Anodizing

john bunsenburner · Mon Jul 06, 2009 11:01 am

Would anodizing increase the pressure rating?

twizi · Mon Jul 06, 2009 11:56 am

i would think it would weakin it

spudtyrrant · Mon Jul 06, 2009 11:56 am

john bunsenburner wrote:Would anodizing increase the pressure rating?

no it should actually very slightly decrease it because the acid eats away at the surface before the color bonds to the aluminum

twizi · Mon Jul 06, 2009 11:57 am

ha beat

ya we must have pressed enter at the same time

john bunsenburner · Mon Jul 06, 2009 12:05 pm

Well the layer that builds up makes the metal stronger, but I am not sure if it is stronger overall or just more scratch resistant.

twizi · Mon Jul 06, 2009 12:12 pm

it more scratch resistant i think

theBOOM · Mon Jul 06, 2009 3:39 pm

actually its creates a protective layer over the aluminum but im sure it wouldnt increase the pressure rating drastically..

inonickname · Mon Jul 06, 2009 11:55 pm

God. It forms aluminum hydrate which is much stronger and better wearing than aluminum. So yes, it makes it stronger.

Moonbogg · Tue Jul 07, 2009 12:07 am

Anodized aluminum is also not electrically conductive

john bunsenburner · Tue Jul 07, 2009 3:25 am

Well moonbogg that is only partly true. The hydrate layer is not, if you hook up an electric supply it won't conduct. However, the aluminium below is still conductive, you can't put a pieze igniter with a bare wire through a hole on an anodized chamber and expect it to be insulated by the alli. However you can drill the hole and then anodize, this giving you a electrically not conductive hole for your piezo. The hole's size would reduce during the anodizing, so you have to drill it slightly over sized.

inonickname · Tue Jul 07, 2009 4:00 am

I believe the layer is extremely porous, and anyway the voltage from a piezo would easily get past any insulation the very thin layer provides

jimmy101 · Tue Jul 07, 2009 12:39 pm

inonickname wrote:God. It forms aluminum hydrate which is much stronger and better wearing than aluminum. So yes, it makes it stronger.

I kind of doubt that. Aluminum hydrate may be harder but it is also probably much more brittle than is Al metal. The hydrate also decomposes at high temperatures (>200C) and is often used as a flame retardent.

But isn't anodized Al coated with Al2O3 and not the "hydrate" (Al(OH)3), which should be called aluminum hydroxide). The hydroxide isn't going to exist for very long in the typical acidic anodization bath.

Al will self passivate in air very quickly. The problem is the coating isn't very sturdy and can be rubed off easily. The point of anodization is to form a more robust coating and to provide a suitable surface for dying and/or painting the metal.

The anodized layer is typically less (often much less) than 1/1000th of an inch thick so the affect on the strength of the part is insignificant and probably unmeasurable.

Davidvaini · Tue Jul 07, 2009 2:39 pm

inonickname wrote:
mark.f wrote:Why not just paint it?
Paint looks rubbish, scratches and is not even unless it is airbrushed. If I were to paint it I'd coat it with epoxy and a colored powder. This one will just be polished and varnished.

Yes I agree with this, unless you are an experienced spray painter.

(Plain old Red coat of Rustoleum spray paint. No buffing, polishing or anything afterwards.)

But I agree that spray paint is more suceptiable to scratching especially when not properly applied.

(and yes I do computer case modding.)

THUNDERLORD · Tue Jul 07, 2009 5:37 pm

...The anodized layer is typically less (often much less) than 1/1000th of an inch thick so the affect on the strength of the part is insignificant and probably unmeasurable...

Well said.
Even with chrome,nickel or silver plating, Etc., same thing.
No need to re-size anything including the barrel bore.
Also the reason it's most important to polish the bare metal first.
(For a good finish) 8)