Problem anodizing blem 80% AR-15 Lower Receiver

[nil]

Back in February, Tactical Machining had a blem 80% AR15 lower for sale at $40 and it ended up coming to $55 shipped.

I milled it out, had it engraved and sent it off to be anodized.

I just got a call from my FFL that does anodizing and he told me that the blem 80% that I milled out is not able to be anodized because it's a lower quality and more impure aluminum and that it's NOT 7075-T6 aluminum as was advertised by Tactical Machining. I was told that the anodizing just isn't applying at all and that nothing's "sticking" to the lower.

My FFL told me that several went in the same batch and mine was the only one with any problems. I'm waiting on him to send me an email with pictures and a more technical description of the problem.

I've put about $200 additional into this lower for milling, engraving and anodizing and this is very distressing. I've heard nothing but good things about Tactical Machining and I hope there's something they have to say.

Has anybody had trouble anodizing their blem 80% lowers from Tactical Machining?

Update from the anodizer:

The material in the 80% we were sold (that were advertised as being 7075-T6 aluminum) is most likely 2024 aluminum, a "really cheap aluminum."

I was told this aluminum has copper as it's primary alloy agent and has very poor corrosion resistance and that it will oxidize if not cared for properly.

[sffred]

Pics?

[jpscoot_21]

I got in on that sale. I haven't yet started on it, though. Maybe someone else will chime in. I'd like to get mine type 3 anodized.

[mnichols]

Have you contacted TM about it? If so, what was their response?

[Lostsheep]

That's highly suspicious.

I doubt that it is 2024 for several reasons:

TM is a reputable company.

They get their blanks as raw forgings and I doubt the 2024 "slipped through"

The anodizer calling 2024 "cheap" is almost humorous and for me calls into question the legitamacy of their claim. 2024 (in the right temper) has a higher tensile strength than 6061 which is a common alloy for billet lowers. I do believe that 2024 is harder to anodize.

ETA: tagged to hear more about this as I am very curious.

[sactown308]

Cerak

[sactown308]

Cerakote it call it good

[nil]

Pics?

Waiting for the anodizer to send me pictures of the failed anodizing.

Have you contacted TM about it? If so, what was their response?

Sent them an email and called. Will post updates when I've spoken to them. Just wanted to see if I was the only one that noticed this.

Cerakote it call it good

Ceracoat is now my only option. The problem is these were advertised as being 7075-T6 lowers, which they may not be.

[peacedivision]

They claimed aluminum would rust? Find a new metal plating shop.

[nil]

They claimed aluminum would rust? Find a new metal plating shop.

Via Wikipedia:

Due to poor corrosion resistance, it is often clad with aluminium or Al-1Zn for protection, although this may reduce the fatigue strength.

[peacedivision]

Unless there is iron in the alloy, no rust. Aluminum can oxidize and corrode but it does NOT rust.

[Syds Grandpa]

I wouldn't call 2024 cheap. It's more expensive and stronger the 6061 t6. Some platers have issues hard annoing 2024. Quite honestly I'm more suspect of your plater then the supplier and I build a S##t load of aluminum parts.

[nil]

Just got this letter from my anodizer:

As I relayed to you earlier this afternoon, unfortunately we will not be able to provide Type III Hard Anodizing service for the lower receiver that you provided to us. We processed your unit along with 7 other parts from various customers at the same time for treatment, and your lower did not react as expected to the anodizing process, which was configured for 6061 / 7075 parts. All other items in the batch finished absolutely to spec without any issues.

The results seen in your lower are similar to what we have seen when 2024 aluminum is substituted for 7075 aluminum. While we are in fact able to anodize 2024, we have to know up front what kind of material it is and it is a more labor-intensive process. The alloy material in 2024 is approximately 4% copper, instead of the 5-6% zinc used in 7075. The tensile strength of 2024 is approximately 30,000 psi vs 7075 @ 75,000 psi, and the yield strength is around 12,000 PSI instead of 65,000 PSI. It also exhibits poor corrosion resistance. 2024 is widely used in non-firearms applications due to its ease of milling, as mill bits cut through it with ease and it has very low spalling or chipping.

Please further note that attempting to anodize 2024 aluminum in a solution meant for 7075 can lead to pitting, both visible and/or at the microscopic level. I have inspected the unit after the failed anodizing process and it displays visible marbling and some pitting, once again very consistent with 2024 aluminum. As such, we cannot guarantee nor recommend that your lower be used for integration into a firearm. While we had previously discussed Cerakoting the lower instead, I must now recommend against that option due to the condition of the lower.

We do deal with 2024 aluminum on a regular basis in the machine shop, so we are quite familiar with the material and its properties. This is why it was easy for us to identify the material even though it was represented as a 7075 alloy.

I will prepare the lower for return to you, and I will also issue you a full refund of the labor and handling charges, debiting only the cost of return postage. You have my sympathy for what is clearly a significant setback on this lower. The material difference is not a minor issue; it is a significant departure from the 7075 alloy, and has dramatically different characteristics both in end use as well as in processes such as, in this case, anodizing.

Below, please see photos of the uneven, greyish reaction to anodizing after a full bead blast and standard processing:

<picture removed>

Pretty sure my lower is scrap now.

[Mad Machinist]

Having spent a significant amount of time in TM's shop, and knowing the owner personally....I seriously doubt it is an issue with the forging........they receive forgings by the container load......and the 2024 I've machined is significantly gummier than 7075.....and at the speed they are running these I think they'd have noticed.....I'd give Jimmy a call.....if something is wrong.I'm guessing he'll do what he can to help....

[m16]

Does your receiver have a keyhole forge code?

If it does, and all of mine do, it came from Cerro Forge and they do not use "2024" aluminum.

I've anodized several, including blems and they all came out perfect.