Differences in Anodization

[Snow]

Does anybody else wonder about the claims of anodization by different manufacturers? I don't know a whole lot about the process, but it seems like there is a big variation between the anodizing of different companies, especially with Type III.

Here is where it gets touchy. I am not trying to raise yet another Fenix vs SureFire type debate, however, these are two of the companies I think have very different anodizing feels. They are also the lights I have the most experience with, so they are the examples I will use.

All of the HA on my SureFires, Novatacs, and Ra Twisty feels very thin and smooth, whereas the HA on my Fenix, Olight, and other Chinese lights feels like a thick, bumpy "shell" over the light. The SF HA feels almost like there isn't a coating at all, just a paint or something. The Chinese lights all have a similar bumpy texture and shell feeling to them. Also I've noticed the Chinese HA tends to chip off whereas the HA on my other lights tends to rub off more. I am curious about the differences here. Are they both Type III anodizing? Are they different processes? Anybody with knowledge about the process who would like to shed some light on this?

 

[Mjolnir]

Surefires like the 6p only have type II anodizing, which is not as scratch resistant.
Type III hard anodizing is quite hard to scratch. It can chip off, but it doesn't scratch off easily. The hard anodizing on my eagletac is more matte than the coating on a crappy DX light I have, which is probably type II.

 

[greenLED]

There're differences in the actual process. For example, not all HA (aka. Type III) is MILSPEC.

 

[TITAN1833]

There're differences in the actual process. For example, not all HA (aka. Type III) is MILSPEC.

What is the extra process they apply to milspec? I always thought type III was military spec :shrug:

 

[Marduke]

There is quite a bit of variation in different methods and specs
http://en.wikipedia.org/wiki/Anodizing

 

[Snow]

Another good example of the SureFire-feeling Type III is my Zebralight. If you handed me a Zebralight and told me it was a SureFire, I'd believe you. They must use extremely similar processes.

 

[xpea]

I can help here

To clarify, they are different levels of HAIII which is a generic term.
The 1st differentiation is about the quality/hardness of HAIII. This depends on process and materials used in the bath. the hardness goes from 450Hv to 550Hv. Higher is the number, higher is the scratch resistance.
Secondly, the thickness is playing a big role in coating durability. Cheap Fenix uses less than 25um coating, Chinese quality lights like Dereelight, Nitecore and Jetbeam are around 40um and SF usually uses 60um coating in their HAIII models. Of course between Fenix 25um of 450Hv and SF 60um of 550Hv, it's a huge difference in cost and durability...
Finally, the appearance is done by surface finish. More sanding you apply, more soft the touch.



PS: I'm not talking about color, which is irrelevant to the quality of anodizing

 

[Dan FO]

SureFire uses 6020 UltrAlloy aluminum which takes and holds great anodizing.

http://www.alcoa.com/gcfp/catalog/pdf/alcoa_ultralloy_6020.pdf

 

[Snow]

I can help here

To clarify, they are different levels of HAIII which is a generic term.
The 1st differentiation is about the quality/hardness of HAIII. This depends on process and materials used in the bath. the hardness goes from 450Hv to 550Hv. Higher is the number, higher is the scratch resistance.
Secondly, the thickness is playing a big role in coating durability. Cheap Fenix uses less than 25um coating, Chinese quality lights like Dereelight, Nitecore and Jetbeam are around 40um and SF usually uses 60um coating in their HAIII models. Of course between Fenix 25um of 450Hv and SF 60um of 550Hv, it's a huge difference in cost and durability...
Finally, the appearance is done by surface finish. More sanding you apply, more soft the touch.



PS: I'm not talking about color, which is irrelevant to the quality of anodizing

SureFire uses 6020 UltrAlloy aluminum which takes and holds great anodizing.

http://www.alcoa.com/gcfp/catalog/pdf/alcoa_ultralloy_6020.pdf

Wow, great information from both of you. Thanks!

 

[herrgurka]

PS: I'm not talking about color, which is irrelevant to the quality of anodizing

I had the impression that colour actually does have some relevance for the quality of anodizing, with natural HA being tougher than black or other hues. It also depends on the method used for colouring, as there a several options. I also guess that the thickness of HA doesn't really matter that much when it comes to using a flashlight in real life.

I found a good source for more information, Gray/brown and Gray/green seems to allow thicker build-ups of anodizing than other colours:

http://www.anodizing.org/Reference/reference_guide.html

 

[JCD]

I had the impression that colour actually does have some relevance for the quality of anodizing, with natural HA being tougher than black or other hues. It also depends on the method used for colouring, as there a several options. I also guess that the thickness of HA doesn't really matter that much when it comes to using a flashlight in real life.

