Protecting Alum. Monocoque Tub

Kevin · 07-26-06, 07:34 PM

How do you guys protect the aluminum monocoque tub from oxidizing ?
I'm sure you can use a scotch brite pad but, that's a never ending task. How about using a automotive clear coat with a added flex agent or anodizing in clear ? I would hate to cover Frans (RCR) beautiful craftsmanship !

Thanks,
Kevin

Fran Hall RCR · 07-26-06, 07:41 PM

just got a batch of samples back this morning from the powder coating company......

I like the scotchbright finish with clear p/c...

I will post pics tommorow of all the experimental finishes....

Kevin · 07-26-06, 08:01 PM

That would be great Fran. I'll look forward to seeing them.
Thank you.

Kevin

Bill D · 07-26-06, 08:06 PM

I'm going to Scotch Brite my chassis, then apply an epoxy primer, followed by satin black polyurethane.

Kevin · 07-26-06, 08:24 PM

Bill- I would recomend "tinting" the epoxy primer with black so chips won't show a different color. I did not do this with my cobra and where I have stone chips, you see my yellow primer. DAM.........what was I thinking ????

Bill D · 07-26-06, 09:26 PM

Thanks for the tip Kevin

Rob · 07-26-06, 09:44 PM

Funny this topic should come up.......
I also have been wondering what to do. So, decided to first conduct a rather simple DOE. I took a sample panel divided into three equal sizes and treated one with brake clean only, another brake clean and rubbing compound and a third brake clean rubbing compound and a good coat of wax. I set the panel on my back deck on April 15th. To date I can not tell the difference between the three samples. This is leading me to the decision to do absolutely nothing to the chassis. Just leave it plain and sexy. Let's face it, the panel has seen more weather and climate fluctuations since April than the car will in it's lifetime. The only element left is salt spray, but think it highly unlikely it'll ever get driven in the winter :-)
These are my thoughts, opinions welcome.....Rob

Ron Earp · 07-26-06, 09:52 PM

Quote:

Originally Posted by VintageVenom

y. Let's face it, the panel has seen more weather and climate fluctuations since April than the car will in it's lifetime. The only element left is salt spray, but think it highly unlikely it'll ever get driven in the winter :-)
These are my thoughts, opinions welcome.....Rob

I'm with you 100%. The car won't see bad climates, and if it does, well, it's basically a race car and that's that. Kudos to those that will and want to do all that chassis prep, painting, etc, but the bare aluminum is sexy. And lighter. And if I'm lighter I go faster.........than those guys with all that paint and coating!

Rottie · 07-26-06, 10:32 PM

If the tub is all alluminum without and steel at all (rivets, etc) you can have the tub anodized which will protect the alluminum from the elements. Anodized alluminum is used through out the aircraft industry.

Alex Hirsbrunner · 07-26-06, 11:09 PM

I'll be leaving mine bare. I like the way it looks either way, but mine won't be seeing any poor weather, and I just don't have the time (or space!).

A long time ago I was told in a materials engineering class that any defect in a paint film over aluminum greatly increase the galvanic corrosion rate at the point of damage as compared to an uncoated aluminum surface. This was a common problem with the less durable coatings used on OEM aluminum wheels that were machined and clearcoated in the late 80's & 90's. Today's clears are much better, but not perfect.

I seem to recall a formula indicating the corrosion rate increase (over a bare panel) was k * coated area/damaged area (I don't recall k, but I believe it was not insignificant).

The other visual problem specific to clear paint films on aluminum is that the film tends to debond around the areas of stone damage and leaves nastly looking white halos and trails under the clear especially if they are in a moist environment - I don't believe this is the case with anodizing.

If someone asked me to do it, I would select a mechanically tough coating (like black epoxy primer) and a similarly tough topcoat of your choice. Many mfgs protect lower panels with a durable (but mostly opaque) sprayable/topcoatable PVC based coating that is generally referred to as "gravel-guard" that can be purchase at most auto paint supply stores. SEM makes a popular version of this (http://www.sem.ws/product.php?product_id=143). All in all, clear coats are at distinct disadvantage as most ingredients used to improve impact resistance are not clear by nature.

Regards,

Al

Dutton · 07-26-06, 11:37 PM

What an excellent thread!

Like many of you, I've also given some serious thought to the RCR chassis and what my move will be when the car finally arrives.

Watching what Ron, Jonathan and Bill have done/are doing hasn't made the decision as to chassis finish arrive any faster! The fabulous job each of them have done in documenting their build has been a tremendous benefit to the GT community generally, and future RCR owners specifically.

