Protecting Alum. Monocoque Tub

[Howard Jones]

I have a question on powdercoating. I am told that the process involves baking the aluminum part at a rather moderate temp of a few hundred degrees. If this is correct does that sort of temp cause any strength issues with heat treated aluminum.

The reason I ask is I seam to remember that a treated aluminum such as T6 will "go soft" at something like 400F. I would hate to see some one's wonderful RCR MONO AFUed by a power coater who didn't understand the issue.

If I am wrong about this, then fine, I am sure that someone who has real engineering knowledge will quickly chime in on this. Just that I have wondered about power coating aluminum wheels and damaging them with too much heat.

How much is too much as it relates to this issue? What questions should we ask the powdercoater when we drop off parts. I would think that I would want to know the max temp of the oven and how accurate his temp controls are at least. What else?

[John W]

It deends on how th powder coating is applied. If it is dipped as are smaller parts, then yes they get cooked pretty well.

If however it is electrostatically sprayed, it is more akin to being placed in a spray booth oven to melt/cure.
I've had some parts with integral ball joints coated before and the grease and rubber boots were just fine afterwards.

[FRPGUY]

There is another type of anodizing that is pretty hard to beat called "Sanford Hardcoat" I used to make rowing shells with extuded aluminum parts used in the rigging. Extruded aluminum is prone to intergranular corrosion and this hard coat process fixed the proplem. I believe it has a "file hardness" or "case hardened steel hardness". I used a black color, but I think they might have other colors now. This stuff is almost impossible to put a scratch into it and it's not cheap! Check it out; www.sanfordprocess.com

[Rob]

Hey guys....Time for an update from my 07-26-06 posting earlier in this string. Well... much to my wife's pleasure I have removed the aluminum test panel from our back deck. It has been sitting there now since April. Bottom line: There is no visible difference between the three sections of the panel.

Once again, details: 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.

I am sold......do nothing and enjoy that sexy aloooominium!!!

Rob

[Pat Buckley]

I wonder if that is anything like Alodine? I highly toxic substance that Carrol Smith recommended in one of his books to protect bare aluminum.

I bought a gallon from Aircraft Spruce - have yet to try it. I was advised to really avoid getting it on my skin.

[Rob]

Pat the real concern with the RCR aloooominium chassis is that it gets UNDER your skin :-).
I gotta admit I like going out in the garage just to look at it.

[Scott Calabro]

Here's what an aircraft mechanic (A&P / IA), would do......
1. Decide what weather and what elements the car will be subject to.
2. Find out exactly what aluminum alloy and heat treat the tub is fabricated from, and if its been stress relieved after fabrication, as this info. will help determine what parts of the chassis need the most attention.
3. If you constantly operate the car within 0-15 mile distance from salt water, i.e. the left or right coast, at a minimum wash the car with fresh water frequently to get the salt residue off the bare aluminum. Especially in hot and humid climates.
4. Don't install a liquid cell lead acid battery, unless its in its own sealed and vented box, use a sealed gell cell. If you must use a lead acid, coat the batt box with "PAR-AL-KETONE" or similar corrosion protection.
5. Disconnect the batt. after each use, so all the chassis parts are the same electrical potential.
6. If not done from the mfg. shot peen suspension pickup points and prime with zinc chromate then topcoat with 2 part epoxy paint (Alumigrip,Jet Glow, Imron)
7. Coat all dissimilar metal contact points, where steel and aluminum are in contact with each other.
8. Fill a tumbler 1/2 full with "Knob Creek", sit back and enjoy Fran's masterpiece.

[Rob]

Well said!

[Kevin]

I agree also, "well said". Sounds like I would just leave it alone and clean it as needed.