I found a good source for more information, Gray/brown and Gray/green seems to allow thicker build-ups of anodizing than other colours:

http://www.anodizing.org/Reference/reference_guide.html

As I understand the information from that page, the "color overtones" are the resulting color of undyed anodized coatings of the various alloys listed. The maximum thickness of the coating is dependent on the alloy, not the dye color.

 

[^Gurthang]

Type II anodizing is basically done at room temperature, generally its less scratch resistant and it's porous so it can be dyed. As has been stated previously the final finish also depends on the alloy used, the chemical bath, and the finish on the part before anodizing.

Type III is done at low temperature [close to freezing] using less acid in the ano bath. The current is higher [based on surface area] and the part is anodized longer. The commercial gear also has varible power cycles, bath cooler / recycling,etc. Type III can't be dyed but the final color can be controlled to an extent by the bath, temp, etc.

There's some pretty substantial chemistry in all of this too. Different surface preps, clearing baths, de-smutting. All play a part in how the finish develops, its durability, porosity, and hardness.

 

[DM51]

Type III can't be dyed

Are you sure of that? So when SF sells a light or part as HA-BK, you are saying it is not actually HA?

 

[^Gurthang]

From what I've read, real HARD type III is so dense that the dye can't penetrate the anodite pores. There's no doubt that SF's finish is HA III. I'm certain that SF uses a proprietary method to produce a black HA III finish using special [well guarded] chemistry.

Talking to a local metal finisher I've been told that most anodizing shops have their own "secret" recipies for achieving a specific finish. Way too techinical for me to understand.

One thing I was told is that the pre-ano surface prep is crucial to achieving ano penetration, which results in better durability and wear characteristics. I take that to mean "prep time" which = $$$. Again, another reason why SF lights are more $$.

 

[DM51]

My understanding (which could be wrong) is that the dye can penetrate the pores, but that this weakens the strength to some extent and the result, while being HA, is not quite as tough as HA-Nat.

It's an interesting topic.

 

[^Gurthang]

Maybe its time to develop HA IV...

 

[JCD]

… real HARD type III is so dense that the dye can't penetrate the anodite pores.

From Anodyzing.org:

TYPE III "Hard Coating"

Color will vary from light tan to black depending on alloy and thickness. Color overtones listed below may vary with the use of additives and/or the process. Can be dyed in darker colors depending on thickness. Coating PENETRATES base metal as much as builds up on the surface. The term THICKNESS includes both the buildup and penetration. Provides very hard ceramic type coating. Abrasion resistance will vary with alloy and thickness of coating. Good dielectric properties. Corrosion resistance is good, but recommend sealing in 5% dichromate solution where increased corrosion resistance is required. Where extreme abrasion resistance is required do not seal as some softening is encountered​

.

 

[nbp]

The E01 and the Preon are both advertised as having HA and also come in a variety of colors. So it certainly is possible. Whether the hardness/durability/etc is exactly the same I don't know for sure. Probably not quite as durable, but I've been impressed with how well my orange E01 has held up on my keys. It's taken some real abuse and still looks pretty good.

 

[ElectronGuru]

Here's a reference:

.0000
.0001
.0002
.0003
.0004
.0005 < - type II
.0006
.0007 < - limit for ha light colors
.0008
.0009
.0010
.0011
.0012 < - limit for ha dark colors (other than black)
.0013
.0014
.0015
.0016
.0017
.0018
.0019
.0020 < - mil spec

​

So type II finishes are a forth (1/4) as thick as mil spec HA. Bright HA finishes are about a third (1/3) as thick.

 

[JCD]

Here's a reference:

.0000
.0001
.0002
.0003
.0004
.0005 < - type II
.0006
.0007 < - limit for ha light colors
.0008
.0009
.0010
.0011
.0012 < - limit for ha dark colors (other than black)
.0013
.0014
.0015
.0016
.0017
.0018
.0019
.0020 < - mil spec

​

So type II finishes are a forth (1/4) as thick as mil spec HA. Bright HA finishes are about a third (1/3) as thick.

A thickness of .002 inches is neither a characteristic necessary nor a characteristic sufficient to meet US military Specification MIL-A-8625F, which describes standards of the process and quality control, and covers Types I, IB, IC, II, IIB, and III anodic coatings of aluminum and aluminum alloys.

While the nominal thickness of Type III anodic coatings is known by the manufacturer, it need not be .002 in order to meet military specification standards. (Optionally, the procuring activity may use coating weight to determine if the coating meets specification. Mil-spec Types I, IB, IC, II, and IIB coatings are always measured by weight, not thickness.)

For Type III only, the nominal thickness of the anodic coating shall be .002 inches ±20% inches, "unless otherwise specified in the contract, purchase order, or applicable drawing."

That may seem like nitpicking, since .002 inches is the default thickness of Type III coatings under the specification. One must consider that MIL-A-8625F states that "Type I or IB coatings will be used unless another coating Type is specified," so Type III is not the default mil-spec coating.