Solution life

[lightway]

I have been using my anodizing solution for 1 year, are there ways of verifing the quality. Are there symptoms that indicate solution problems such as ;
high voltage requirements at start-up - this condition makes it difficult to observe PAR.

[sswee]

Originally Posted by lightway

I have been using my anodizing solution for 1 year, are there ways of verifing the quality. Are there symptoms that indicate solution problems such as ;
high voltage requirements at start-up - this condition makes it difficult to observe PAR.

Are you talking about the quality of the electrolyte? High voltage requirement is an indicator of high resistance. Does the voltage stay high during the run or drop after start up then go to a normal level? A weak electrolyte would cause high voltage levels all through the run. You said you're observing PAR. The 720 rule will give more consistent results. Are you using a battery charger? It would help evaluate your problems if we knew more detail on your setup and parameters of a problem run. SS

[lightway]

Yes- i wonder about the quality ( contration) of the electolyte....I am using the Caswell 3A digital power supply...voltage climbs within 15 seconds of sart-up.and typically remains there thru the cycle Voltage usually exceeds peak voltage as per 720 rule from the start. . CD - 4.5 Thickness - 0.7
I am confident all my connections are good - (soldered to cathode plates) and clean secure connection at part bus-bar and clamped ( Ti tipped plastic c-clamps) to parts. Parts are cleaned: - acetone - glass beaded - phosproic acid cleaner. Thanks...DH

[sswee]

A PH tester would be the only way that I could think to get an acidic level without a lab test. My electrolyte is barely over a year old and showing no signs of anything wrong.
How high is the voltage going? The 720 rule calculation for peak voltage can't take into account all the variables. Tank temp will vary +-2V. Incorrect SA of a part, size of the lead connected to the part. Has this just started recently with no other changes having been made. Please share whatever you find with us for the next guy. SS

[lightway]

ph testers @ this extreme acidicity level ( pH 1) are expensive, the digitial "hydrophonic" products range out at pH4.
Voltage climbs to 12-14 V, verified voltage accuracy of supply power with meter.
I use CAD program "Solidworks" to calculate SA , with adders for wire (Ti),
I have experienced this problem from first attempt.
I have removed and cleaned cathodes, using 5 gal pails so anode to cathode distance is usually 3".
I don't use a tank heater, (ambient 60-75).
I'm considering a re-mix of the solution, just to start fresh again.
I'll do a time vs voltage graph on a sample panel.
Thanks again.

[sswee]

This is the one I'm looking to get shortly.
http://www.caswellplating.com/kits/ph_tester.html

Sounds like your going above and beyond on everything. From what you've covered, I can see where you might be looking at the solution. I'm still surprised if the electrolyte is causing problems this soon.

With aeration, my voltage initial fast ramp took 10 to 20 minutes to get within approx. 4V of the peak and start a slow climb to the peak. Since changing to a pump for agitation, the initial fast ramp occurrs in the first 5 minutes then starts the slow climb. I prefer low to mid 60's for my runs. The only time I heat is when it gets below 60.
SS

[neilfj]

We (Paul & I) actually figured this out mathmatically. Acid life is directly related to the total amount of anodizing performed and the thickness of the anodizing, as it is based on the total amount of dissolved aluminum present in the electrolyte. According to Light Metals Finishing Process Manual by David Montgomery, aluminum dissolves at a rate of 1 gram per sq ft of aluminum per 0.8 mil of anodizing produced. He also states that the total concentration should not exceed 12grams/liter of electrolyte.

For larger anodizers using higher concentrations of electrolyte, they decant, titrate and add acid as required, to rejuvenate their electrolyte. This isn't cost effective for small anodizers, so we determined that at LCD acid concentration of approx. 5%, and using the 5gal buckets supplied by Caswell, replacement of the electrolyte would not be required until a total of 136sq ft of aluminum was anodized to a thickness of 0.8 mil (20 microns). The thinner the anodizing produced, the longer the acid lasts and vice-versa for thicker coatings. We added quite a bit of 'slop' to this number, so its not like you will begin having problems once you cross the 136sq ft total. We figured it was a good 'rough' quess for the small anodizer.

[cameraman]

When I'm anodizing, my nose picks up the smell that it identifies as "battery acid". Is that really just hydrogen or is the acid slowly leaving the solution? In other words, will the acid stay there for the whole 136 square ft? I keep a log of all my anodizing runs, including the surface area. I'll know definitively when I approach the 136, but will there be any other indications when the solution is nearing the end of its life, for example, more problems with dissolution or decreasing dye depths due to decreasing anodization layer thicknesses?