Quick question on "old" ano method......

[Fibergeek]

You find that its not hard to set the angle of the holes so that the jets of electrolyte don't break the surface. I'm recirculating 5 gallons at 420 GPH that's 7 GPM, it takes 43 seconds to cycle all of my electrolyte. The surface looks dead calm, but 1 inch below and to the bottom its really moving. I have no bubbles sticking to the work or the cathode ever.

I have many anodization curves for 1100, 2024, 6061, and 7075, at ASFs from LCD through 21 ASF. I'm not at liberty to share them until early July.

I'll cheat a little and just verbally describe a few.

These were 90 minute anodizations to grow "Type II 1/2" coatings up to 3 mils. thick, not what you would want.

18 ASF, 70.4 deg. F. 1:1 electrolyte, very accurately instrumented.

2024 started (+3 minutes) at 1.22 Ohms/sq,ft., and gently sloped downward to 1.05 Ohms/ sq.ft. at +90 minutes. The final coating thickness was 17um (0.7 mils) there were signs of dissolution (chalky residue) but dyeing was fine.

Contrast this to 6061; same ASF, temp., time, and electrolyte:

This rose rapidly to 1.10 Ohms/sq.ft. at +5 min. they continued to rise at a slower rate to 1.62 Ohms/sq.ft at +90 min. The thickness was 70um (2.75 mils.) no dissolution signs, dyeing also excellent.

I didn't provide voltages as these would be meaningless since the size of your work is so different than mine. You can calculate what the voltages would be for a given surface area.

PAR was not evident, I have found out with a lot of testing that it only works with weak electrolyte, and is most visible at LCD ASF ranges, it will not be visible at all with racking.

[sage]

Can some one please translate the 1:3 or 10% or grams per litre acid measurements to something I can easily measure like specific gravity. I have used my acid bath for quite some time and I know I've lost a lot of water through evaporation. Knowing that the original mixture was 3:1 "battery acid" - which I assume is a variable itself - doesn't help me now and I don't have any sofisticated equipment to measure grams/litre. Can someone relate these measurements to specific gravity which anyone can measure with a simple $3.00 car battery hydrometer? If there is a conversion formula I'd appreciate knowing it since I'd like to experiment with diffferent concentrations in my process in the future.

Thanks

[sswee]

caswellsage,
The easiest cheapest way is to measure out your electrolyte and bring the volume back to the original level mixed with distilled or RO water. The only other way to check acid concentration is titration or mix a fresh batch. I know it's not what you wanted to hear but I don't know of any other ways.
SS

[sage]

Actually this wasn't difficult at all. Sorry I asked.

I made two very small new batches of acid to the 3:1 and 2:1 ratios specified by Caswell for thier old and new LCD processes. "Battery acid" as I find out now is pretty standard at 19.2% by volume, 35% by weight H2SO4.

I then measured the specific gravity (s.g.) of the two samples with a cheap Hydrometer available at any auto supply place.

Just so eveyone is aware, the Caswell LCD solution which is a 3:1 mixture of battery acid and water and is apparently 4.8% by volume H2SO4 measures about 1075 s.g..
The original Caswell solution which I gather was 6.4% H2SO4 by volume and a 2:1 water acid measures 1100 s.g.

To back up these test results I found the data on the internet for sulphuric acid from Sulco Chemicals, an acid manufacturer. They listed various acid percentages against their s.g. The s.g measurements I made coresponed pretty closely to the percentages I new I had and their data.

Now it was a simple matter of returning my acid to the 1075 s.g by adding water which means it is back to the LCD spec of 4.8% by volume and 3:1 mixture.

Simple and cheap.

Sage

[sswee]

I didn't mean to offend. I had asked the same question when I first started and was told it wasn't an accurate way to check acid concentration. I am fixing to mix more acid for a larger tank and I'll have to check out the s.g. of different ratios.
SS