etch....??

[Sid03]

I just remembered a question that I have been wondering for some time. What is "etch"? Ive seen it mentioned in caswells ano guide, but I dont think it actually says what it is or what it does. Ive seen it mentioned in other ano literature.....but still not mentioning the purpose, the chemical used, or anything. They all just say to "etch" the part. I give up, could somebody be kind enough to explain? Thanks

[M_D]

]Etching essentially is when a solution is eating away the outer layer of aluminum. It will leave a flat appearance; so on a part that was shiny to start the part will become dull. On parts that have a real rough texture, it may actually smooth it some.

Sometimes various acids are used, but usually it is an alkaline-based solution (sodium hydroxide, aka lye). The etch does help to further clean the parts, and also is done to even or improve the surface finish, so it can be thought of as a chemical tumbling.

Some parts that have a heavy oxide layer can really benefit from the additional cleaning. Other parts that are already clean may not show much if any improvement. If you are working with polished or smooth machined parts, and don’t want to dull them, then you would want to skip this step or keep the treatment time short. Also, as the solution is heated it becomes more aggressive.

The SP cleaner Caswell’s sell will etch parts if heated, heating it to 200 or up to boiling makes it very aggressive compared to 120-150º, and will really clean plus etch at that temperature. Often parts need to be de-smutted if they etched, because a layer of smut forms.

There are more ways to skin a cat than just one, and the same goes for anodizing. Much of the technique depends on what you want. There are two main things in part prep for achieving a good consistent anodize layer, and that is the parts need to be squeaky clean and as free of oxide as possible. How you accomplish that doesn’t seem to be important, but various methods may alter the appearance and final look.

[Zouky]

as i understand, microetching will remove some oxide layers and therefore oxide layers will be removed if there is any.

if you say that we need to make sure there is no oxide on the parts, does it also mean we need the etching step?

thanks

Andy