Cell cleaning schedule.

[chem geek]

My thought process is that the soultion will deteriate the cell a bit as well so if I don't see any build up then there is no need to clean... Anyone else have a cell that does not need cleaning very often ?

Unless the guys who wrote the instructions on how much you should dilute the acid for an acid wash were idiots, they should have the solution diluted enough (but not too much) so that it will readily dissolve calcium carbonate scale while having virtually no effect on the titanium (or titanium coated with various substances) blades.

As an aside, the calcium carbonate scale builds up on the blade that is highly basic, namely the blade that is producing hydrogen gas from the following reaction:

2H2O + 2e- --> H2(g) + 2OH-

It is the high alkalinity of this reaction that causes the calcium carbonate in the water to precipitate out of solution and onto the plate (shouldn't happen in a vinyl pool since you don't need much calcium in the water in that situation). The reversal of polarity moves the problem to the other plate while causing the following acidic reactions to occur at the original (now reversed in polarity) plate:

2Cl- --> Cl2(g) + 2e-
Cl2(g) + H2O --> HOCl + H+ + Cl-
----------------------------------------
Cl- + H2O --> HOCl + H+ + 2e-

Under these acidic conditions, any scale buildup should dissolve. So the secret is switching back and forth between the plates fast enough to prevent scale but not so fast as to degrade the electrochemical reaction efficiency.

The only reason for the periodic dipping in acid is that this polarity reversal is not perfect and some scale could potentially build up in spite of the best efforts. All it would take is for the calcium carbonate to adhere just a little more than it dissolves when reversed and you could get a net buildup. Technically, you can see that the basic process is more strongly basic (alkaline) than the acidic process because HOCl is a weak acid so the formation of scale could conceivably occur faster than the dissolving of scale. Also, additional substances (such as metals) could conceivably be changed from a dissolved ion into a solid metal at the plate and will need to be dissolved by acid though a good design of the voltages used in the cell can minimize this effect.

Richard

[Phillbo]

why does my head hurt everytime Richard replies to one of my post


so, dip it when I see build up. otherwise leave it alone.

[Pool_Mike]

why does my head hurt everytime Richard replies to one of my post

I learned that Richard is a PIMP of the POOLS, and that is why I feel like a slut that cannot understand my pimp

[rpoldervaart]

Does anyone have a picture of the build up on the cell? Mine 9 months old and the clean line has come on a couple times. I've cleaned it each time, but am not sure if it had anything on it or not. Where do you see the build up?

Thanks,
Robert