Anodized Chassis

[Cliff Beer]

I've owned and restored a couple of cars with aluminum body work. I can tell you that aluminum oxidizes just like steel, and it's just as prone to rot. It needs to be shielded from the elements in the same way.

Our GT40s are rarely used in the same way as a typical road car, many folks wouldn't take out their GT40 in the rain for example, which is probably a smart move all things considered. I tend to drive my sports cars, even in the rain, and make lots of short trips around town. HomeDepot is a common run. Given that, I had to have some corrosion protection/resistence and that's why I bought a CAV in the end (stainless chassis). I suspect a steel or aluminum chassis would have been equally as good (in some ways perhaps better) provided the surface was adequately protected from the elements.

Powder coating seems to be catching on with the body-on-frame crowd wherein the chassis is fully powder coated. After having some parts of my GT40 powder coated, I'm very impressed with the toughness of powder coat. It's very durable and highly resistant to scratching or chipping. I would definitely get a steel or aluminum GT40 chassis powder coated before bolting the components on.

As far as fasteners, anywhere you don't need a high strength bolt stainless works pretty well. Stainless can gall pretty easily, so, anti-seize is a necessary thing to use. Obviously, suspension components, CV axle bolts, head bolts, etc. should all be high strength bolts, either Grade 8 or 10.9/12.9. I've looked and looked and it's difficult to find 10.9/12.9 metric bolts which have been plated. The vast majority are just black oxide finish, and this tends to rust over time, which is a drag. If anyone knows of a good supplier of plated 10.9/12.9 metric fasteners I would love to hear about it!

 

[Fred W Ballinger]

it's difficult to find 10.9/12.9 metric bolts which have been plated.

I just get the black items coated. Plating shots can do it. Dummy build the car using your stock of black bolts, sometimes you may have to shorten some, and then send a bucket full out to be plated.

If you shorten a plated bolt the cut end will rust.

Cheers

Fred W B

 

[Doc Kaler]

Just remember that plating will add material to the threads, etc....

 

[Doc Todd]

I have family that owns a sandblasting and powdercoating operation here in OKC and I am planning on powdercoating the chassis after everything is set up. Yes, it will be a drag to disassemble the entire car and put it back together but I want to try and protect it as much as possible. Right now I am leaning toward a clear powdercoat.

 

[Jim T]

I have family that owns a sandblasting and powdercoating operation here in OKC and I am planning on powdercoating the chassis after everything is set up. Yes, it will be a drag to disassemble the entire car and put it back together but I want to try and protect it as much as possible. Right now I am leaning toward a clear powdercoat.

What do you guess it will cost to powercoat the entire SLC tub & chassis?

Thanks,
Jim

 

[Grant S]

What you should do is find out what Chevrolet is coating the new 2013 C7 vettes with as they are 100% Alum chassis and I am pretty sure they spent millions of $$ figuring this out.

 

[Jim T]

What you should do is find out what Chevrolet is coating the new 2013 C7 vettes with as they are 100% Alum chassis and I am pretty sure they spent millions of $$ figuring this out.

That's exactly what I'm trying to do (see OP & post #6). So far I haven’t even been able to determine if Corvette is applying anything. I was hopping that someone here would know what/if anything Corvette is doing.


Jim

 

[Grant S]

Aye yes sorry I seen that too, short memory. Fran has friends at the Chevrolet plant maybe he could use he's pull to get an answer to this one I would be very interested to know too.

 

[Alex]

I was just thinking how it's funny how little things change over time - when I had asked this question 3yrs ago I had a bunch of people telling me how my chassis was going to rot out in 3-5yrs time if not protected, lol. Maybe I'll get a bit more concerned when my 30yr old aluminum ladder, which has sat outside 24/7 in directly sunlight, road salt, rain and snow, begins to rot :O

If anyone knows of a good supplier of plated 10.9/12.9 metric fasteners I would love to hear about it!

Fastenal

 

[Kyle]

Wow what a loaded question you all are debating. So many issues here one could write a book about the subject and still not do it justice.

Lets look at an industry that has been using Al for years and pretty much the same Grade of AL as SLC uses for there chassis. AVIATION.

Aluminum can does and will badly corrode under the right circumstances.

I am only going to cover some very basic ideas here and some of my descriptions might be slightly skewed just for ease of understanding.


Have you guys ever seen a corroded Audi, Landrover or Corvette. I have, especially Landrovers that have seen some dirt and water.

