Inlaying before/after hardcoat aluminum...

mitch

mitch

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Hi all-

i've been asked to help out on a special project for a special client and have given the organizers a tentative 'let me check on how doable this is' before committing.

they're building a deluxe AR-15 of some type and inquired about inlaying the various stampings/rollmarks in the aluminum lower receiver in gold, or possibly copper. i'll have the option of working before or after the hardcoat anodize is applied (probably will need to do both). my assumption is that any extra engraving & undercutting will need done prior to coating, then the inlays tapped in and shaved off flush after the coating is applied since it would cover the inlaid metals. i'm not wild about the idea of doing everything after hardcoating, so would really like to avoid that unless it's really the only way to go.

24k sounds not too bad, but copper may present difficulties as it's not much, if any, softer than the aluminum.

anybody tried this trick before? suggestions?

thanks,
mitch :tiphat:
 
SamW

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Mitch, I once worked on a frame that was to be electroless nickel plated. Undercuts for the flush gold border lines were done prior to plating. Inlaying was just fine and I shaved the gold down with brass chisels (very frequent re-shaping and sharpening). It was impossible to keep from getting very slight but noticeable gaps between the steel and the gold as I could not burnish and otherwise work the inlay as one normally would prior to metal finishing.

The reason for doing it that way was because the nickel plate will plate right over the gold. I only did that once! I suppose what you need to know is what the anodizing will or will not do to gold.
 
glstrcowboy

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if you haven't stumbled across it, finishing.com is a good resource. Might ask them if it hasn't been covered.
 
Tim Wells

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I've cut several of those already hard anodized and it tends to be chippy. I'd inlay the bare aluminum, I wouldn't even think about trying to inlay through that anodized surface. I don't know what the anodize will do to gold tough. Sulfuric acid is used in the process so you might warn them that it may not turn out right. If the gold makes it through I reckon you could clean it off after the fact and micro polish it. Post pics if you do it. Good luck.
 
R

Ron Spokovich

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The anodizing process does employ a dilute sulfuric solution in the early stages of the process. But, as aluminum weapons are anodized all the time, this shouldn't be a problem. A colorant of some kind is used, and this shouldn't be a problem, either. Bare aluminum is one thing, and aluminum oxide is another. . .once aluminum is oxidized, it may, or may not, be a problem. Do not cut after the anodizing, as, in effect, you'll be cutting into a grindstone. The 'crunch' you'll hear is the aluminum oxide chipping away, which is what some grindstones are made of. All your 'machining' should be done prior to anodizing, which will occupy the channels and undercuts you'll do. As long as not disturbed, the anodizing might not have the galvanic, negative effect on the copper you're thinking of using. Check with the experts on this, though. Gold won't react with anything (it's claimed), so there's no problem there. As long as you don't sledge your copper wire (if soft enough) into place, you may not have a problem. Your job might turn out great.
 
Leonardo

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Hi Mitch!
Usually anodizing service companies do not like to put anything other than aluminium into their baths because the problems generated by the different behavior of the metals in the galvanic process. The worst are the ferric ones. Anyway I did some works with selectively painted parts of the pieces and others with plastic inserts without any problem. So, as long as the gold will not react with the bath solution, I think that this will be the best option (I mean doing the gold inlay prior to anodizing).
What I surely would do is preparing an aluminum test plate with some gold inlay and have it anodized to see what happen. I do not think that anodizing companies see much gold in their bath so they might not have experience on this.
 
Sam

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For me, I follow my instincts when it comes to these kind of things, and I would avoid this one. Not saying you should, but I wouldn't do it. The younger and more courageous Sam probably would have taken it on, but the older and less courageous (more cowardly) Sam would not. At least not without covering myself by charging 5x the normal amount to cover additional time and hassle.
 
