anodizing II

[Ant]

I chanced upon the anodizing thread- actually, the un-anodizing thread with a link to anodizing
instructions. this sounds pretty tempting, and as i will be making the odd aluminum part this
spring, i thought i might give it a try. time permitting.

does anyone know if anodizing changes the surface material? as in- if i machine a 27.2 mm seatpost,
and anodize it, will it end up being
27.1 mm? or 27.4? i am unfamiliar with the chemical/physical basis for the process, and would rather
know before hand so i can compensate when i am making parts.

or perhaps it changes nothing.

thanks,

anthony

 

[Paul Wakerley]

Anodising is the controlled formation of aluminium oxide at the surface of items made from aluminium
and its alloys. When the coating is formed, it grows the surface by approximately 50% of the
coatings thickness. Remember that this is per face, so component size growth will be X2 film
thickness for a diameter.

If the coatings are thin (i.e. less than 10 microns) or the application is not dimensionally
critical, then this effect can be ignored.

Check out http://www.acornhardas.co.uk/datasheets.htm this is a company I used to work for, who
pretty much invented hard anodising back in something like 1920.

Paul

"ant" <[email protected]> wrote in message
news:[email protected]...
> I chanced upon the anodizing thread- actually, the un-anodizing thread with a link to anodizing
> instructions. this sounds pretty tempting, and as i will be making the odd aluminum part this
> spring, i thought i might give it a try. time permitting.
>
> does anyone know if anodizing changes the surface material? as in- if i machine a 27.2 mm
> seatpost, and anodize it, will it end up being
> 27.1 mm? or 27.4? i am unfamiliar with the chemical/physical basis for the process, and would
> rather know before hand so i can compensate when i am making parts.
>
> or perhaps it changes nothing.
>
> thanks,
>
> anthony