Proper prepping of aluminum for anodizing

[Coelacanth]

Is aluminum polished to a high sheen suitable for anodizing? With painting, you want something like a 400-grit surface for the paint to adhere well, but I'm not sure what's best for the anodizing process.

I got good results with the parts I had anodized for CYANide by sanding up to 800-grit, but I'd think going all the way to 1500+ and then polishing with rubbing compound to a high sheen would look fantastic when anodized...I just don't know if the ano needs a rougher surface to stick well and be durable.

I have a somewhat related question. I have an Integy blue alloy servo horn that has a fugly "25" stamped on it (Futaba # of teeth) in white paint. I can't seem to remove it, neither acetone or Castrol Super Clean did a thing to remove it. I didn't want to use Easy-Off oven cleaner because that'd remove the anodizing. Ideas?

[Charlie don't surf]

Careful with super clean, it will pull the anno of too-

A high polish is not a good surface for anno, but they usually prep with a quick caustic soda and neutralizer as I understand- the small unevenness creates a good surface for the crystals to adhere-

[Coelacanth]

Careful with super clean, it will pull the anno of too-

A high polish is not a good surface for anno, but they usually prep with a quick caustic soda and neutralizer as I understand- the small unevenness creates a good surface for the crystals to adhere-

So, if I go up to 1000-grit and rubbing compound, the chemical prep will do what it needs to do for the ano to stick? Or just leave it at 800-grit & no rubbing compound?

[Charlie don't surf]

I think in general, the more "textured" the surface, the better- and remember, you can send it mirror polish, but once it is in the etch tank, it will not be a mirror anymore-

[murphy3428]

Sanding really does't have anything to do with proper adhesian for anodizing its the etching process the only reason for sanding or polishing is for personal preference and of coarse labor costs if your a business. As for aluminum and paint before powder coating was around my fathers shop use to have to send out all the aluminum parts to the platers for zink plating inorder for the paint to adhear to the aluminum.

[jwscab]

anodizing is a chemical process to oxidize the aluminum at a controlled rate and uniformity. the texture of the part being anodized is strictly a function of the desired finish.

parts that are machined and directly anodized, will show up as a shinier, almost glossy finish, much like the typical blue associated shocks. because the process is controlled for something like that, they can go right from a machining process to a light wash/rinse directly to anodizing.

aftermarket anodizing companies will almost always use a caustic wash prior to anodizing in order to make sure the customers parts are well anodized, as any surface contaminants will cause a blotchy finish, the caustic bath will also ensure a uniform surface finish due to etching the surface and removing any existing oxidation.

if you don't have any specific finish requirements, most places will do a caustic bath to remove any prior finishes, and will look pretty much like what is already there. if you want to polish or get a brushed finish, you can always do the prep work yourself, and they might only have to do a very light cleanup.

it's best to talk to the anodizer to discuss what you want.

what's interesting, is hard anodizing. hard anodizing is basically the same as regular anodizing, but done with a very cold acid bath, at much higher currents, to give a much denser oxidation layer.

[Charlie don't surf]

anodizing is a chemical process to oxidize the aluminum at a controlled rate and uniformity. the texture of the part being anodized is strictly a function of the desired finish.

parts that are machined and directly anodized, will show up as a shinier, almost glossy finish, much like the typical blue associated shocks. because the process is controlled for something like that, they can go right from a machining process to a light wash/rinse directly to anodizing.

aftermarket anodizing companies will almost always use a caustic wash prior to anodizing in order to make sure the customers parts are well anodized, as any surface contaminants will cause a blotchy finish, the caustic bath will also ensure a uniform surface finish due to etching the surface and removing any existing oxidation.

if you don't have any specific finish requirements, most places will do a caustic bath to remove any prior finishes, and will look pretty much like what is already there. if you want to polish or get a brushed finish, you can always do the prep work yourself, and they might only have to do a very light cleanup.

it's best to talk to the anodizer to discuss what you want.

what's interesting, is hard anodizing. hard anodizing is basically the same as regular anodizing, but done with a very cold acid bath, at much higher currents, to give a much denser oxidation layer.

So they must have a different cooling process for the bath? I have seen a few chassis get H/A and one worlds chassis burned through the milled section- I have an idea of the correct temps and voltage for the standard process- what are the H/A voltage and temps for curiousoity?

[murphy3428]

anodizing is a chemical process to oxidize the aluminum at a controlled rate and uniformity. the texture of the part being anodized is strictly a function of the desired finish.

parts that are machined and directly anodized, will show up as a shinier, almost glossy finish, much like the typical blue associated shocks. because the process is controlled for something like that, they can go right from a machining process to a light wash/rinse directly to anodizing.

aftermarket anodizing companies will almost always use a caustic wash prior to anodizing in order to make sure the customers parts are well anodized, as any surface contaminants will cause a blotchy finish, the caustic bath will also ensure a uniform surface finish due to etching the surface and removing any existing oxidation.

if you don't have any specific finish requirements, most places will do a caustic bath to remove any prior finishes, and will look pretty much like what is already there. if you want to polish or get a brushed finish, you can always do the prep work yourself, and they might only have to do a very light cleanup.

it's best to talk to the anodizer to discuss what you want.

what's interesting, is hard anodizing. hard anodizing is basically the same as regular anodizing, but done with a very cold acid bath, at much higher currents, to give a much denser oxidation layer.

So they must have a different cooling process for the bath? I have seen a few chassis get H/A and one worlds chassis burned through the milled section- I have an idea of the correct temps and voltage for the standard process- what are the H/A voltage and temps for curiousoity?

The chassis that burned may have come incontact with the tank during the plating process

[Charlie don't surf]

This chassis burned in the milled recesses of the tub, but I just heard about it- and seeing the temps and voltages that standard anno uses, the increased voltage and lower temp ( to decrease resistance? ) also makes sense-

Really cool info!

[Coelacanth]

Thanks for sharing that good info, guys. I guess I'll just prep as I did before and not bother wasting time polishing to a high lustre, as it's just gonna get an acid bath anyway.

[jwscab]

I couldn't really tell you what the voltages/currents are, but I do know that the intensity is such that they need some impressive cooling tanks to keep from overheating the parts and cooking them, as it sounds like with the milled chassis. I wanna say its something like double the nominal standard anodizing volts/area.

Coelacanth, I'd talk with the anodizing place, they might be able to just do a quick wash and not put a heavy etch on the pieces.

[Coelacanth]

A heavy etch would be more durable, I assume?

[jwscab]

no, the heavy etch is just to remove impurities. so if you have a nice clean piece, and it's nice and shiny, they might not have to use a heavy caustic solution, it will be pretty clean already so the finish won't change much. again, just talk with the anodizer for recommendations.

in order to get a more durable anodizing, you go with hard anodizing. it's a deeper oxidation layer and therefore tougher. problem is, you only get a few colors because the oxidation turns dark.

oh, and I stated earlier it's volts/area, it's really amps/volume, and for hard anodizing, the acid baths are run near 0C.