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Van's Comment on Anodizing

gregfuess

Well Known Member
I am considering having my slow build kits commercially anodized. Based on one telephone conversation with a local shop, the cost to have the parts coated to MIL-A-8625 Cl 1 or 2 would be the same, and about $1k~2k. The most odious part of the process would be the three week turn around. I am leaning heavily in this direction.

I wanted to get Van's thoughts on anodizing their parts. When the question, "I am writing to ask whether the aluminum pieces shipped with Van's slow build empennage, wings, and fuselage and kits designed to accommodate an alodine primer?" and then rephrased to ask, "Can If Van's assure that the aluminum parts of Van's slow build kits are designed to accommodate such a primer." I was surprised to get this "no speak" response back:

"All our kits (all models, both standard and Quick Build) come with anodized wing spars and fuselage center sections.

If you intend to anodize additional parts or items, you will do so under your own discretion and responsibility."

Obviously Van's would ensure that what they anodize would be capable of the process. I am a little disappointed in the response. Any thoughts on commercial anodizing, and Van's lack of any statement regarding anodizing their parts?
 
You do realized that Alodine and Anodize are two different processes…right?

I can’t comment on Van’s response, but I will tell you that in the kits built by Sling Aircraft, 100% of their aluminum parts are Alodined at the factory, and they recommend no further priming (of interior components) is required. The Alodining is all scuffed and scrubbed off the exterior in the painting process.

Paul
 
You do realized that Alodine and Anodize are two different processes…right?

Paul

Thanks Paul, I don't have a strong appreciation of the difference, no. I chose Anodizing because that's what Van's does with a few pieces, such as the wing spar.

If there's an advantage of that Alodining over Anodizing, I would appreciate a pointer to where to learn more.
 
Alodine is a tradename for chromate conversion coating. MIL-DTL-5541. This uses chromic acid to create a film coating and does not change the dimensions of the part.

Anodizing utilizes electric current and (typically) sulfuric acid followed by a dye and seal step. This creates a hard layer on the surface, which is why it can crate fatigue issues in cyclic loaded parts. (an award winning AB helicopter was lost due to this "improvement" by the builder)

Google is your friend.
 
The kits built by Sling Aircraft, 100% of their aluminum parts are Alodined at the factory, and they recommend no further priming (of interior components) is required. The Alodining is all scuffed and scrubbed off the exterior in the painting process.
Paul

Another factor here might be that Sling kits use 6061 aluminum which is already extremely corrosive resistant.
 
Tell us why you wish to anodize everything. Being in NM, it’s a pretty dry climate so I wouldn’t expect corrosion to be a significant issue. I doubt you will ever get anyone to say go ahead and anodize whatever you want.
 
Do yourself a favor- take ONE small piece of .032 2024T3 aluminum sheet to the anodizing shop & have them do it.
When you get it home, drill a series of #30 & #40 holes in it, than dimple some of them. While you're at it, put a 90 deg bend in one end of it. You could practice rivet a bunch of those holes too.
See the spider cracks around the drilled holes? See the circular cracks around each dimple? See the large cracks along the bend? See the distinct cracking around each rivet?
This doesn't even start to address the degraded strength & brittle qualities the piece would have compared to a typical alodined/primed piece.

The kit assemblies that come anodized from the factory are specifically designed to accommodate for any negative characteristics this process instills. They probably picked the process because those assemblies demand close dimensional tolerances to fit together & used it only on those areas.
 
Seem to me like Van's response is commonly CYA. They haven't done, it so why would they authorize it?

Authorizing any modification that they haven't tested would be foolish on their part.
 
Mel;1642438 Authorizing any modification that they haven't tested would be foolish on their part.[/QUOTE said:
Except that Van's does anodize. For example, the wing spar comes golden anodized. Yet there are enough examples out there, one cited of an award winning helicopter, that didn't fly long due to inappropriate use of anodizing.

A little learning may be a dangerous thing.
 
All ribs, bulkheads, angles and stringers were anodized in my F1 kit. Skins are primed. Steel parts are plated.
 
Alodine

Early in my build process I used Alodine (1200). It is very light, is a 'conversion' coating so it doesn't flake off, and has been used in aviation for ages. Adds no measurable thickness. Prime & Paint over it if you wish (or not). All good eh?

