we'll paint with the Black 3.0. We are now on the lookout for a donor frac. We'll be subjecting these test scopes to the same conditions as our own gear, in storage and out in the field, and see how the paint handles these conditions after some time. If anyone in Sydney has a little frac they would like to donate, please let either Nick or myself know.

Alex.
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  #25  
Old 05-06-2019, 04:10 PM
Hemi
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Thanks Alex, I always read and re read your posts

I was referring to Nicks (wavytone) experience of 2.0

Cheers



H
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  #26  
Old 06-06-2019, 01:45 PM
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sil (Steve)
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Good to see the comparison there. To my eyes I still call it dark grey. black anodised aluminium is a deep black to me though reflective so unsuitable here. I guess you could take before and after images and measure if the black yields any appreciable differences in apparent magnitude, but hard to do under identical conditions. Maybe if you have an unadulterated ota to equal the donor one and image using both in the same session? or maybe a spectroscopy test with a laser pointer and see how absorbant of photon energy it is, or some other better test. at least it being blacker than 2.0 is good.
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