Aluminum finish options

Good morning gents!

As I've been looking at everyone's builds, I've seen many different ways that folks have finished their aluminum panels. Sharkhide, powder coating, plain, etc.

What have you done with your builds from the aluminum finish perspective? Part of me is intrigued with powder coating, but I'm worried about durability. What have you tried that you're happy with? I'm pretty sure that I don't want to just let the panels oxidize (although that would be good vintage racer look) but which way to go - that's the question!

Thanks!

Rob

Bob,

I used Rustoleum bedliner spray on my MK4 and would recommend staying away from ANY rattle can products for the aluminum panels. I'm now building a Coupe and will have the aluminum powder coated. I haven't decided on what color I'll go with yet but have actually considered doing a brushed finish on the aluminum and then a clear powder coat on top of that. My concerns with this approach would be avoiding any scratches in the brushed finish before the coating is applied.

Dave

Powder coat is bullet proof, it's about as tough as it gets. There is no durability issue with powder coat assuming it's been applied properly. The colors options are virtually limitless. I like some of the other options people have used but as far as durability there are no concerns from me.

The shark hide stuff I have heard great things about but has limited visual appeal IMO. For wheel wells I imagine it looks great. I have seen it in the engine bay and has a very distinctive look, but not a lot of variation.

Durability of powdercoat shouldn't concern you; it's plenty strong. I powdercoated all of my aluminum in Prismatics powder, with a slightly textured/hammertoned look and feel to it. I'd do it again.

Greg

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Ah, this is great info. I read some threads about guys being worried about scratching their powder coating - if that isn't an issue then I'm definitely going to look into it more. I have a local guy about ten minutes from me that does nice work. Thanks!!!

Rob

What has the experience been with cleaning the panels and using only Sharkhide protectant?
Long term durability? Probably a better engine bay heat reflector than a dark color powder coating.
Thanks. Opinions are valuable.
Ed

I have quite a bit of experience with metal treatments so can weigh in. The panels are 6XXX series aluminum (aluminium for Nigel) which can be treated in a number of ways.

Paint. Best to use an etching primer for adhesion. Paint is beautiful but easily chips or scratches.

Powdercoat. Very popular. Powdercoat is applied with an electrostatic gun and then baked. Just about any color imaginable is available and it's a very hard treatment. I would not say it's bulletproof, it can chip and scratch.

Sharkhide. Relatively easy to apply and protects the aluminum surface from oxidizing. Doesn't seem to really change the appearance much so the panels still look like the raw aluminum that was used in the original Cobras. I believe it needs to be reapplied periodically.

Bedliner. See Papa Dave's comments above.

Anodizing. Anodizing is an electrochemical process that creates a thick, protective, and decorative aluminum oxide layer on the metal's surface, enhancing corrosion resistance, hardness, and durability. A somewhat limited range of colors are available as well as clear. Appearance is best described as matte. Since it is a surface conversion rather than an application like paint or powdercoat it is more durable although it can still be scratched. I had my panels clear anodized.

Bright dip anodizing. When using hard aluminum alloys like 6XXX or 7XXX series bright dip is an option. Bright dip anodize is a chemical surface finishing process for aluminum that produces a highly reflective, mirror-like, and glossy appearance. Almost a candy look. https://youtu.be/HblLfh8UC2o?si=L3iB9ocTotW4PfsA

Electropolishing. This is a chemical polishing similar to bright dip except it uses phosphoric acid. 6XXX series aluminum that are electropolished have a chrome look.

I had all the panels in the engine bay powder coated and the rest of the panels were cleaned with Alumiprep and Alodined for protection against corrosion. On the road now for 8 years and 16K miles and every panel looks as good as the day they were finished.

The powder coating is a bit tougher than a painted surface. I have had my engine out once and replace the head gaskets once along with a bunch of other upgrades. Scratching the powder coating has never been an issue with the panels. The frame, on the other hand, has a few chips here and there from driving and initial delivery. I don't think that the FFR powder coating is as tough as the premium powder coating I asked for on my panels.

https://thefactoryfiveforum.com/atta...chmentid=82790

Very nice looking engine bay. I wish I had gone with something brighter as you did instead of the flat black I used.

Powder coat is great but every rivet hole has to be redrilled. Powder adds material, I used industrial hard coat anodize in clear ! 6 years now and not a spot on any panels ,cleans easy also .

Been driving for 4 yrs. I prepped my engine bay panels w/ acetone, and did rattle can primer and rustoleum hammered finish silver. No flaking or scratching that I can tell.

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Originally Posted by Bob 5.0

Powder coat is great but every rivet hole has to be redrilled. Powder adds material, I used industrial hard coat anodize in clear ! 6 years now and not a spot on any panels ,cleans easy also .

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Minor clarification. After powder coat, the holes may need to be chased. But not redrilled. Pretty big difference and takes only a minute or two per panel. If you do all your drilling with a #30 bit (.1285", recommended) they're just enough oversize that they may not need to be chased. Also, for this purpose, and any other time a hole needs to be cleared or re-sized after drilling, a reamer works great. McMaster, and others, sell them in numeric sizes. Highly recommended.