Landrovers are particularly bad where they join body panels with dis-similar metal fasteners or Aluminum to other metals.


That process is called Galvanic reactivity. There is a table that list metals in order of there reactivity and biggest note is metals on opposite ends of the spectrum do not like each other. Here is that list --> Galvanic series
Great Idea to Bookmark that list.


Topic # 2
Hey what does Corvette do, just copy that.
These larger auto makers can tap into resources, materials and systems of application that are not available to many other business in many instances. There are tried and true methods of protecting aluminum that are available to the public. Here is an example of only one of them. --> Poly-Fiber Aircraft Coatings

In short, Yes Corvette is treating the Aluminum chassis and likely al the other parts too.




Trivia tid Bit Factoid... WD40 is not WD40 no more. Its is at least WD41 now. Several years ago WD40 was reformulated to make it less flammable (Which really sucks). The old version was also really corrosive to aluminum; but now that is not really so. To prove that point if you have a real old can around; wipe a bare piece of aluminum with a white cloth soaked in the old version. Do the same with the new version. The old version will strip the oxide Aluminum forms on its exterior and newly exposed Al; the new version will not really do that. Evident in the black mess that will be on the white rag of the old WD formula.


Topic 3
Anodizing the whole chassis. Would be nice in some ways but consider the logistics of it as stated in Doc's post (#4). He does cover the basics of the process.
ALSO!!!!!!!!! do you understand the ramifications of Aluminum embrittlement as a result of coating Al with certain materials, or the fatigue strength degradation that results from coating Al with a super hard coating like some anodizing materials are. Unless you understand this I say "Don't do it" Here are some basic Aluminum factoids but this guys books are a not worth the cash he wants for them. --> Anodizing World


Random point
Comparing your old ladder to the SLC car chassis is like saying an aluminum pot is the same as an Al tennis racket. There are numerous different types, grades and Aluminum alloys out there. They are not all the same.

Point 4
I hate rust or any corrosion. I will not put up with it in any form.

Post #15 states that coating fasteners or parts in general are not as strong as the black oxide parts. The process of coating weakens the part being coated. OK that can be true, BUT do you think the makers of strong fasteners or rod ends coat there parts to just not have them meet a spec that is a standardized number amount. Same part, same size, just as strong or even stronger. Yes coating parts can weaken something if it is not done properly. The process is called Hydrogen Embrittlement. You can read some basics about it here. http://www.moldmakingtechnology.com...ment-how-small-details-can-have-large-effects

Fran At SLC does not use the black oxide parts because they are stronger, he uses them because they are cheaper!!! The customer has the option to upgrade to the better coated parts for more money if he wants to.

Cutting bolts then just sending them out to be re-coated from one of these by the bucket full plating places. All the properties that were engineered into the bolt are now likely out the window. If you want bolts with better lengths; with the correct shank length then with the right amount of threaded length after that then buy aircraft hardware. They are better but they do cost more.

It was also said that stainless steel is weaker. WRONG!!!!!!!!!! ARP makes some of the strongest fasteners in the world out of what???? You got it, stainless. You can buy stainless bolts in many of the same grades as the steel ones.

Note
A higher # grade of fastener does not make the fastener better. A grade is set of standardized conditions to be met. Different grades for different applications. Example would I want a very strong hard bolt for the bash plate on my ATV... NOPE it would just break or fracture whet hit. Would I want a soft stretchy elastic heat bolt... Nope again.

OK I hope this helps some of you guys make a better informed decision without being to over the top.

Cheers
Kyle

 

[Alex]

Random point
Comparing your old ladder to the SLC car chassis is like saying an aluminum pot is the same as an Al tennis racket. There are numerous different types, grades and Aluminum alloys out there. They are not all the same.

Fair enough; I've got some 6061 (same as the chassis) sitting outside at my pond, in constant contact 24/7 with moisture/water/snow/etc.....; other than usual wear it's not corroding or rotting.

I'll check back in 10yrs and let ya'll know if my chassis has rotted through

 

[Greg]

Powder coating aluminum also creates potential problems. If you are baking the aluminum, you are potentially ruining its "temper." All of the aluminum alloys are made using a specific process of annealing, cooling and aging in order to meet the ASTM and AA standards. This is all done in order to get the internal crystalline grain structure of the aluminum alloy to be just so. By reheating the aluminum, you are effectively ruining the work that went into it when it was created. While the aluminum may appear to be okay, once the temperature reaches a certain point, things inside begin to start moving. It may not be the aluminum itself causing the problem, but the metals it is alloyed with. Aluminum has an approximate melting temperature of 660C, but Zinc (often found in aluminum alloys) for instance has a melting temperature of only 420C. However, the material will be changing before it even gets to the melting point.