Well the problem is that the stuff is toxic (hexavalent chromium) and very hard to properly dispose of. [no, pouring it down the toilet is not a solution]

It is a messy process... you need to rinse off the parts... so now you have contaminated rinse water as a bonus.
 
Greg, seems like you might want to back up a step and do your homework re. Anodizing vs. Alodining. The question you posed to Vans resulted in an ambiguous answer because the question didn't make much sense (to them).

I do agree with the comments regarding a wholesale Anodizing of your 2024 parts, it would be a bad idea without a serious engineering review.

Alodine on the other hand is proven in aircraft construction, with all the before mentioned issues.

No dis, just hoping to see you on the right track.

Cheers
 
…and

If you dig a bit, you will find that there have been accidents attributed to anodizing certain parts.

I have no issues with the alodine process, as has been previously stated, anodizing is a different animal and it can have unexpected and sometimes catastrophic consequences.
 
"2024 is commonly used with an anodized finish or clad form (“Alclad”) with a thin surface layer of high purity aluminum". (Aircraft Spruce)

I believe most of the 2024 aluminum used for the kit is already "Alclad" meaning it is anodized sheet... Alclad=Anodized.
 
Except that Van's does anodize. For example, the wing spar comes golden anodized. Yet there are enough examples out there, one cited of an award winning helicopter, that didn't fly long due to inappropriate use of anodizing.
A little learning may be a dangerous thing.

The question was not about the spars. It was about anodizing other parts which Van's hasn't tested!
 
Alternative?

Question: If you don't want to anodize for all the reasons given above, and you don't want to alodine due to the haz mat issue, what is the best alternative?
 
Alclad=Anodized.

Uhm, attempting to be tactful here, but NO, that is incorrect. Anodize and Alclad are two entirely different things. May I suggest going to wikipedia and looking up Alclad, Anodize, and (just to be complete here) Alodine.
 
Anodizing is an electro/chemical conversion process that fundamentally changes the outer layers of the part. It is a great way to corrosion protect aluminum. That's why Van's anodizes the spar. To give (arguably) the most critical component on the aircraft good corrosion protection.

But what anodizing gives in corrosion protection, it takes back in fatigue life and paintability.

Van's has done the work to size the spars to allow for the fatigue life issue. They haven't tested or done the analysis on the other parts, so they can't comment on what the impact would be of anodizing "other" parts.

As far as paintability, anodizing changes the texture of the surface of the part. It becomes rougher and a little "crinkly". I doubt you'd want that on any part that is going to show on the airplane - external skins for instance. You'd either have to sand off the anodized layer, apply excessive primer and paint (with associated sanding), or have an airplane with a rough texture.

Alodining, on the other hand, is a spray on/rinse off liquid (alternately, you can dunk the parts in alodine) that adds another layer of corrosion protection by chemically converting a VERY thin layer of the aluminum to a less reactive surface layer. The impact of that layer on the strength (and smoothness) of the part is either nonexistent or negligible. But it is beneficial from a corrosion standpoint.

I'd suggest that anodizing anything beyond what Van's already provides in that condition might not be advisable unless you pick and choose wisely.

And alodine? It is a carcinogen. Might want to consider using a wash primer or epoxy primer (and no alodine) if that is a concern for you.
 
Alternatives

Option 1. Find a company that does alodine. Let them do it.
Option 2. My opinion, prime with P60G2.
 
Yes, it's possible to have an anodized airframe (I have one), but it has to be designed that way, and RVs aren't.
Can't go wrong following Van's recommendations.
 
Alodine

A local company will alodine all the aluminum parts to MIL-DTL-5531 Cl 1A for all four kits for about $800~1000 delivered together. Or about the same price per kit if each kit is done separately.

My understanding reading the MIL spec is that the Class 1A coating is the best corrosion protection and requires no primer.

The biggest challenge now is to tag each piece identifying the part number.
 
I alodine most of the aluminum parts before priming. I found that the primer will adhere to the surface really well, same for epoxy/fiberglass layups.

I used the big plastic tub that is sold to mix concrete in. I filled it up with two gallons of alodine and after a minute of soaking, the parts came out yellow color. The alodine in the tub can be re-used again for many times over.
 
I alodine most of the aluminum parts before priming. I found that the primer will adhere to the surface really well, same for epoxy/fiberglass layups.

I am doing this for the interior portions of the plane, so I don't see the benefit of primer there. By the time the exterior is ready for paint, well that's a bridge I cross when I come to it.
 
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