Etching then anodizing or vice versa

[Remulos]

I want to anodize some parts of my piece as well as (acid) etching. I'm familiar with both separately but not together and was wondering what experiences people have had with different orders.

In my mind it makes sense to anodize and then acid etch using vinyl to mask the parts I don't want etched but I'm curious about what the effect will be of a shallow etching and a deeply absorbed colour.

I've seen several posts on here where people have etched and then anodized but I'm curious as to how the anodizing process works on an etched surface. i.e. does a blue dye turn the piece blue and dark blue in the etched places or was a mask used to cover the already etched parts? This website says that you should etch first to help remove flaws in the piece but if you're just etching a small pattern then surely this doesn't really apply? http://aluminumsurface.blogspot.co.uk/2009/10/acid-etch-hot-topic.html

Any thoughts, or even better, pictures would be very helpful.

[darth_chasm]

You're referring to two different types of etching for two different purposes. The one in the link is a surface preparation step often used in anodizing as the step right before the anodizing bath. Then there is decorative etching. They are completely separate of each other.

The surface prep etch is often done with lye, nasty stuff, and will create a more matte finish than without.

Below is a piece I first salt water etched with a vinyl mask. Then anodized using sodium bisulfate rather than sulphuric acid. I skipped the prep etch in lye altogether.

http://i12.photobucket.com/albums/a228/mditomo/B77DB3FF-6FAC-495B-A020-DE1AB442691B_zpslnfm8rrh.jpg (http://s12.photobucket.com/user/mditomo/media/B77DB3FF-6FAC-495B-A020-DE1AB442691B_zpslnfm8rrh.jpg.html)

[Remulos]

I know that they're not the same however they both change the structure of the outer layer of the aluminium so I just wanted to check. The reason why I am curious is because I will follow a similar process to you (acid etching for the decals and Sodium Bisulphate anodizing for the colour) but I can see from your picture that the original finish left by the SWE has been changed by the dye whereas I want the original colour.

However I think this has answered my question (even if not the way you thought :D ) so thank you!

The conclusion I have come to is that the anodizing only really effects layers in the ?m scale whereas acid etching goes a lot deeper and therefore should theoretically etch into the un-dyed aluminium beneath.

EDIT: This was supposed to say micrometer scale but it doesn't like the micro character for some reason.

[darth_chasm]

Ah I see. Well you can experiment. Not really sure if the decorative etching process will eat through the anodized layer. Different chemistry and I'm no chemist :)