I'd say maybe 25% of my pre-drilled holes had to be chased after powdercoat. To say that every hole needs to be redrilled is quite the exaggeration.

Greg

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Originally Posted by Ejzajac

What has the experience been with cleaning the panels and using only Sharkhide protectant?
Long term durability? Probably a better engine bay heat reflector than a dark color powder coating.
Thanks. Opinions are valuable.
Ed

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I cleaned all the panels that were visible from the engine bay and coated them with Sharkhide. I was, unfortunately, not smart enough to protect the panels from fingerprints when I took delivery. I tried several aluminum cleaning products but none of them did a satisfactory job of removing the prints. I found that vinegar on paper towels remove the prints and restored the aluminum to the "mill" finish. Not really a big deal but just an extra step that could have been avoided by wearing gloves while handling the panels. I immediately then coated the panels using cotton diapers my wife ordered from Amazon. If you use Sharkhide don't worry about the streaks that appear during the application process... they disappear rather quickly as the product dries.

A cool side effect of my question is seeing some of your engine bays done up in "aluminum" powder coating (or a similar color). I had been contemplating a darker color, but boy those finishes look great! And a nice side benefit of those colors is that if I do scratch the finish, it'll be very hard to see since the base metal is almost the same color :)

Rob

Clear anodize

Attachment 219937Attachment 219938

I just bought 4 cans of the clear gloss top by Por15. Glidden also has a similar product out. I have used neither, yet, but intend to put over my orange Kabota tractor that is sun fading.
good luck,
https://www.glidden.com/products/int...coat-semigloss
https://por15.com/collections/topcoa...39607017930919
Shark hide is a product that works and used on some of my aluminum panels. It is holding up very well and does not yellow.
It will prevent transmission cases, bellhousing and etc from oxidizing as time and moisture works on the metal.

I didn't even think of treating the bellhousing and trans - thanks!

Rob

I probably did not do a through job, but the starter, IRS carrier, water pumps and all the black oxide bolts provided in the kit warrant a coating of one of the clears.
The places I coated, still look like new.

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Originally Posted by StangRacer

I cleaned all the panels that were visible from the engine bay and coated them with Sharkhide. I was, unfortunately, not smart enough to protect the panels from fingerprints when I took delivery. I tried several aluminum cleaning products but none of them did a satisfactory job of removing the prints. I found that vinegar on paper towels remove the prints and restored the aluminum to the "mill" finish. Not really a big deal but just an extra step that could have been avoided by wearing gloves while handling the panels. I immediately then coated the panels using cotton diapers my wife ordered from Amazon. If you use Sharkhide don't worry about the streaks that appear during the application process... they disappear rather quickly as the product dries.

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Thanks for the input and advice.

Since I will likely do another build, I've kept track of things that I will do differently. Panels are on the list. Next time I will do the anodize finish described by Mike Bray above, providing a highly reflective surface for radiant heat transfer (which will reject 90+% of the heat reaching the footboxes). This will be done on the footbox panels that are visible when the hood is open, as well as things like the firewall. F panels will be done also but only for a finish match. I will also Raptor the outside of the F-panels, and panel sides visible in the wheel wells and under the car.

If going with paint or powdercoat, from a heat transfer perspective, I recommend the lightest possible color in the shiniest finish you find acceptable, to provide optimal rejection of radiant heat, the primary source of heat to the footboxes. More info on the heat transfer topic here https://thefactoryfiveforum.com/show...082#post576082

PMD24, unfortunately anodized aluminum has a rather high emissivity. This means that it actually absorbs radiant heat much better than polished aluminum. The thin ceramic coating from the anodizing process, while looking shiny, has an emissivity of about 0.85.

To add a little more context, emissivity can be thought of as the percent of radiant heat that will be transferred, in this case the radiant heat from the engine and exhaust system. Bright polished aluminum has an emissivity in the range of 0.05, which will slowly degrade due to oxidation over time if not continuously polished. A heavily oxidized sheet of bare aluminum will have an emissivity in the neighborhood of 0.30. As said before, applying any anodizing to the aluminum creates a ceramic film which increases the emissivity to 0.85ish. Actually, people anodize aluminum to increase heat transfer, typically when used as a heat sink.

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Originally Posted by JJK

PMD24, unfortunately anodized aluminum has a rather high emissivity. This means that it actually absorbs radiant heat much better than polished aluminum. The thin ceramic coating from the anodizing process, while looking shiny, has an emissivity of about 0.85.

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Is that for bright dip anodizing?

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Originally Posted by egchewy79

Been driving for 4 yrs. I prepped my engine bay panels w/ acetone, and did rattle can primer and rustoleum hammered finish silver. No flaking or scratching that I can tell.

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Same here for last 3 builds.
Ralph

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Originally Posted by Mike.Bray

Is that for bright dip anodizing?

