Professional Anodizing - How to?

[tiroth]

I'm going to send out some aluminum plate to be professionally anodized, and I was hoping others who have done this could tell me what kind of surface prep is needed before anodizing. I'd like to end up with a uniform matte finish.

I've already sanded down to a smooth, bright finish on some of my work, but other panels are raw and have reasonably deep scratches. How much work will those need?

I spoke with a gentleman at a shop here who seemed to think that simply doing a longer acid wash (2 minutes instead of 30 seconds) might be sufficient. He had a low opinion of bead blasting that I know is shared by some people here.

Also, are there alloys that won't work well? I use a lot of surplus and have 6061, 7075, and 2024 pieces. Uniformity of finish from alloy to alloy isn't important to me.

Thanks for any answers...I'd certainly like to get the finish right the first time around. Any other tips on how to get good results from professional shops are also appreciated, likely by the shop as well as myself.

[Peter Daniel]

Whatever your panels look before anodizing, they will show same imperfections after the process.

So it's up to you how you want the surface to be finished: either brushing, buffing, sand blasting etching or whatever else.

If you have surplus material, some of it may show surface corrosion (and although it may not visible at the moment, it will show after anodizing).

Sometimes anodizing house can do surface finishing as well, ask them what's the best.

[tiroth]

They were recommending an extra-long bath. Do you buy this as a solution? I would have thought sanding or brushing would be needed.

I think of there being two main steps when I finish Al...the first gets the scratches out and surface uniform, then second gets a nice even shine. In my experience it takes a lot longer to do step two...if you are anodizing, how pretty does it need to look before going in?

Thanks Peter!

[Peter Daniel]

As I said, it has to look as pretty as possible, as anodizing won't hide anythig. In case your "shine" is a bit uneven it will make it more unifirm, but any small scratches/marks will be still there.

When I bruch the panels myself (100/120 grid belts) I try to make even lines and clean everything with Varsol. After that it may still appear that the lines are not that smooth as I might want them, and this is where I use the next step, which is brushing it on Scotch Brite pads (the purple color). This pretty much makes it final finish. If I make it too long on Scotch Brite pads, the surface becomes matte in some areas and this is no good.

Whatever limited experience I have with that, I would imagine that if you try shortcut proper finishing by extending acid wash, they might be able to get rid of the scratches, but in a same way your panel might shrink in size and loose some fine detail (corners and sharp edges). If this is not a concern, then maybe an acid wash is one step solution, but I don't know.

[Bricolo]

So, peter,

the aluminium has to be "clean" and without scratches before anodizing it?
I was wondering it I could anodize my "raw" aluminium gainclone chassis

[Peter Daniel]

It doesn't have to be clean and free of scratches if this is the look you are after anodizing

I'm not really that much concerned with cleaning as they do it anyway before further processing.

[tiroth]

Thanks for the info Peter. Sorry if part of my question was redundant, I think I misread your response initially. Looks like more time on the belt sander for me.

[Magura]

Glass ball blasting is a good solution to make a surface finish that hides as much as possible. It becomes matte and smooth, without destroying the sharp edges (if done right that is).

Magura

[Bricolo]

Originally posted by Magura
Glass ball blasting is a good solution to make a surface finish that hides as much as possible. It becomes matte and smooth, without destroying the sharp edges (if done right that is).

Magura

does it give a smooth finish, or do you see the balls inpacts?

[Magura]

it gives a very smooth finish.....actually its a shortcut to mirror finish


Magura