Painting Aluminum

For materials such as the diamond plate used on the side of the platforms this year, what would be the best way to spray-paint them so that they maintain the same reflection from the aluminum but still has color to it? Basically, a tinted clear coat. I couldn’t find anything relevant online. Yet.

I’m not sure how well this would work on aluminum or steel, but at the TechnoKat shop last year we had a spray paint that could be used to paint clear glass. We had colors like green and red, and when sprayed on the glass it would color the class, yet keep it transparent at the same time. I remember playing with this a little bit and if you can find it and mess around with some it might stick to metal.

what your looking for it a process called anodizing. I’ve had friens who have head paintball markers done like this. Check a local paintball proshop and maybe they will donate the work. It can be expensive and you need special equipment to do it yourself.

Hope this helps

Anodizing would make the surface less “shiny”. Anodizing itself does not color parts, but is used to protect aluminum by making it’s surface harder (puts a coat of aluminum oxide on). Color can be added because anodized aluminum is more porous then normal Al (which is also why it loses some of its reflective properties). [Someone correct me if anything I said above is wrong].

You don’t need special equipment to anodize aluminum, but it involves a strong acid (the sulfuric acid that’s in your car battery would work) so it needs to be done by someone with experience (sort of like welding).

Yan, I think spray paint leaves an ok finish, isn’t that what was used on last year’s robot?

Greg

when you add color most or all the Metallic character of the aluminum lost because pigments cover the underlying surface. but if you get just a clear coat no pigment Metallic characters of the aluminum are retained. or Organic Dying you actually all Metallic character of the aluminum retained adds a high brilliance. so it is possible to keep the same brilliance of an object that is anodized

im no were near this smart i got all my information off www.anodizing.org great site with anything you would want to know about the process actually some what interesting.

Your right that the process itself does not color the metal however check this link out anodizing benifits the key section to read is **Aesthetics. ** Aesthetics. Anodizing offers a large increasing number of gloss and color alternatives and minimizes or eliminates color variations. Unlike other finishes, **anodizing allows the aluminum to maintain its metallic appearance. **

At least with anodizing you get the metallic look unlike gloss paint that will hide the textures of the surface plus paint chips anodized colors do not.

Hope this helps

For anyone that’s interested:
You ever notice how if you cut or scratch a old piece of aluminum the exposed surface is much more shiny then they outside. This is because the outside has oxidized to form Aluminum Oxide (Al2O3). This happens just like rust forms on iron. Anodizing produces a thicker layer of Aluminum Oxide faster then it would otherwise happen.

Because of this I don’t think anodized aluminum is as shiny as it is before it was anodized. Jay pointed out a great link describing the advantages of anodizing.

Personally, I think anodized aluminum looks better. Knowing Yan and his situation, I doubt he wants to try and anodize his aluminum part (well, he probably does but it most likely wont happen :wink: ). I would suggest cleaning the aluminum with rubbing alcohol then applying a coat or two of normal spray paint. It probably won’t be the most durable finish, but it’s cheaper then anodizing.

Greg
[If I’m wrong correct me]

Edit:
Here is a good link about the process of anodizing aluminum: http://www.focuser.com/atm/anodize/anodize99.html
He makes a few mistakes (mistakes a base for an acid!) but by FAR the best anodizing description I could find.

im not sure if this would work on aluminum but powder coating provides a nice transparent coat of color while keeping the metalic properties of the metal :confused:

Powder coating can add a lot of weight though.

Last time I saw a powdercoated robot, it wasnt transparent. It completely coats the surface with the powder, and you sure cant see through it.

Cory

http://team254.bcp.org/index.php?menu=current&vars=numID_23

The red and blue parts of the lower frame, subframe, and upper arm assembly are all powdercoated.

Another point of interest - the silver claw section is nickel-plated, giving it that chrome effect. Nickel plating is a form of anodizing.

GregT:

Because of this I don’t think anodized aluminum is as shiny as it is before it was anodized. Jay pointed out a great link describing the advantages of anodizing.

It depends on what process you use to get it done. There isn’t just one way to anodize everything different processes still the same anodizing effect with aluminum but leave certain characteristics or features that other will not. Organic Dying if you scroll down to were it says organic dying and look under Appearance of surface it says that the Metallic character of the aluminum retained high brilliance. so there are ways to have something anodized and still retain the metallic shine it once had.

I don’t really know much about anodizing, but if you decide to paint it, I can offer you some help.

You can’t just spraypaint metal. If you do, you’ll find that it begins to flake off after some time (a week, two… depends on how much contact the material has). This happens because the metal doesn’t really bond all that well to the paint molecules. If you want to paint metal, you first need a primer.

A primer essentially makes the metal a lot more pourous so that the paint molecules bond to it better. However, just like paint, you should sand the metal before applying the primer. Some people say you should sand the primer using fine grit sandpaper and apply a second coat before you apply the paint. You can get primer at home depot or any automotive store (Pep Boys, etc.)

With the paint, you should do atleast two coats, three coats. People recommend you again sand using fine grit sandpaper in between coats. When using spraypaint, the important thing is to do a cross-hatch pattern – a ‘coat’ consists of a very light spraying in vertical lines and very light spraying in horizontal lines afterwards. Don’t use too much, though - you get terrible results if you add too much paint in one coat. The end product comes out a lot better if you use too little paint on a coat but do several coats than if you add too much paint on one coat.

Finally, to get that shiny automotive-metalic effect, you need to buy clear-coat spray. This is exactly what it sounds like - a clear coating of paint. Its this stuff that adds the shininess to your paint job and makes it look like a car.

The biggest drawback to spraypainting is the time it takes to get a good job. With atleast one coat of primer, two-three coats of paint, and a layer of clear-coat, the whole process can easily go over a day (you need to give a few hours for the paint to dry in between coats).

I learned about all this from case-modding sites (some people are crazy enough to make their computers look like ferraris :wink: ). If you want more details, go to sites like Virtual-Hideout or Bit-Tech and search their forums for “painting guide”

Don’t know if anyone is still reading this page, but here is my info. As far as I have read, anodizing dosn’t actually require very special equipment, but I have never done this. Anyways, a page which I think has been helpful (once again, I have finals this week and havn’t been able to try it) is this:
http://www.warpig.com/paintball/technical/anodize.shtml
As far as I can tell, the author of this page knows what he is talking about. I have read elsewhere that the process and materials he uses are perfectly fine and can produce some nearly “professional” quality results. I plan on trying this out in about a week, and I will be sure to post the results here.

Happy Engineering,
El Bob

You might want to look at this paint called Duplicolor MetalCast. It is supposed to look like anodizing.

we used that on our robot cart this year and there were a few problems with it:
1.) alot of prep work to follow the directions so it is bad for large objects.
2.) it is very runny and hard to get an even coat.
3.) it comes off way to easy, just a slight rub and it will come right off.

So i would only recomend it for small parts that wouldnt get hit or abused much

and u have a limited amount of colors: red, blue, yellow, green, purple, and a silver primer they have so u can do it on wood

in response to the original question, or for future use,
you can use tail light paint for cars, it lets light through while tinting it a certain color, i beleive some rc car paints work the same way

We had the telescoping arms on our robot anodized blue this year. As for retaining the gloss, it’s not 100% shiny, but it still has some shine to it. Look here and here for a few examples of what it looks like.