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Does not matter. We may think that because it is shiny it will reflect radiation heat transfer, but that is unfortunately not the case with any anodized product. It can be both shiny and very effective at transferring radiant heat.

FWIW, started my career as a thermal engineer for GE in the late 90s, have a MS in ME with a concentration in thermal science. I was involved in a lot of 3D modeling and simulations of heat transfer for electrical systems and had a lab to heat test prototypes for new products. I would frequently have to tell the other engineers that the color of paint was negligible for radiant heat transfer purposes in our applications. They would always argue that white paint would reflect heat and black would absorb, similar to how black objects get hotter outside than white objects. That argument works for absorptivity but not emissivity for infrared heat transfer.

I brushed my aluminum and then coated with Sharkhide. Got 2000 miles on it so far and still looks new.https://thefactoryfiveforum.com/atta...7&d=1608684904

Did you Sharkhide both sides and before putting the panels on?

I painted mine black but if I built another car I'd coat the aluminum panels with U-Pol Raptor Bedliner.

NAKED PICS
https://youtu.be/_wnHDNgnNqs

2024 UPDATE
https://youtu.be/iwslgKJUaKc

Good Luck & Happy Motoring!

Quote:

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Originally Posted by JJK

To add a little more context, emissivity can be thought of as the percent of radiant heat that will be transferred, in this case the radiant heat from the engine and exhaust system. Bright polished aluminum has an emissivity in the range of 0.05, which will slowly degrade due to oxidation over time if not continuously polished. A heavily oxidized sheet of bare aluminum will have an emissivity in the neighborhood of 0.30. As said before, applying any anodizing to the aluminum creates a ceramic film which increases the emissivity to 0.85ish. Actually, people anodize aluminum to increase heat transfer, typically when used as a heat sink.

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Thanks for pointing out the emissivity info on anodize. Wasn't aware. Did some research and confirmed. Sure make sense when you consider aluminum heat sinks. Guess I'll stick with the Mothers polish and Sharkhide.

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Originally Posted by GoDadGo

I painted mine black but if I built another car I'd coat the aluminum panels with U-Pol Raptor Bedliner.

NAKED PICS
https://youtu.be/_wnHDNgnNqs

2024 UPDATE
https://youtu.be/iwslgKJUaKc

Good Luck & Happy Motoring!

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Plan was to do a low maintenance drive anytime car that would last a long time. All most none of the engine sheetmetal shows with the Coyote stuffed in.

https://thefactoryfiveforum.com/atta...2&d=1721414949

Used black truck bed liner spray on both sides the engine compartment & all weather facing alloy sheets. Used Thermo Tec on all heat facing alloy sheets including the firewall & footboxes. Been solid over the years. The liner is easy to touch up. Do a panel check when I respray my pickups bed. Pickup FWIW is 27 years old with a good as new bed so the stuff works long term.

what process/tools did you use for preping the Al for the Sharkhide?

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Originally Posted by 2112

what process/tools did you use for preping the Al for the Sharkhide?

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After using elbow grease and vinegar to remove the fingerprints I ran warm water over the panels to make sure all the vinegar was removed. I then made sure the panels were completely dry before I applied the Sharkhide with a cotton diaper.

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Originally Posted by StangRacer

After using elbow grease and vinegar to remove the fingerprints I ran warm water over the panels to make sure all the vinegar was removed. I then made sure the panels were completely dry before I applied the Sharkhide with a cotton diaper.

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1. Do you think the preparation could be done with vinegar solution alone?
2. Did you consider other chemicals for cleaning, MEK, denatured alcolhol, or Sharkhide Prep cleaner?
3. How many coats of Sharkhide did you use?

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Originally Posted by Ejzajac

1. Do you think the preparation could be done with vinegar solution alone?
2. Did you consider other chemicals for cleaning, MEK, denatured alcolhol, or Sharkhide Prep cleaner?
3. How many coats of Sharkhide did you use?

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I used the white vinegar alone at full strength. I believe it was on this forum where I read about another member doing the same thing to remove fingerprints from the aluminum panels. Of course, how successful you are is going to depend on how badly the prints are etched into the aluminum. Mine were not too bad...

I did try an aluminum cleaner from a company called "Star Brite". IRRC, it's mainly intended for cleaning the pontoons on boats... It worked okay but not nearly as good as white vinegar... There may be something out there better, but I wanted that portion of the project completed so I just rolled with the vinegar.

I only used one coat of the Sharkhide. When I first applied the Sharkhide I was EXTREMELY disappointed. I followed the application process exactly as in the instructions from Sharkhide... I even watched a youtube video on the application process. What none of those sources mentioned is the finish will be very "streaky" until it dries. On the first panel I probably did put more than one coat on trying to get it as even as possible. The more I tried to get the streaks out the worse it looked. I finally decided to walk away for a bit and went inside and had lunch. When I came back out the streaks were completely gone and the panel looked fantastic. From there forward I just did one coat on the remaining panels.