Surface roughness after hard anodizing
 

Thanks in advance... I am an avid reader of this newsgroup (and
occasional contributor), and know how much knowledge exists in this
group.

I have some parts that are being extruded and will be hardcoat
anodized. They are posts that attach to an aluminum base to batch parts
in between processes... a robot will load/unload them from this pallet.
The surface finish on the posts should be smooth so as not to scratch
the parts if they graze them going in/out of the pallet. I am making
100 of these pallets, which works out to 3000 of these posts...

I am worried about surface roughness... I have seen some parts after
anodizing that are pretty smooth and some that were somewhat rough. Is
there any special preparation to ensure an Ra 32-40 microinch (give or
take) finish?

It seems that the anodizing process would inherently produce a somewhat
rougher finish than the bare metal as it creates a layer of oxide... is
there any suggstions for what finish I should spec on the bare
extrusion?

Any other suggestions along these lines... I am new to the extrusion
game. Any other coating suggestions? I need something that is hard,
durable and rather inexpensive. I have looked into Nyflor, a
Teflon-impregnated coating that is laid down after nickel, but the cost
of the coating was 5x more expensive than the total part cost w/
hard-anodize!

Thanks a million...

Adam S

Surface roughness after hard anodizing
 

Adam,
The rule is that you get exactly what you give. In other words, every mark
shows up after being hard anodized. Every scratch which you cannot feel
before will be felt after. Even the best tool finish will look terrible
after. My experience is that every piece should be tumbled and then buffed
first.
Steve

"Adam" wrote in message
oups.com...
Thanks in advance... I am an avid reader of this newsgroup (and
occasional contributor), and know how much knowledge exists in this
group.

I have some parts that are being extruded and will be hardcoat
anodized. They are posts that attach to an aluminum base to batch parts
in between processes... a robot will load/unload them from this pallet.
The surface finish on the posts should be smooth so as not to scratch
the parts if they graze them going in/out of the pallet. I am making
100 of these pallets, which works out to 3000 of these posts...

I am worried about surface roughness... I have seen some parts after
anodizing that are pretty smooth and some that were somewhat rough. Is
there any special preparation to ensure an Ra 32-40 microinch (give or
take) finish?

It seems that the anodizing process would inherently produce a somewhat
rougher finish than the bare metal as it creates a layer of oxide... is
there any suggstions for what finish I should spec on the bare
extrusion?

Any other suggestions along these lines... I am new to the extrusion
game. Any other coating suggestions? I need something that is hard,
durable and rather inexpensive. I have looked into Nyflor, a
Teflon-impregnated coating that is laid down after nickel, but the cost
of the coating was 5x more expensive than the total part cost w/
hard-anodize!

Thanks a million...

Adam S

Surface roughness after hard anodizing
 

I worked in a decorative anodizing plant, the other half of the plant
did the extrusions. Part of the start of the process was removing the
oxide film in a very aggressive hot alkaline bath. Any polish the
parts had was gone at that point. Anodizing produces a somewhat
brittle surface, any impact will crack the coating. Wouldn't be my
choice if I wanted a really smooth surface to avoid damaging parts
rubbing on it. From the process books, hard anodizing looks like it
gives a pretty rough finish, one process called for sandblasting the
parts prior to cleaning, etching and anodizing. And it's only
relatively hard, the oxide surface will be hard, the surface under it
will be as soft as the original aluminum. If it's not a heat-treated
alloy, that can be pretty soft.

We also did powder coating, which would be my finish of choice. These
days, you've got your choice of epoxy, polyester or urethane, we never
had urethane. Epoxy was the most durable of the finishes we did. Any
of them, properly done, will adhere to the surface even when the part
is bent double, with no cracking or peeling. If you've got mounting
holes in the parts where the hangers could go, it'd be fairly cheap to
do on a production basis. Certainly should be cheaper than anodizing.
Some experimentaiton would be needed to find out whether epoxy or
urethane would stand up better to your proposed use. Properly cured,
you can take steel wool to either polyester or epoxy powder coats and
only dull the finish, they're pretty abrasion resistant.

How much load are we talking about here? 1 oz. parts or 1000 lb.
parts? Might be neither process would be suited to your needs.

Stan

Surface roughness after hard anodizing
 

Thanks for the replies so far. I think I may look into the
cost/feasibilty of powdercoating... at least have another alternative
to show the powers-that-be...

The parts are only ~.6 ounces, optical-grade acrylic. They are
disc-like parts that will be stacked and held captive by these posts.

Anyone ever hear of post-processing hard anod... polishing the softer
outside layer down to the harder inner core of the coating? I found a
little bit about this online, but it was pretty vague.

Surface roughness after hard anodizing
 

"Adam" wrote in message
oups.com...
Thanks for the replies so far. I think I may look into the
cost/feasibilty of powdercoating... at least have another alternative
to show the powers-that-be...

The parts are only ~.6 ounces, optical-grade acrylic. They are
disc-like parts that will be stacked and held captive by these posts.

Anyone ever hear of post-processing hard anod... polishing the softer
outside layer down to the harder inner core of the coating? I found a
little bit about this online, but it was pretty vague.

You can make a very durable and hard finish on aluminum. My Porsche has
aluminum cylinders (the entire block and head) no sleeves. They do it with
a special honing compound Nickasil IIRC. It makes a Nickle Silicone glaze
on the aluminum and works quite well for cilinders. I have no clue as to
the feasability of putting it on Aluminum Extrusions.

Glenn

Surface roughness after hard anodizing
 

"Glenn" wrote in :

ittle bit about this online, but it was pretty vague.

You can make a very durable and hard finish on aluminum. My Porsche
has aluminum cylinders (the entire block and head) no sleeves. They
do it with a special honing compound Nickasil IIRC. It makes a Nickle
Silicone glaze on the aluminum and works quite well for cilinders. I
have no clue as to the feasability of putting it on Aluminum
Extrusions.

Glenn,
Nikasil®™ is a chemically bonded and etched coating similar to hard
anodizing. It must be 'worked' after coating, as the surface is rather
rough, very similar to a hard anodized surface.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

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