Aluminum etch additives?

A. You might be just as well off buying a pre-mixed caustic etch. That's what I use. Liquid based, it has all the agents pre-mixed into the make-up. Takes the guesswork out of the whole situation really. There are tons of suppliers of these types of products, listing them would be somewhat pointless as anyone that deals with anodizing and anodizing chemical additives will have access to such a product.

A. Hello fellow anodizer! just browsing and saw this. We use an additive called ax-1888 from Houghton chemical. It is a good chelator; it keeps the solids in suspension therefore gets drug out into the rinse tanks. We have no-dump etch tanks. The aluminum stays between 140 g/l to 160 g/l. I will say that it gives the material a matte finish, not shiny. If that's a problem there are other additives. Well I've probably gabbed enough. It's just a thought.

A. I was looking for information about sodium gluconate in solutions of sodium aluminate. I have found something that may helps you: I think you should add 1% to 5% of gluconate to your bath. I found that in Vulcan Chemicals-Technical and environmental services: "Caustic Etching of Aluminum"

A. My friend I am also involved in the anodizing process. You can use 10 grams/liter of Sodium gluconate.

A. Hi Paul. Yes, it's possible to use a single tank both as a soak clean and an etch, and some small labs certainly do so. But it's not good practice for a production shop to combine the two processes because it opens the door for unintended consequences -- as soon as you have a cleaning problem, you'll find yourself over-etching, which means you'll have to over de-smut; plus you may have more carry over of oils this way; finally, you'll probably be dumping more than you should because the tank will fill with both soils & aluminum, and you'll have to dump as soon as either becomes a problem.

As for proprietaries vs. home brew, I think you should try to find out from experience how much the proprietary really costs you in practice vs. how much you really spend in practice if you try to do without. You might find that the additives prolong the solution life more than you anticipated, such that a pound to pound comparison isn't really useful.

You obviously know more about your business than I do, so this is just repeating an aphorism, not me presuming to "lecture" anyone ... but there is a saying in the industry: If you can't afford the cost of the customary chemistry, you might be doing the wrong work for the wrong customer at the wrong price :-)

Luck and Regards,

A. How's the etching results? Basically etching is generally dependent on caustic concentration and aluminum content and temperature of bath. I have also faced same problem many times but the results were same though the colour of bath changed. If etching is okay don't worry about the colour.

Regards

A. Your etch bath had been out of control:)

Firstly, you should analyse the bath. caustic soda [affil links] had fallen down in the bath as aluminium hydroxide. This situation is not sustainable for production. Also you should check bath's bottom for any precipitate. If you realize any precipitate you should [transfer] etching bath to another available bath for cleaning the bottom of bath. If you don't realize any (or acceptable) precipitate, than you should increase caustic soda [affil links] to 85-95 gr/lt (if you find result 50 gr/lt). You should catch a balance between caustic soda and dissolved aluminium. Also temperature should be 60-70 °C. during production. Balance of bath will improve day by day, but you should focus on these parameters during every day.
Good luck,

? Hi Manauwar,

Please explain your situation, so that we can have an idea what you are trying to do. Are you wanting to etch as a preparation for anodizing, or are you looking at getting a dull, matte finish?

A. Hi Manauwar. You haven't introduced yourself yet, so we don't know what you know and what you don't know ... but people usually buy these kinds of process solutions rather than trying to mix them from commodity chemicals. Wernick, Pinner & Sheasby.
has a 13-page chapter on the subject. As explained there, caustic soda [affil links] at 4 to 10%, and operated at 40-90 °C can be used, with or without a wetting agent.

They go on to say that dealing with the widely varying dissolved aluminum content is a significant problem which can be addressed with bleed & feed, precipitation with alkali metal silicates, use of an etch recovery system, or (perhaps preferably) by chelation of the aluminum with sodium gluconate. Etches can also be accelerated with nitrites or nitrates. The same book also lists the effects of 47 other different additives on the etching process while claiming that there is no cohesive theory about the subject, just empirical results.

Probert's "Aluminum How-To" offers a more condensed and "problem solving" approach to the subject, and includes some practical hints about formulation like using about 4 oz./gal of chelater, but doesn't actually offer an exact mix. I think I'd urge you to buy a proprietary etching process unless there is a compelling reason not to. Good luck.

Regards,

A. Hello again Manauwar. If it's not a matter of formulation, you may be etching too long, or too hot ... or perhaps an acid etch would be better for your needs.

Apologies, but I have the feeling that English might not be your first language, and you might ask an interpreter to help. Because you've posted on this site many times, and each time you do I refer you to our page: "Why won't they answer me?!", and ask you to please post full details of your situation. You never do, you never acknowledge our answers, you never reply with requested data, you just move on and post another abstract sentence fragment as your next question, so I don't know if you've received any help or we're just wasting each other's time :-)

Regards,