ok, so this is a strange place to ask this question, but I suspect someone here will know the answer. I'm starting a new, ambitious project build called "wopr" which has sort of been inspired by the movie war games. I've been thinking a lot about the exterior finish of the case, and I think I know just what I want, but i'm not sure what it is called, and for once, google has failed me! I want the black (powdercoated?) finish you sometimes see on old military or optical equipment... think back to your 8th grade microscope, or old, metal binoculars, old cameral housings... you know what I mean? it is black, fairly thick, "orange peel" texture and hard... so hard, I think it is applied first, then the piece machined. it usually seems to be to coat alumninum stuff. I think it is a thick powdercoated finish, but according to my research, powdercoating started in the 60's, and I seem to think I've seen the finish I"m talking about on older stuff--WWII era. anyone know for sure?
I love the movie war games, btw. i would guess the coating is just thick coat non-environmental-safe paint. or maybe black anodizing.
You can achieve that effect with enamel, powder-coat, or by baking on a plastic layer. All of which are applied after the material is machined.
upon further discussion I had a converstation with a friend, I think i've discovered the answer. I think most of the things I'm thinking of with this finish are first cast (sandcast probably) and then powder coated, then machined. if this is the case, the texture would be a byproduct of the cast... and maybe reproduceable with sand texture in the paint. any other thoughts?
Exactly. All SURFACE COATINGS are just that, surface coatings. If you machine the part after applying the coating it will just come off with the material you are removing and expose uncoated layers of material underneath. Black Oxide coatings, Anodizing, and Alodining are also surface coatings. But i didn't mention them because they didn't match your described texture.
correction of hyperlink I guess I think I know what you mean - it is called crackle-black on these pages, sometimes referred to as wrinkle paint. Quite common on some cameras and equipment too. Looks like the machined part first gets chemical treatment to prevent it from oxidizing or otherwise changing its properties and then a coat of this paint(s). Try searching for wrinkle paint (crackle-black returns mostly different techniques) or perhaps see this page. And if you decide to test some of these techniques, keep us informed .
The old process is called "parkerized" and no, I can't get how to do it for you (I'm supposed to be sleeping, and when one does research, one tends to get sidetracked. *grin*). I've never seen that one come out anything other than a flat black. The new one that the military uses is called CARC and same as above. Any way, the finish is generally VERY hard and bonded with the underlying surface. So that's why you machine afterwards. And yes it would expose it, but usually the exposed metal is in direct contact with another piece of metal, usually with a thick layer of grease between them, and often a seal around both so oxydizing is that much of a problem. Depending on what material you are working on, it might be easier to sand blast it real lightly to get the texture and then spray a flat black over it. Hopes this helps.
speaking as a machinist generally any surface finish is done AFTER all machining is done, parkerizing is a chemical process that i've never completed my self as we do steam oxide or old school bluing. At any rate in ferrous metals you generally want to machine the metal when it's softest, as working a metal will always harden it and logicaly softer metals are easier to machine. There are exemptions as stated when you have mating surfaces that you don't want a finish coat on but that's rare and usually those parts wouldn't be chemically finished anyways. As far as how to get that look the easiest would probably the wrinkle type paints, although wasn't the W.H.O.P.R more like a anodized metal look? here's a article on parkerizing http://en.wikipedia.org/wiki/Parkerized
Mostly used now for auto restoration, here are three sources. http://www.eastwoodco.com/jump.jsp?itemID=106&itemType=PRODUCT http://www.plasti-kote.com/plastikote/auto/template.jsp?searchcode=RES&product=WrinkleFinish http://www.speco.com.au/vht_special.html Cheers
I think it's quite similar to some stuff I've seen. In any case it would accomplish the same feel I think.