As for the challenges a finish presents, I well remember working my fingers to the bone some years ago when the factory clear-coat applied to the wheels on a former Corvette suffered the to-be-expected road rash from gravel and such. White spots here, hazy areas there - what a project it was to bring them to a presentable condition.

While bare aluminum is just plain hot, like Ron mentioned, for me it's those welds that get me going... hey, Fran, ship me that car!

Mark Worthington · 07-26-06, 11:57 PM

I had some of my Al panels powder coated, and I really like how they came out. I hit each surface with a random orbital sander fitted with a scotchbrite pad before I dropped them off for finishing. I only did the panels that would be visible when the car is done, but even at that, I calculated I added something like 10 pounds. I wouldn't think of powder coating an RCR tub. Too much surface area, coating too heavy, too expensive.

diecast18 · 07-27-06, 12:47 AM

Does anyone know what it would cost to anodize a mono chassis?

Pantera1889 · 07-27-06, 12:58 AM

Quote:

Originally Posted by diecast18

Does anyone know what it would cost to anodize a mono chassis?

It's fairly cheap.The problem is finding a shop with a tank big enough to do the entire chassis at once.

Scott · 07-27-06, 02:01 AM

I left the body of my Cobra in bare aluminum with a brushed finish. Easy to maintain with nothing but windex and the occassional soap/water. If it gets real nasty a little maroon scotch brite perks it right up.

Now if I can just get someone to buy the thing I'll order an RCR40 and probably coat the bottom with a bedliner material to cut down on the road and gravel noise.

Sandy · 07-27-06, 02:02 AM

I have been giving this some thought too, mostly swaying to doing nothing to the bare aluminum. Then I saw the Lizardskin ceremic which might have some use but I would like to know what it's like before gettting 2 gals of it. The finish of the Aluminum is very durable as manufactured since the surfaces are worked from the rollers at manufacture time. The weld area is my guess as to the least protected.

I'll bet if Rob did the test on sanded sheet the test might have been different. I have a Herb Adam VSE cobra that uses basically the same aluminum construction as the RCR 40 and it has been in and out of my garage for about 6 years with not much change. Hauled it back in the rain, etc.

Do nothing, clean and do a Lemon Fresh Pledge treatment.

A couple of thoughts, I had was some of the aircraft (yellow and green) primers that you can get in Epoxy, Zinc Chromate, and the more human friendly Zinc oxide. And no likely leave as the top cote. Aircraft Spruce has them, not inexpensive, but durable looking stuff.

Lizardskin if not a thick bed liner like material. The ceremic version seems to be safe for high temps as well as 'Class A Flame resistant' (not sure what that means). This might have some heat proofing value, but can't find much on the web other then some testimonials that were on their site so they can be somewhat discounted. Looks pretty good, would be nice to get a pint and give it a try. Will see how it works out on Jonathan's car. Looks pretty good. Some interesting comments on the Factory 5 list, but still not too much. It is easy to get as Summit Racing has it and the gun now on the site.

Lastly Zolatone, they have some nice coatings but lots of work and no info on temp capability. Might be funky looking, but I have always like the speckle trunk paint

Sandy

John W · 07-27-06, 07:06 AM

I have a 1986 caterham with unfinished alloy body.
It is not polished or treated in any way, just brushed alloy panels ,as delivered from new.

I originally painted the underside with a black paint used on lorry chassis, which is slightly chip resistant.

The only area of any of the panelling that shows signs of corroding or has discoloured is a small area on the back, where I went out in the winter and did not wash it on my return

. This is entirely due to road salt spray.

I should add, I use wd40 to clean the lower engine bay area, as this seems to make it easier to wipe any dirt off.

Also, I replaced all the steel bolts used to fix the wings on into 'rivnuts' with stainless bolts and rubber wellnuts, as I found the original steel bolts started to corode, resulting in the rivnuts turning in the panels.

Hope that helps.

Cheers,
John.

Bill Musarra · 07-27-06, 07:10 AM

Has anyone investigated this stuff. Have heard about it for years, but not anyones experiences.

http://www.zoops.com/zoopseal.asp

Bill

FRPGUY · 07-27-06, 09:18 AM

If Fran is using "Alcad" aluminum sheet, I wouldn't scotchbrite the surface. "Alcad" is a one thousand thickness coating of pure aluminum put on both sides of aluminum sheet to protect it by the manufacturer. Taking this off will expose the alloy under it. Some alloys don't weather well. The pure aluminum seems to take the weather better than some of the alloys used to make some of the higher strength alloys like, 6061 T6. If I remember right, you could buy aluminum sheet with or without "Alcad". I guess Fran could answer this better as to what he is using.