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Acid etching before anodizing
August 12, 2009
Our company is one of the leaders in manufacturing of anodizing aluminum extruded profiles in the Russian market.
Anodizing technology, as we know, implies a pre-etching of aluminum in alkaline solution of caustic soda
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. When we were visiting the trade show in USA we have seen the presentation and heard the report about the acid etching of aluminum as an alternative to alkaline.
As we understood acid etching creates a matte surface with a minimum etching deep into metal, but also removes the metal defects such as scratches, bully, etc. The products for acid etching made on the basis of fluoride (i.e., we do not know), has a pH = 4.5-5.5.
The temperature of the acid etching of 105-1150F, the recommended time of etching-1-3min.
Chemical reactions that are in the process of acid etching of the following:
NH4HF2 ------> NH4 + HF
2 Al +6 HF -----> 2 ALF3 + 3 H2
We would like to know whether you are familiar with this technology and what is your opinion about it's perspectives. Your opinion is very important for us because nobody in Russia works with this technology and European specialists haven't shared vision for it.
Thank you in advance.
Natalie
anodizer - Moscow, Russia
Hi, Natalie. Acid etching has been around for a while to varying degrees. What you saw at the exhibition and heard about in the conference was doubtless a proprietary product rather than a generic concept. But if anyone has operating experience with acid etching, they will hopefully provide you their feedback.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 12, 2009
Check out some old patents that have expired. Non etch acid cleaners and light etch acid etching solutions have been around for over 40 years. The one that I used was a proprietary that was mainly phosphoric acid and surfactents.
Fluorides tend to be in the desmut step. Check out some literature on tri acid etch/desmut. A mix of nitric, sulfuric, fluorides and water.
- Navarre, Florida
August 13, 2009
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