very black anodizing

A local company makes some devices for aiming xray machines. The
device projects a cross hair where the xray beam goes. Anyway on a new
model some of the light bounces off a black anodized surface and
reduces the contrast as well as showing up outside of where the light
should be. They are looking at various ways to fix this. And one way
might be to just use a better black anodize. Redesigning the part can
be done, but there are a lot of constraints on doing that.
Rummaging around on the internet, I found a few old references to
Martin Black and Ball Black being coatings especially made for
adsorbing light. Martin being Martin before it merged with Lockheed.
And Ball being Ball Aerospace. Does anyone have any experience with
either of these finishes? And is either of them licensed to commercial
anodize firms? Or would one have to send the parts to Ball Aerospace
in Colorado?
Dan
P.S. if you want to email me direct, my email address is dlcaster57 @
yahoo. com without the spaces.
Reply to
dcaster
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would it be possible to mask the part off and spray it with a matt black lacquer paint?
Reply to
Stealth Pilot
Are the parts "shiny" before being anodized? A dull finish would make more of a flat black anodize. Anodizers may have an acid bath or something to do this, I don't remember for sure. Randy
Reply to
Randy Replogle
I work at the Lockheed plant that developed "Martin Black", and have seen it.
It sure looks like paint to me, I don't think it is an anodize process but I don't know for a fact.
Anodized surfaces are generally pretty shiny.
A.P mentioned flocking. Flocking would work fine in a clean environment but holds dust, cobwebs and other junk that may be present and cna be difficunt to clean. Depends ont the environment.
Flat black paint (Martin Black) may be better in a dirty environment
Carl
Reply to
Carl Boyd
Absolutely no experience with the process, but could you glass bead or abrasive blast the offending surface prior to anodizing? Would that produce a less reflective surface?
Reply to
Bill Marrs
Many of these coatings are mechanically quite fragile. Is this an issue?
The best widely available cheap black coating is Krylon Ultra-Flat Black paint (type 1602), available in most hardware stores, in the spray-paint dept, so I would try this first.
If 1602 doesn't solve the problem, you might try your question over on "sci.optics".
Joe Gwinn
Reply to
Joseph Gwinn
How about gluing some photographers black cloth on the surfaces?
--.- Dave
Reply to
Dave August
No experience with those finishes, Dan.
Aluminum is reflective. The two ways to make it non-reflective are to cover it with a nonreflective coating or do what one can to minimize that property of the metal.
If the metal surface is altered by abrasion or blasting, then specular reflection is greatly reduced because much of the light is reflected off-angle and not back at the viewer. Further, if it is then black anodized, there is much more surface area to anodize so more black dye is retained per unit of surface area. The dye itself is very black. This still won't be as black as black flocking, but it's a lot blacker than otherwise, probably as good as or better than most flat black coatings and considerably more durable.
Reply to
Don Foreman
Given the experience of makers of photo equipment over more than a century, it's clear that the levels of light absorption needed in critical optics applications is very high. They use applied, paint-like coatings, even though they're often coating aluminum.
I really doubt if any conversion coating you could put on aluminum would achieve the level of absorption required, for example, to maintain contrast with a multi-element lens. Those coatings just aren't made for the job.
-- Ed Huntress
Reply to
Ed Huntress
The makers of photo and optical equipment calls this stage in production FLOCKING Flocking = make the inside black and nonreflective. Maby some Googling on Flocking can take you closer to a solution ?
AP
Reply to
A.P.
On Sat, 04 Nov 2006 15:32:07 GMT, with neither quill nor qualm, "Bill Marrs" quickly quoth:
Yes. I used to inspect black anodized instrument panels for Southcom, Int'l. back in the 70s. They were brushed and beaded aluminum and the brushing & beading made the anodizing look considerably more dull.
-- "Not always right, but never uncertain." --Heinlein -=-=-
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Wondrous Website Design
Reply to
Larry Jaques
Snipped from one of Uncle Al's posts
"The blackest stuff I've ever seen is micronized copper chromite catalyst - black so black it sucked your eyes in, too black to remember accurately. Of course, that is only perceptual. If you want really black paint you take black matte and add hollow (not solid, hollow!) glass microballoons to blacken it some more (in the visible)."
Reply to
Boris Mohar
Good idea, but in this case probably not useable. I should have put more emphasis on this being used with xray machines, and high powered xray machines at that. The radiation is likely to cause paints and flocking to deteriorate rapidly.
Dan
Reply to
dcaster
They would rather not use any paints as the radiation ages them rapidly.
Dan
Reply to
dcaster
The part is currently cnc machined and the surfaces that cause the problem are nice and smooth. One of the solutions may be to change the shape of the part so that the light is reflected where it is not a problem. Bead blasting is also a possible solution, but the place that does the machining is not set up for doing that. So that means the part would have to be sent somewhere before being sent to the anodizer. I was hoping to find that the part could be used as is, just with a different dye being used at the anodizer. And that may still be the case. I was hoping that someone here would know something about Ball Black before I start calling people.
Dan
Reply to
dcaster
I have never seen Martin Black, but vaguely remember reading about it a long time ago. And I remember it as being a paint too, but the references I found on the internet described it as an anodize. So I thought my memory was bad...........
Dan
Reply to
dcaster
I am not sure. I found some references on the internet that put black anodize as .87 emmisisity and Ball Black as .94. That may or may not be enough difference to make the part acceptable with only changing the anodizing. It probably would have been good enough, but now they are looking for stray light. So it may not be enough difference now.
Dan
Reply to
dcaster
One thing that may work and can be done in-house is to use a random sander with scotchbrite. I used to make parts that had to be finished this way, the parts needed to have a mat finish with no tooling marks visible. The way I did these parts was with the typical electric sander that had both random and straight sanding directions. The sander used pre-cut rectangular sheets of sandpaper. I used the roughest sanpaper available to grip the scotchbrite. Just set the scotchbrite on the part and place the sander on the scotchbrite. I think that you can now get the stuff with velcro on it for even better grip. Sometimes two grits of scotchbrite were needed. One to rough in the finish and a finer one for the final finish. Cheers, Eric
Reply to
Eric R Snow
Can they do acid etch?
What about machining it from black Delrin? It rates pretty high in emissivity.
Best regards, Spehro Pefhany
Reply to
Spehro Pefhany
Get some flat or matte phoyosensitixes aluminum from Horizons (google). Expose to daylight, develop in film developer or buy their's, Boil in their non tinted solution, and use that to cover the effected areas. Or just buy it from them. It's called Metalphoto.
Reply to
daniel peterman

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