Sodium Hydroxide (Caustic soda) Alternative

[2scoops]

Hi,

I don't really like using Sodium Hydroxide (caustic soda) to remove the Aluminum Oxide before annodising because, apparently, it attacks alumium as well as the oxide and because one drop in the eye and you're blind. Can anyone reccomend an alternative (and concentration) that I could use.
I have access to a chemistry lab so use fume cupboards and should be able to get hold of any chemicals.

[destroyer125]

I believe nitric acid will do it to.....but Id hate to get that in my eye too

[acidrain]

Most of the chemicals used for anodizing are dangerous, and safety measures should always be used. Stripper is no exception.
As for attacking the aluminum, here is what I do...
Clean the parts first in either lacquer thinner, or strong detergent.
Strip at no more than 70F.
Watch the parts closely, and "help" the stripper by occasionally scrubbing with a toothbrush or other means. It usually take no more than a few minutes to strip a part.
Once the parts are stripped, immediately pull them and rinse. Go straight to the de-smut step.
If you are leaving the parts in for a long time because there are stubborn areas, it's because the parts were not cleaned first (oil, grease, paint, etc. will inhibit the stripper).

[sage]

I've posted this somewhere else so I won't elaborate too much. If you don't like the etch. Try "Spray Nine" made by Knights. Available in Canada at Canadian Tire. Must be in the US somewhere as well. It's a houshold cleaner. I get it in the spray bottle. Spray it on, use a tooth brush to get into the corners and rinse it off with tap water with the tooth brush again, then with DW if you want. Go right to anodize with 6061 or to desmut if you want (I don't). It passes the water break test everytime perfectly. It is slightly caustic but never messes up my ultra polished pieces finish.

Sage

[2scoops]

Originally Posted by acidrain

Once the parts are stripped, immediately pull them and rinse. Go straight to the de-smut step.

How do you de-smut exactly?, are we talking chemically or by toothbrush!.

[-AAPB-Eric]

chemically. if you get the caswell LCD ano kit it comes with it.

[sage]

Right - use the Caswell de-oxidizer and de-smut. They sell it separately. I never used it before but I tried it recently. I didn't notice any difference in my results but I use strictly 6061 and I think the desmut removes surface copper, which I don't think 6061 has much of anyway. I just go right from Spray Nine and rinse really well to the anodizing tank.

Sage

[destroyer125]

6061 still gets a smut, but it is easily whiped away compared to other series of aluminum

[sage]

Maybe you do, but I don't, so I guess there must be something else going on.
I just finished a 11x7x1/2 inch plate of 6061 anodized at 6A/sqft. and the finished product came out of the sealing tank like it was just professionally painted. Nothing else required. No rubbing, polishing or WD40 to cover up the problems. Just a bright shiney black plate.

Sage

[M_D]

Smut is used as a broad term, and there are several different causes for it, as it can happen in several of the steps in the anodizing process. 6061 isn't as bad as some alloys, but stripping or etching it will produce a smut that is easily removed with the de-smut solution.

Smut that is formed in the anodizing tank, dye tank, or sealer tank is different.

When everything is in balance, I too find the parts will look great after sealing with no additional steps.