Aluminum anodizing

[Crow]

So I read up on how to anodize aluminum.  I’d like to anodize a large backpack external frame (because I don’t like my hands turning grey every time I handle it and paint doesn’t work terribly well), but really don’t think taking on something of this size myself is the best idea.  Does anybody know a place (or have the ability themselves) that I could hire to do this job, and how much it might cost?

[DancingBear]

I know there’s a place in Indianapolis that does it, but I haven’t worked with them.  There’s probably some place in any good-sized city that can do it.

I have had to deal with machine shops and metal fabricators before, and my experience has been that you’re best off calling them on the phone and discussing what you want to do with someone there, as opposed to looking at websites or sending an email.  Most shops aren’t really geared toward working with individuals, and their rate sheets reflect running large batches, with prices to match.  But if you talk with someone there (particularly at a smaller company) they may be able to slip your job into a larger run and give you a better deal. A little flexibility about deadlines and possibly color could help a lot.

I think you’re wise to farm this one out.  A backpack frame is a pretty big piece to try to do yourself, particularly for the first attempt.

Good luck!

Walt

[Anonymous]

Is the frame already put together?   If not, you could anodize the individual tubes fairly easily.

[Nick Gatel]

Have it powdered coated. You can even give it a wood look, which would be cool for Justin.

[Crow]

Yeah, the frame is already complete.  Nick, do you have experience with how well powder coating holds up on aluminum?  I have only had steel powder coated but while it’s more durable than paint, I thought anodizing would be better for aluminum as it would be even more durable and also harden the metal…

[Roger Caffin]

You could also consider giving it a thin coating of EPOXY primer. Sticks well.

Cheers

 

[IVO K]

…as it would be even more durable and also harden the metal…

Make sure to not get sucked into what is called “hard anodizing”.

While it would harden the surface of your frame, stresses in the frame during service could result in microcracks in the hardened skin layer, which could then easily propagate throughout the “meat” of the frame, getting it ruptured and broken.

This was observed in the bicycle industry some 2 decades ago, and once the reason for the failures was understood, the practice was rapidly abandoned.

Why do you need a hardened frame? What improved function would it have that is not there in a “non-hardened” frame? Are you sure you really know what are you getting into?

[Crow]

Ahh, good to know, thanks.  I don’t need a hardened frame, just thought it would be a good idea.  I guess not.  Will look into epoxy primer and/or powder coating, then…

[Nick Gatel]

Yeah, the frame is already complete. Nick, do you have experience with how well powder coating holds up on aluminum?

Sort of… on my motorcycle, but the parts don’t get exposed to the abuse that a pack frame does. The aluminum engine had an epoxy clear coat from the factory, and when I rebuilt the engine I had to bead blast it to get it off. The power coating company will be able to tell you how well it will hold up. And of course you could just polish with a 3 step rubbing compound process that will give you a chrome-like shine, which is what I did on most of my aluminum parts on the bike, but it is a long and dirty process.

One word of caution. There are some high temp paints that work well and need to be baked in an oven. I had great luck with that until my wife caught me with motorcycle parts in HER oven. That created a bit of a temporary marital problem and she made me buy an oven for the garage.

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