Anodized Gun Parts Fading

[Kev Williams]

I've engraved hard anodized aluminum for years, I've never had any of the etching change color. It can be finicky to etch if the anodizing is too light, because too much laser can burn it away to the bare metal just like normal anodizing.

The gun parts are a mystery. Could they be ceracoated? I've tool engraved ceracoated AR lowers, but I've yet to ever laser ceracoat...

[Scott Shepherd]

I've engraved hard anodized aluminum for years, I've never had any of the etching change color.

You sure if was true hard coat? I've hit hard coat anodized with 75W and done nothing to it. Not even a mark. True hard anodizing is VERY hard.

[Chris DeGerolamo]

I engrave AA firearm components, never heard of this happening. I would be weary of the anodizing. PM sent.

[Kev Williams]

So the anodizing shops around here tell me! Or their customers who bring their parts in. I know that tool engraving the hard anodized parts I've done is noticeable harder on the carbide tools. There may be a 'harder' hard anodizing I'm not aware of, would be interesting to see some!

I do have a customer who brings me these small anodized parts, ironically enough they just dropped off a half dozen of them just 10 minutes ago which reminded me-- They're jet black, and sometimes- not always, but sometimes, if I hit them with my normal power, they turn no lighter than a dark blue you can barely see. And once that happens, there's no going back. Experimenting once with them I found that I have to hit them with very little power, like 15%, which barely shows up on normal anodizing. The light pass turns them a medium light gray, that's fine with the customer. But if I hit the same part with more power to see if it'll lighten it, instead it darkens it. It could be these are hard anodized, differently than what I'm used to? I don't know, and my customer doesn't know because THEIR customer has them made first.

[Robert Walters]

FWIW, I googled "UV sensitive anodizing"...

"...Care must be taken as these finishes are more sensitive to UV fade."

http://chicometalfinishing.com/anodize.asp

[Dave Demaree]

Just a lurker here as I'm not a laser owner (yet), but I do anodize regularly (Type II, not hardcoat). Let's assume this gun was Type II anodized to a thickness of 1 mil. When you laser the part surface, I'm assuming you're only bleaching the upper portion of the anodic layer, as opposed to actually "engraving" down into the pore structure. If I'm mistaken here, my apologies.

That said, I can think of only two scenarios where a bleached surface could darken back to the original anodized color.

1. The anodic porous structure is in poor condition due to dissolution or other reasons, causing the pores to not fully close during the sealing phase. As a result, the dye is slowly leaching out, darkening the bleached areas in the process. However, when this happens, the part normally has issues accepting the dye at all, as the pores will either be too small or too large.

2. The parts weren't properly sealed, again causing the dye to leach out of the pore structure.

A part that hasn't been sealed properly, or that has a poorly formed anodic layer, will often feel fuzzy or sticky to the touch. Do you notice that with the gun?

Like Scott noted, technically what your experiencing isn't possible, but if the laser is not bleaching through the entire thickness of the anodic layer, and you're dealing with a leaching problem, I can see where something like this could happen.

[Ron Fairbanks]

Have you talked to the anodizer? I have a great relationship with one of the houses in town and we know what each other needs to do a "good" job. We swap business back and forth all the time and having the relationship helps the customer get what they need without the need to blame each other for the engraving being not up to standards. And with anodized finishes being permeable, I tell all my customer that if the engraving "fades" to wipe the engraved (marked) portion with denatured alcohol which brings up and out any oils or protectants (which are not needed on anodized parts). So far this has worked great.

[Michael Hunter]

If it is oil/dirt getting into the engraving and darkening it then the following might help :

Putting the parts in boiling water for 5 to 10 minutes (after engraving) will (at least partially*) re-seal the anodising and so deter oil etc. from getting in.

* Depends on how much damage the laser has done to the structure of the anodised layer : if only just enough power was used to burn out the dye, then the re-sealing should be quite effective.

[Dan Hintz]

1. The anodic porous structure is in poor condition due to dissolution or other reasons, causing the pores to not fully close during the sealing phase. As a result, the dye is slowly leaching out, darkening the bleached areas in the process. However, when this happens, the part normally has issues accepting the dye at all, as the pores will either be too small or too large.

2. The parts weren't properly sealed, again causing the dye to leach out of the pore structure.

These have an air of reasonableness on the surface (no pun intended), but dye doesn't migrate like that... it's not in an aqueous solution once dried, so hanging out in a UV-rich environment can't be a migration factor. On top of that, even if the dye was still "wet", it would stain from the outside of the mark inward and show a very obvious migration pattern. Even poorly sealed...

[Tim Bateson]

Problem seems to be resolved. Talked with both my customer & other contractor that does the anodization. They have been experimenting with a new harder type of anodization. Of-course, I'm last to know. The solution seems to be more power. My early tests have shown revised settings of 600DPI/50S/100P is working, but more testing to come. Other hard anodized parts such as AR-15 Receivers are easily done at 400DPI/90S/90P, often even 300DPI/100S/75P.

As some have speculated, I was only bleaching a very micro thin upper layer. It didn't look any different, but wasn't enough. After a few days it was still visible, but not bright white anymore. This is not your smooth shiny or smooth semi-shiny anodization you see on most gun parts, but a matte almost light absorbing surface.

Thanks for all of the advice and contacts that were sent. This really is a great community.

[Dan Hintz]

Glad you got it sorted, Tim...

[Tim Bateson]

Update.... The change in the anodization process was not authorized by my customer or to their spec. My customer will today fire the company that did the anodization. This, I found out was the last straw in a long list of many issue the two were having. They found a company that can produce clean, crisp camouflage anodization. Sounds like a cool process. Can't wait to get the first ones in.

[Mike Audleman]

Update.... The change in the anodization process was not authorized by my customer or to their spec. My customer will today fire the company that did the anodization. This, I found out was the last straw in a long list of many issue the two were having. They found a company that can produce clean, crisp camouflage anodization. Sounds like a cool process. Can't wait to get the first ones in.

Post picts if you can. Would love to see the camo anodication.

[Kev Williams]

I want to see too. Very time intensive, not going to be cheap...