The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Construction Anodizing Tank - Materials? Agitation?

2004

Q. I have a few questions regarding type II anodizing equipment. I have been getting mixed results and before I commit myself to one thing, I would appreciate some advise. Thank you in advance to all who participate.

I'll start by providing everyone with some background information in regards to my situation. I am quite new to the world of anodizing, its chemistry, its process and its fundamentals. I will assure you all, however, that I have been doing a great deal of research into the field and have successfully produced consistent parts on a hobby scale in my garage (and yes Ted, environmental issues are certainly a concern of mine). Currently I am looking for a reasonably priced printing of "The Surface Treatment and Finishing of Aluminum and Its Alloys" which I am sure will put to rest many of my questions and concerns. In the meantime, I turn to you people.

I intend on fabricating my own processing tanks. Now before some of you jump on the wagon, I should mention I have a fair bit of experience fabricating such things. I do have a few concerns when it comes to the materials utilized in their construction. I have been told by a few people that polypropylene should be utilized throughout the entire line in regards to tank construction. This is not something I disagree with, however, not being particularly educated on the characteristics of polypropylene, I fear that the sealing process (operated around the 200 F mark) will place the polypropylene under immense stress and possibly failure. Am I wrong with my assumption? Should 316 stainless steel be used to construct this high temperature tank?

In short, what I am asking is this. If you people were going to purchase new processing tanks, what would each of the following tank be constructed of :

1 - Pre-treatment
2 - Etching
3 - Bright Dip
4 - Desmut / Deox
5 - Anodizing
6 - Coloring
7 - Sealing (nickel acetate)

With tank construction out of the way, I now have concerns about each tank's method of agitation. I feel that circulation of fluid is the most efficient means of agitation but as I mentioned before, I am quite new to this. Mechanical and air agitation are certainly options. My concern with air agitation is its potential to "chill" a bath in which I am heating and with regards to mechanical agitation, as I said this is a lab scale line of very limited size (3'length x 1' width x 1.5' depth). I fear that mechanical agitation may consume too much of the tank space. To make a long question short, if you people were going to set up a brand new type II anodizing line, which method of agitation would you utilize for each of the tank listed above?

I thank you all for your help here. These are questions that I have been struggling with for weeks now. My gut instinct tells me to use polypropylene for all of the tanks with exception to the sealing bath, where I should use 316 stainless steel. Help? Thanks!

Daniel DeGueldre
anodizing shop entrepreneur - Ste. Anne, Manitoba, Canada

---

---

First of two simultaneous responses -- 2004

Q. I thank you for your advice Mr. Mooney. You have set me at ease a great deal. It is always nice to hear that your gut feelings are, at least, not incorrect. I of course wasn't thinking clearly when I included the bright dipping tank into the polypropylene category. It was in a sense, a brain fart at best. Thank you for clearing that up. Is my face red yet?

Secondly, I am somewhat familiar with the nastiness of the bright dip bath. I had mixed a small batch (2 gallons) a few months ago and did some experimenting with it. Indeed, as you have warned me here (and as I was warned at the time) it is certainly not something to be taken lightly. Air purification and a fume scrubber is at the very least essential. Not a fun cocktail for even the most professional of users I would assume. None-the-less, I still intend on furthering my experiments with it.

This brings another question to mind, a question I will ask in a new post but will propose it here first. Does anyone have any details on how a fume scrubber works. As you may have guessed it, Mr. Joe-Handy over here intends on building his own. Any information is greatly appreciated. Thanks all!

Daniel DeGueldre
anodizing shop entrepreneur - Ste. Anne, Manitoba, Canada

---

---

---

Q. Which grade of SS should be preferred for construction of tanks to be used for hot alkali etching or neutralisation with nitric acid during anodizing process?

Rajabhau Kalbandhe
- Nagpur, Maharashtra, India
September 14, 2012