Why powder coat aluminum panels?

[RoadRacer]

I'm curious why so many powder coat the panels - is it just a cosmetic thing? On cars I've built in the past, I've left the aluminum raw, and although it got some patina, it never looked bad or corroded horribly. I put 60,000 miles on one car and never had a problem with the raw panels. But here nowadays I see a lot of coatings, so I'm curious.

I haven't ordered yet, nor seen any FF in the flesh, so I wonder if the panel material is thinner than I used before. Does anyone know what gauge and grade it is?

Thanks

[edwardb]

It's .040 inch thick 6061 aluminum. Been the same since I've been around it. It's primarily an appearance question. What do you want to see under the hood, under the car, etc.? Bare aluminum that will patina and stain over time or the color of your choice? Strictly a personal decision. The only exception might be if you live near the ocean or some other corrosive environment. Then the aluminum needs some protection of some kind.

Powder coating isn't the only choice although it might be the most popular. Don't have data for that though. Some paint. Some use finishing products like Sharkhide. Some polish. I've seen discussions about anodize, but I personally haven't seen it. I'm sure there are others.

I'm in the powder coat camp. I like how it looks new and it stays the same for years. But that's my personal choice. Not everyone's obviously. There is no right or wrong here.

[2FAST4U]

Im leaving mine raw so it can "age"

[mikeinatlanta]

I'm painting. See no advantage to powder over paint.

[Niagara Dave]

From what I understand from the guy I used for powdercoationg is that powdercoaction aluminum is difficult because it tend to warp from the heat. I would investigate this first.

[edwardb]

From what I understand from the guy I used for powdercoationg is that powdercoaction aluminum is difficult because it tend to warp from the heat. I would investigate this first.

Not in my experience. Three builds with full powder coat from three different suppliers. No change to the aluminum at all.

[erlihemi]

I like to clear coat it. Satin for "raw", gloss for shiny. I don't like aluminum patina or white holes in my foot box. As for warping after powder coating that's usually due to formed pieces being stressed.

[NAZ]

I've been welding on aluminum and other metals for more than 40-years. Of all the common metals used in construction of hot rods and race cars, aluminum is about the least likely to warp from applying heat. Stainless steel is the worst for warping. As far as heat goes, the biggest concern with the heat treated aluminum alloys is hitting that temp / exposure duration point that reduces the strength.

[NAZ]

If you like the look of aluminum consider Sharkhide. It's a product that you wipe on rather than spray and it drys almost instantly, is clear and protects all metals. I've used it on polished aluminum as you don't need to scuff the surface to make it adhere. I've had better luck with Sharkhide protecting items that are exposed to the weather than clear coats. Some of the clears flake, become cloudy, or yellow when exposed to sunlight over time.

[PeteMeindl]

This thread hasn't been active for a while but i was wondering about this exact question and stumbled upon the thread - this answered it perfectly - thanks a lot, guys!

[Fixit]

Here's my .02 about the aluminum panels...

A few weeks ago when it was really hot & humid I was working on #9365 - and sweating... and dripping. Didn't think about it.
Had to go make money for a few days, and when I got back to the car I had several ugly spots of white fur growing on the floorboard panels, and a big patch where I laid my arm down on one.

Powder coat or paint is your choice - either budget, looks, effort, whatever... but the panels really should have something on them. If just a sweat drip makes corrosion start... you be the judge.

Climate may be a factor as well.
In MN we're about as far from the ocean as you can get, but it takes about 4 heavy-duty "gully washer" rainstorms to rinse off the road salt crud & sand from the roads once it's possible to drive after winter! Once the air doesn't HURT, we want to get out and drive, but it's at your own risk for the crud on the roads

[wltrmtty]

I was looking at the Sharkhide website and it states that the metal protect lasts 3-5 years - that's not all that long. I haven't decided if I'm going with the 'natural aluminum' look or not, but will probably powder coat silver, if I do.

[Smoking Joe]

Here is the way I prep all aluminum and what I did on my 33 HR. All aluminum exposed to the outside, under floor pans, under trunk. firewall.
1. Wash and clean with dish soap and distilled water
2. Apply Aluminum Prep (I use Eastwood brand) rinse with distilled water, while aluminum is still wet apply Alodine 1201, rinse with distilled water do not let Alodine dry.
3. Apply zinc chromate, green for dark colors and yellow for lighter colors
4. Sand and apply color coat In my case I sprayed three (3) base coast (same color as body, red) followed by three (3) coats clear urethane . Color sanded and buffed the firewall.
On the inside aluminum (floor pans and trunk) I use steps 1 and 2 then applied Lizard Skin.
When look under the car and under the hood you see all aluminum matches the body color.
This is standard way to treat aluminum aircraft. My own personal aircraft is over 50 year old. I am a A&P-IA

[David Hodgkins]

I was looking at the Sharkhide website and it states that the metal protect lasts 3-5 years - that's not all that long. I haven't decided if I'm going with the 'natural aluminum' look or not, but will probably powder coat silver, if I do.

Sharkhide goes on easily, and wipes off easily with mineral spirits. I does cloud over time and is never truly "clear":

Freshly applied:


2+ years later:


That said, I use it to protect my polished panels and if I REALLY want to show off I can wipe them clean. It's not perfect, but has done a good job of protecting my panels...

[Mark Eaton]

You know, they make clear powder coats

[JL1744]

What do you think about anodizing the metal?

