Hard Coat Anodizing

[airrj1]

I am building a set of wheel adapters to mount my Z06 rims on my Chevelle. I am interested in having them finished to prevent corrosion and oxidation. The two processes that I have found are Anodizing and Hard Anodizing (Hard Coat). I am very interested in the Hard Coat due to the very durable finish.

Does anyone know positives or negatives of either of these processes? Are there are any strength concerns with these processes? (i.e. Hydrogen Embitterment in Nickel plating) My material is 7075-T651, is this a problem with anodizing? And has anyone here had any parts Hard Coated before? I have bought many parts that are Hard Coated, but I have never had a piece coated. If I remember correctly many of the suspension parts on the Mule were Hard Coated and I am thinking that this points out that there is no loss of strength from the process, but I would like to confirm.

I am trying to contact some local shops that do Anodizing for info from them, but I was hoping to get some first hand experience from people that have had it done and not just a sales pitch from a shop. And if not, I guess I will be the guanine pig.

Thanks.

[parsonsj]

Great question. Also, for those experts, what colors are available for hardcoating?

jp

[Blown353]

I use hard anodized parts (MIL-A-8625 is the spec, Type III) a lot in my line of work (aerospace engineer.)

Type III, Class 1 anodize (hard undyed anodize) is what I usually use; the exact tint will depend mainly on the aluminum alloy being anodized, but surface finish/condition of the part, solution concentration strengths & voltages used, and time spent in the tank can also play a part. So if you have a lot of parts and want them to look like each other it's always best to process them as a batch. I personally love the typical hard anodize grey tint of 6061, so I could care less if they offered it in other colors. 6061 usually comes out the really trick looking dark gray that I love, while I know 6063 will come out kind of brownish/amber tinted. It's been a while since I've coated 2024, 7075, etc, so I can't recall their exact colors when processed via TyIII Cl1.

You can also specify Type III Class 2 (hard dyed anodize) and get the coating in various colors. I've never ordered Type III Class 2 anodized parts so I'm not sure exactly what colors are availble, you'll have to call a shop. My guess is they will all be dark colors. Standard, non-hard anodize, if undyed, comes out clear, so the sky's the limit as far as colors you can get it in. Hard anodize, even undyed, comes out dark typically, so my hunch is that the colors available for dyed hard anodized will be quite dark because of the typical dark tint of the parent, undyed process. If you want the names of some good shops I can provide some references, but they may not be cheap...

The anodize process replaces the typical oxide boundary layer found on the outside of bare aluminum and provides a more corrosion resistant coating than bare aluminum while also improving surface hardness; hard anodizing further improves surface hardness and surface lubricity (lower friction) over standard anodizing. Great for areas where there may be "sliding" kinds of wear/friction. Base metal physical properties remain unchanged, as the anodize coat is an external finish typically .001-.003 in thickness (tight tolerance parts need to have this factored in.)

Here's a link to the actual MIL spec if you want to do some reading. It's the "de facto" standard that nearly every shop out there works to. http://assist.daps.dla.mil/docimages/0000/58/77/8625F.PD6

Troy

[parsonsj]

Dark gray is exactly what I'm looking for, but most of my aluminum parts are 5052. Any idea what the "base" color is on that?

jp

[Blown353]

Dark gray is exactly what I'm looking for, but most of my aluminum parts are 5052. Any idea what the "base" color is on that?

jp

Not sure John, although my research seems to point to a bronze-black tint if you anodize on the thick side. I'd recommend calling these guys:

http://www.embee.com/

They usually do great work for me, and I just noticed they're not as expensive as I thought; $100/minimum for a batch of hard anodize, or $130/minimum for a batch of teflon hard anodize.

By the way, if you have any titanium components, if you have them Tiodized, it's a GREAT compliment to hard anodized aluminum parts...

[TonyHuntimer]

I've had smoe various parts hard anodized in black. It looks good and it's durable against the elements.

I put two images in my VB-Garage of some stuff I had hard anodized. One is an idler bracket for my Vintage Air compressor and the aluminum spacers on the the bracket. (Early design of this bracket is shown in my Pro-Touring book.)

The second image is one of the two plates I made to block the air vents in the cowl area. After I had them hard anodized black, I added some foam rubber gasket material custom cut to seal out the elements. It was a lot of work for something you will never see, but I wanted it to last...and "I" know it's there.

If you want the color to match, get all the parts coated at the same time.

The finish on the part makes a big difference in how the anodizing looks afterwards. A part that is satin will have a completely DIFFERENT look than a polished part will have after the process is done. Machined parts will look different than a raw piece of aluminum, which will also look different than a surface that has been bead blasted. If you want the finish to look the same on all the parts, make sure the finish on all the parts look the same (or close to it) before you send them to get coated. That's why polishing all the parts before anodizing them is easier to achieve a uniform finish.

If you don't care about them matching each other (for instance someone will never see the parts), then you can sometimes find a coating shop that will throw your part into somebody elses batch... just make sure they are getting the type of anodizing you want. For the guys not making a lot of money, this can save you quite a few bucks on your project.

my $.02
:)
Tony Huntimer
RaceHome.com

[parsonsj]

Good stuff all. I'm planning on having all of my stuff done at once so it matches, but the absolute color is important since I have several pieces of aluminum on the exterior and I kinda want it to match the paint.

My rear wing is 6061, my front spoiler is 5052, and my grill is made of both (welded together). I'm looking for a dark gray (or charcoal) color. Is there any chance of getting all the pieces to match given the different materials? Or should I start considering powder coating?

jp

[TonyHuntimer]

Hey John,

I'm not sure about mixed aluminum materials.... Maybe one of the other guys will be able to answer that.

Can't wait to see it in person.

Hope all is well,
Tony Huntimer
RaceHome.com

[airrj1]

Thanks for the info guys. The natural dark color would be great for me also. These wheel adapters will go behind Z06 rims that are painted dark grey. The biggest problem I think I am going to have now is finding a show locally if possible and one with a reasonable minimum order. I only have 4 small to medium size pieces.

Do you know how they usually calculate charges? By part, volume, surface area?

[Blown353]

John, my bet on your grille is that it will come out 2-tone, each alloy will have its own tint/color. It may be very minor, or it may be very noticeable, hard to say. I'd whip up a quick small sample using the same alloys/filler rod as your grille and have it processed and see if it's acceptable or not. If it's not, then I'd powdercoat/paint the thing to your liking.

[parsonsj]

353,

Good data, thanks very much. I guess I need to find my anodizing place and cozy up to them. Anybody got a mid-Atlantic (Pennsylvania/Virginia/Maryland) recommendation?

jp