A

Addertooth

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There is a more complex way to do the inlay safely, After the anodizing. Purchase some Kodak KPR photocoat (if still commercially available), do reverse artwork on acetate. Coat the anodized aluminum with KPR (airbrush works great), cure, photo expose the area you want to chisel for inlay (clear acetate makes the photocoat remain, black acetate makes the photocoat wash away in the developer solutions. Bake your developed coating to re-harden it. Next, etch with sodium hydroxide (which selectively removes the anodized coating where the black was on your acetate artwork). I used to apply this method for doing detailed legends and knob tick marks on anodized control panels and it has razor sharp details. Kodak sells a solution which then strips away the last of the developed photocoat. The final step would then be to chisel/engrave the areas where the anodized finish has been removed. The removed areas will be frosty white, as versus the color of the anodized finish so they will stand out even before you engrave. Anodized finishes resist acid, but are very susceptible to bases.
I just checked, a company called transene has taken over the market, with a product called PKP, the descendant of KPR.
Link:
http://transene.com/pkp/
 
Last edited:
mitch

mitch

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Addertooth said:
There is a more complex way to do the inlay safely, After the anodizing. Purchase some Kodak KPR photocoat (if still commercially available), do reverse artwork on acetate. Coat the anodized aluminum with KPR (airbrush works great), cure, photo expose the area you want to chisel for inlay (clear acetate makes the photocoat remain, black acetate makes the photocoat wash away in the developer solutions. Bake your developed coating to re-harden it. Next, etch with sodium hydroxide (which selectively removes the anodized coating where the black was on your acetate artwork). I used to apply this method for doing detailed legends and knob tick marks on anodized control panels and it has razor sharp details. Kodak sells a solution which then strips away the last of the developed photocoat. The final step would then be to chisel/engrave the areas where the anodized finish has been removed. The removed areas will be frosty white, as versus the color of the anodized finish so they will stand out even before you engrave. Anodized finishes resist acid, but are very susceptible to bases.
I just checked, a company called transene has taken over the market, with a product called PKP, the descendant of KPR.
Link:
http://transene.com/pkp/
Click to expand...

hmmmm. kinda sounds like maybe i should contract this out to you instead...
 
mitch

mitch

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thanks to all! this project is looking more and more like a bad case of "just because it CAN be done, doesn't mean it SHOULD be done."

:thinking:
 
A

Addertooth

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Mitch,
Kind of you to offer, but I am at the negative 10 level of engraving skill at this time. I am learning the craft to support Japanese sword upgrades and restoration. My timeline for being in the market to do work for others is almost a decade away (which is when I plan on retiring from my engineering job). For now, I am learning, and if I have a suggestion based upon previous related experience, I am happy to toss it out.
 
Chujybear

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Addertooth said:
There is a more complex way to do the inlay safely, After the anodizing. Purchase some Kodak KPR photocoat (if still commercially available), do reverse artwork on acetate. Coat the anodized aluminum with KPR (airbrush works great), cure, photo expose the area you want to chisel for inlay (clear acetate makes the photocoat remain, black acetate makes the photocoat wash away in the developer solutions. Bake your developed coating to re-harden it. Next, etch with sodium hydroxide (which selectively removes the anodized coating where the black was on your acetate artwork). I used to apply this method for doing detailed legends and knob tick marks on anodized control panels and it has razor sharp details. Kodak sells a solution which then strips away the last of the developed photocoat. The final step would then be to chisel/engrave the areas where the anodized finish has been removed. The removed areas will be frosty white, as versus the color of the anodized finish so they will stand out even before you engrave. Anodized finishes resist acid, but are very susceptible to bases.
I just checked, a company called transene has taken over the market, with a product called PKP, the descendant of KPR.
Link:
http://transene.com/pkp/
Click to expand...


Would this method work also as a final step?... So engrave, excavate, inlay, annodize,.... And then follow this process to selectively remove where the gold should show through?
 
A

Addertooth

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The KPR/PKP coat is photoreactive and chemically rugged. It could be used as initially described, or placed over an engraved/inlayed area prior to the anodizing process as well, to prevent those areas from being anodized. This way they stay bright and silver. The inlayed metal will not be chemically affected by the H2SO4 acid bath used for anodizing. There are less expensive etch blocking pastes which can be applied manually, but require some art to precisely cover the areas you don't want affected.
 
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