[cgundermann]

What do you think about anodizing the metal?

Expensive and not in the least bit durable. Looks crazy cool with some of the color choices...

Chris

[mikeinatlanta]

Problem with anodize is that the aluminum is clad. Any sanding on the panel you will have a mixture of 6061 and pure aluminum exposed. This will cause an uneven color during the anodize process. If you do anodize and are unhappy with the results you cannot go back and powder coat an anodized surface, so paint will be your only option. You also cannot repair any damage to the finish on an anodized part.

[progmgr1]

Expensive and not in the least bit durable. Looks crazy cool with some of the color choices...

Chris

There are 3 different kinds of anodizing. Per MIL-A-8625: Type I is chromic acid anodizing, Type II is sulfuric acid anodizing, and Type III is sulfuric acid hard anodizing. Type I is also called "chromate conversion coating" and is a very soft anti-corrosion coating that is mainly used as a primer coating for paint. Type II is the most widely used version. It is a relatively soft coating that stands up to solvents and cleaning agents, but can easily be damaged by a tool - hence the durability comment above. However, soft anodized surfaces can be dyed in a wide variety of colors.

The most interesting (to me) is the Type III (hard) anodizing process. The result of hard anodizing is a very hard ceramic coating that is very chemical resistant and cannot be scratched by an Xacto blade, screwdriver, etc. It's also a good electrical insulator and increases the part thickness - typically 0.002-0.004". However, IIRC, hard anodizing is only available in a few colors (black, gray) and is very difficult to rework - drill bits don't easily penetrate the surface, for example. So, I would only attempt this on parts that don't need more holes drilled. However, the idea of stone chip proof floorboards or fender liners is intriguing, to me at least...
Keith

[mikeinatlanta]

There are 3 different kinds of anodizing. Per MIL-A-8625: Type I is chromic acid anodizing, Type II is sulfuric acid anodizing, and Type III is sulfuric acid hard anodizing. Type I is also called "chromate conversion coating" and is a very soft anti-corrosion coating that is mainly used as a primer coating for paint. Type II is the most widely used version. It is a relatively soft coating that stands up to solvents and cleaning agents, but can easily be damaged by a tool - hence the durability comment above. However, soft anodized surfaces can be dyed in a wide variety of colors.

The most interesting (to me) is the Type III (hard) anodizing process. The result of hard anodizing is a very hard ceramic coating that is very chemical resistant and cannot be scratched by an Xacto blade, screwdriver, etc. It's also a good electrical insulator and increases the part thickness - typically 0.002-0.004". However, IIRC, hard anodizing is only available in a few colors (black, gray) and is very difficult to rework - drill bits don't easily penetrate the surface, for example. So, I would only attempt this on parts that don't need more holes drilled. However, the idea of stone chip proof floorboards or fender liners is intriguing, to me at least...
Keith

A few points:
Hard anodize will actually increase an .040 sheet to about .0404, so very minimal growth. Keep in mind that you are dealing with clad 6061. Hard anodize is not a great coating on the pure aluminum of a clad sheet (neither is sulfuric acid anodize). Also, although harder than bare aluminum, drill bits will still penetrate quite easily.

[FF33rod]

I thought i read that FFR uses non clad aluminum panels or did that change?

[cgundermann]

There are 3 different kinds of anodizing. Per MIL-A-8625: Type I is chromic acid anodizing, Type II is sulfuric acid anodizing, and Type III is sulfuric acid hard anodizing. Type I is also called "chromate conversion coating" and is a very soft anti-corrosion coating that is mainly used as a primer coating for paint. Type II is the most widely used version. It is a relatively soft coating that stands up to solvents and cleaning agents, but can easily be damaged by a tool - hence the durability comment above. However, soft anodized surfaces can be dyed in a wide variety of colors.

The most interesting (to me) is the Type III (hard) anodizing process. The result of hard anodizing is a very hard ceramic coating that is very chemical resistant and cannot be scratched by an Xacto blade, screwdriver, etc. It's also a good electrical insulator and increases the part thickness - typically 0.002-0.004". However, IIRC, hard anodizing is only available in a few colors (black, gray) and is very difficult to rework - drill bits don't easily penetrate the surface, for example. So, I would only attempt this on parts that don't need more holes drilled. However, the idea of stone chip proof floorboards or fender liners is intriguing, to me at least...
Keith

My generalized comment referenced the popular type 2 anodizing for the cool color palettes. Type 3 "hard" anodizing is crazy expensive compared to the already expensive colored application and you are primarily limited to black/bronze. Where you can find a vendor - usually the size of material being hard anodized is limited because of the low temp application bath. Certainly interesting and no offense meant, but for large floorboards or wheel well liners, I wouldn't recommend uber expensive mil spec aviation grade durability.

Chris

[mikeinatlanta]

I thought i read that FFR uses non clad aluminum panels or did that change?

Mine were clearly marked as clad, but I truly have no idea what they currently use, or even if they care enough to specify from their supplier. 6061 is pretty corrosion resistant so clad doesn't really do much for you, but sure messes with anodizing.

[andyw]

We're planning on powder coating the firewall aluminum panel black, but are there other panels that will be visible from either inside the cockpit, trunk, or engine compartment that will also be visible. I'm not concerned about views from under the car, but don't want to see bare aluminum from anywhere else.