RCR aluminum frame coating

[Pat]

What’s everyone’s thoughts about painting, powder coating, lizard skin, etc on the aluminum frame? I assume it will never be out in bad weather but do people leave it exposed, cover the bottom or do the whole thing? I like the aluminum look and would like to keep as much exposed but don’t want it to degrade over time. Looking to see what others have done.

Thanks!

 

[Neil]

Standard aircraft practice on aluminum is to use a self-etching zinc chromate primer and (optional) topcoat. The epoxy primer from Aircraft Spruce gives you a nice hard glossy yellow green finish. On my steel tube chassis, I used a yellow topcoat of an aliphatic isocyanate polyurethane. It is made for high-performance aircraft. $$$ This is not a GT40.

 

[Neil]

Weather resistance of aluminum depends on its alloy. The highest strength alloy, 7075-T6 is corrosion prone but 5052 has far better resistance to corrosion but far lower strength. Paint or bare- it's your choice.

 

[Randy V]

Personally, I prefer the Zinc Chromate and Urethane paint. A number of people have gone the powder coat route - but I’ve found that powder coating alloy really works best if you sand or otherwise put some “tooth” in the surfaces to be coated.

 

[Scott]

I also like the aluminum look. My plan is to brush the chassis and use one of the clear, air-cure Cerekote finishes specifically designed for aluminum. I also plan to coat all of the CNC parts less the brushing step because I like the machining marks.

Although i don’t have any experience with this specific finish, I’ve been very impressed with Cerekote on exhaust systems and firearms. I will also strip all of the powdercoat on the car (e.g, cage, suspension, erc.) and Cerakote it with oven-cured solid color.

 

[Rod Dittmar]

Pat, I like the look of shiny aluminum also, but after restoring a bunch of old British motorcycles, got tired of trying to figure out ways to keep it that way. So I decided to go a completely different route and used a product called POR-15 on my RCR aluminum chassis. After spraying 2 coats of Base and 2 coats of Top Coat, it came out a very nice matte black finish. I think it looks great in contrast with all the other CND'd aluminum suspension parts on the car. However, if you are still prone to shiny, you might look at a product called Sharkhide. Super easy to apply, I used this on the aluminum panels of a FFR Cobra replica that I built 8 years ago and it looks just as good today as when I first applied it.
Rod

 

[Randy V]

X2 on the SharkHide to maintain the glossy finish of polished metals. It also stands up to heat very well - although I don’t recall the spec. I did a motorcycle valve cover many years ago and it maintains its almost chrome appearance for at least a couple years afterward (I sold that bike and don’t know where it is today).. It’s not inexpensive but a little bit goes a very long ways.

 

[Brian Kissel]

I like Randy, and Rod have used the SharkHide successfully on aluminum parts.
Regards Brian

 

[Derek]

Has anyone ever considered type III hardcoat anodizing for the aluminum chassis? I'm considering this as a base layer of protection...?

 

[Neil]

Has anyone ever considered type III hardcoat anodizing for the aluminum chassis? I'm considering this as a base layer of protection...?

I doubt that you will find anyone who can do it. It requires a refrigerated tank big enough to immerse the entire chassis and enough electrical current to grow the film. Search on my Zinc Chromate posts.

 

[Derek]

I doubt that you will find anyone who can do it. It requires a refrigerated tank big enough to immerse the entire chassis and enough electrical current to grow the film. Search on my Zinc Chromate posts.

Thanks for this. I found this quote of yours;

"my advice on finishing aluminum is always the same prepare it with Scotch-Brite clean it very carefully wipe it with MEK or denatured alcohol then spray a coating of zinc chromate epoxy primer. I bought mine from aircraft spruce and it is very durable. You may not like the yellow green but it's used on aircraft everywhere and is the standard for protecting aluminum"

Thanks for this rabbit hole, very helpful advice. A follow-up question,

After the Zinc Chromate coating is applied, what do you recommend for final finish? Regular automotive primer/paint...? Or maybe powder coat?

 

[Neil]

Thanks for this. I found this quote of yours;

"my advice on finishing aluminum is always the same prepare it with Scotch-Brite clean it very carefully wipe it with MEK or denatured alcohol then spray a coating of zinc chromate epoxy primer. I bought mine from aircraft spruce and it is very durable. You may not like the yellow green but it's used on aircraft everywhere and is the standard for protecting aluminum"

Thanks for this rabbit hole, very helpful advice. A follow-up question,

After the Zinc Chromate coating is applied, what do you recommend for final finish? Regular automotive primer/paint/clear...? Or maybe powder coat?

Unless you do not like the color of zinc chromate it is not necessary to topcoat it. The epoxy primer itself is hard and glossy. If you wish to topcoat it , a n aerospace quality 2-part Polyurethane is a very good choice. I used a light orange polyurethane over the zinc chromate primer. In this photo you can see the difference in colors. Black is popular for a chassis color but I wanted a bright color.

 

[Derek]

Unless you do not like the color of zinc chromate it is not necessary to topcoat it. The epoxy primer itself is hard and glossy. If you wish to topcoat it , a n aerospace quality 2-part Polyurethane is a very good choice. I used a light orange polyurethane over the zinc chromate primer. In this photo you can see the difference in colors. Black is popular for a chassis color but I wanted a bright color.

Thanks for this. I found this compatibility chart but it says polyurethane is not a compatible topcoat when using zinc chromate primer? It says to use an enamel?

https://www.aircraftspruce.ca/catalog/pdf/PTIxref1.pdf

 

[Neil]

Thanks for this. I found this compatibility chart but it says polyurethane is not a compatible topcoat when using zinc chromate primer? It says to use an enamel?

https://www.aircraftspruce.ca/catalog/pdf/PTIxref1.pdf

That chart differentiates between a "Zinc Chromate Primer" and "Epoxy Primer", the zinc chromate primer they are referring to is the usual stuff in spray cans or equivalent. A two-part zinc chromate epoxy primer is zinc chromate in an epoxy binder. That is altogether different. This is an old outdated can of the polyurethane than I used as a topcoat over zinc chromate epoxy primer on my chassis. It was purchased in Tucson at a surplus store; this is what the US Air Force paints their jets- "aliphatic isocyanate resin". Since it is an isocyanate, you should use a respirator or apply it outdoors.. upwind. A good commercial polyurethane that I've used is the Eastwood stuff. Its application is a normal process.