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Anodizing 7075

Noah-01

Plastic
Joined
Sep 19, 2021
Hey all, hopefully I’m posting this in the correct area.

We have been having inconsistency with our 7075 T6 aluminum parts with both Type 2 and Type 3 anodizing. The finish is very consistent aesthetically, but it does not hold as well as it has on our 6061 parts. The finish chips easily. Our experience with Type 3 is short of hitting it with a file, the anodizing takes very well and is generally durable. This has not been the case with 7075 parts.

The part is under 10 inches tall, and under 6 inches wide. It has many sharp edges, as well as curves. The flaking typically happens close to sharp edges. We have radius’d these problematic areas in an attempt to help but the flaking still persists. It may be worth noting that on the interior of the part, it is harder to remove the finish/get it to chip.

We were told that the substrate of the 7075 is too soft to properly/easily take Type 2/3 anodizing. We had a suggestion with clear coat and then anodizing, but I would like to avoid adding extra steps, and even then I’m not sure if that will fix our problem.

Any suggestions as to how we can get this resolved?

Thank you in advance.
 

D Nelson

Stainless
Joined
Jan 7, 2015
Location
Missouri Ida
7075 is harder then 6061 all the Ar 10 and Ar 15 are 7075 forgings and they do fine
Don


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triumph406

Titanium
Joined
Sep 14, 2008
Location
ca
I've used DANCO in Santa Ana for years without issue, their the most competant anodizers I've used used,(well that was before the place in Gardena burnt down) send some parts there and see if the anodizing is more to your preference.

They do a lot of AR lowers there, so somebody likes their work.
 

Trueturning

Diamond
Joined
Jul 2, 2019
Too funny. I have seen this since the first time I ever saw anodizing decades back. It was a complaint back then too. Pay someone good money for good processing. Look for someone who knows what they are doing and keep them paid and happy. Can’t find one keep looking.

Once a new outfit does great anodize then you discuss the quality and the pricing. This should settle down frustrations. Good work often cost more is what I have found.
 

Karl_T

Cast Iron
Joined
Jun 13, 2008
Location
Dassel,MN,USA
I anodize for a hobby...

The variables here are well known. the part has to be clean CLEAN KLEEN!!!

The the bath needs to be cool and not too high amps. More amps makes it go quicker and produces heat.

So, your vendor is just getting sloppy and in a hurry.

karl
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
I anodize for a hobby...

The variables here are well known. the part has to be clean CLEAN KLEEN!!!

The the bath needs to be cool and not too high amps. More amps makes it go quicker and produces heat.

So, your vendor is just getting sloppy and in a hurry.

karl

Can you advise where one should start to get into anodize.
I ask this knowing that there are kits like the ones from Eastwood.
I'm for buying bulk chemicals and doing my own thing.

I would say that I'm not in a hurry. How about if I say that I'm an old guy without much time left ...:drink:
 

Karl_T

Cast Iron
Joined
Jun 13, 2008
Location
Dassel,MN,USA
LOTS of you tube videos.

Caswell has the best supplies, but big $. I bought a small amount of each read MSDS on each and then sourced my own. GREAT manuals from them. Older ones on the net are even better.

here's my build thread but you have to join the forum to see it:

Login
 

jz79

Stainless
Joined
Mar 21, 2017
take a very good luck at the racking points on the part, area next to them, look for soft/flaking oxide, signs of erosion due to sparking, if it is there - you need to increase the number and quality of the racking connections for that part, that is the first thing to fix, especially important for TypeIII

when there are issues with large parts near sharpish corners (usually noticed with TypeII and light dyes - areas near edges absorb more dye - look slightly darker), then increasing the ramp time (the amount of time from 0 volts till you reach the required current density for the process) can help, the idea being that sharpish corners tend to pass more current than flat areas initially (when the oxide is still very thin), and you want to avoid that, you slowly build up the oxide initially before going for full current, perhaps that is leading to the poor "adhesion" of the oxide during TypeIII process

then there is the issue with machining 7xxx alloys, I remember reading on another site a very experienced anodizing consultant talking about this - dull tools or improper speeds/feeds cause localized overheating and that leads to zinc (remember there is 6-7% of it in the 7075) precipitating near the surface, maybe longer deox bath time (and appropriate deox for 7xxx) can help with this, but it should be fixed at the machining stage, don't rely on deox bath, it isn't meant to do that
 

FredC

Titanium
Joined
Oct 29, 2010
Location
Dewees Texas
Look at your process also. We anodized 2024 for years with no problems. We used the same industrial detergent in the tumblers all those years. Then the detergent was reformulated to meet California VOC requirements even though we are in Texas and everything went to pieces. Part finish out of the tumblers, as well as adhesion of the anodizing.

A friend had something like that happen with gold plated beryllium copper parts. Heat treater blamed the plater the plater blamed the heat treater. Turned out to be the cutting oil in his Swiss machines. He changed to a nonstaining Mobilmet oil and everything became right in the world.
 








 
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