The point is, if you're going to consider something like powder coating, you need to understand the limits of the material you're using. The different aluminum alloys will all react differently to heat so it's important to understand the limitations of the specific alloy you are using, hence the reason there are so many different alloys with different chemical compositions.

I'm not saying it can't be done, just to use caution.

 

[Mick Ridley]

Im building an aluminium riveted and bonded chassis for my GT 40 From 6082 T6, which has excelent corrosion resistance. The main reason Im useing Aluminium is to build a light-weight chasis. The second reason Im useing aluminium, is I wont have to paint it

Im useing 16 swg sheet, and 10 swg extrusions. it will be bonded with Permabond ES 550, a single part adhesive, that needs to be at 130 degrees for 45 mins to cure. The ES 550 can withstand higher temperatures for brief periods, such as paint baking

At work we have extrusion made from 6082, it comes to us in the T4 temper, it is bent into shape on a mandrel bender, and then welded. It then goes in the oven for 8 hours at 180 degrees to take it up to the T6 temper. The oven is turned off, and the aluminium is allowed to cool down

If I was to powder coat the chassis providing the temperature didnt go above 180 degrees then it shouldnt effect the properties of the 6082 T6, but as was said in the previous post, different aluminuims have different properties and you need to understand the limitations of the alloy you are using..... 6082 T6, and 6061 T6 have very similar machanical properties

 

[Doc Todd]

What do you guess it will cost to powercoat the entire SLC tub & chassis?

Thanks,
Jim

Jim, I am not positive but I don't think they charge too much if it is a color they have in stock. I had him powdercoat an outside chair and he had a customer come in that wanted a chassis coated and it was maybe $100 plus material. The customer did all the prep himself and only wanted it coated. I will call this week and ask for sure though.
They are a fairly busy shop and do a fair amount of car stuff on the side as there is a hotrod shop around the corner doing 1000+ hp drag cars.

*If I want mine done in a non-stocked color then I will have to buy a box of the color and some of them reportedly cost upto $500/box.

EDIT: just read the two posts above regarding powdercoating, thanks for the info.

 

[Doc Todd]

Of course, I may just do what Tom did:http://www.gt40s.com/forum/gt40-build-logs/24525-toms-rcr-40-trackracer-18.html#post285630

He also had suspension parts anodized. Getting these smaller pieces anodized probably isn't a big deal

 

[Bill]

This coating is well worth consideration....

Nyalic - polymer resin coating that provides surface protection for years. Ultraviolet protection | corrosion protection | clear surface protection | protective coating

Easily applied, recoated, repaired and up to 10years protection for aluminium surfaces in a marine enviroment. Also can be used as a primer with superior adhesion to epoxy primers.

 

[Kyle]

Fair enough; I've got some 6061 (same as the chassis) sitting outside at my pond, in constant contact 24/7 with moisture/water/snow/etc.....; other than usual wear it's not corroding or rotting.

I'll check back in 10yrs and let ya'll know if my chassis has rotted through

I to prefer the SLC chassis for its material build list but I am not ignorant to what it takes to have a corrosion moment. We have a history of aluminum cars corroding and airplanes made out of the exact same material as the SLC dropping from the sky due to corrosion. But yes 6061 was designed to be very corrosion resistant.

I do not think you will ever see a car fail dramatically or rot right through but I do think you will see issues of some sort sooner or later; after all it is only an imperfect machine. Issues like the threaded holes, one drills into the frame, falling apart due to corrosion. Electrical issues if you are grounded into the frame.

Don't worry Alex I know you wear a large S on the front of all your shirts.

 

[Fran Hall RCR]

Steel rusts, carbon delams and splinters , aluminum corrodes...just as well everything on the planet fails ...at least its a level playing field..:thumbsup:

One thing about anodising the chassis is that due to the welds being of a differing porosity than the base metal, they can/will be a different colour when anodised...

 

[Tom]

Make everything out of 6/4 Ti, corrosion problems solved!

Should be about as cheap as a ground-based SR-71.

 

[Fran Hall RCR]

Finally a solution...thanks Tom, I will get right on it.....:laugh: