Sacrificial Zinc Or Magnesuim Anode

[rocket]

Can someone give me a link to exactly what I need to buy? Or give me the exact name? I have seen several anode type things, but don't know which one is the anode that gets attached (connected electrically) to the bonding wire and then buried in moist soil.

thanks

[quantumchromodynamics]

Here are some references:

http://www.pooltool.com/index.php

http://www.pooltool.com/44413Catalog.pdf

http://www.pooltool.com/catalog.php

Without knowing your exact situation, I can't advise you on what to do. If this is a new pool, then this is not something you should have to deal with.

This is something the pool builder needs to make right. I don't think that an anode is necessarily the best solution. You need to find out why this is happening and not just try to mitigate the damages.

[rocket]

I know it is because my water levels were way off. I had high FC and low PH and CA. Just getting it in case they fall off again. Will get a taylor test kit next year to keep track of them myself. After filling the pool (had to partially drain after they added to much salt first time) they came and got a water sample. And next day they came out with chemicals to add. However they just left the chemicals and did not add any when I thought they did. Girl at there office thought they did as well. Person dropping them off later said he didn't. (seems stupid to not add them while he was here) . So my pool sat about a week with high FC and next to nothing of CA and low PH, which I believe caused the corrosion of the skimmer screws (pool guy said he will replace them all). I already have a zinc thing in my skimmer but want to do the attached one to bonding wire buried which most people here say actually works. Should I just replace the screws and maintain the water and see if it does it now that the water levels are correct?

[chem geek]

Just for clarity, the "CA" you are referring to was Cyanuric Acid (CYA), not Calcium Hardness (CH).

I would remove the zinc from the skimmer. There is no reason to put more metals in your pool. Just take the zinc out of your skimmer, bury it in moist soil, and attach it electrically to the bonding wire. It may not be necessary, but since you've already got the zinc it's something you could do if you wanted to. Of course, you could just replace the screws and maintain the water properly and you should be fine even without the zinc anode.

[jkusmier]

No need to buy/order a magnesium anode from a pool store. You can google search "magnesium anode" and find something probably intended for a boating application. Works just the same, and probably cheaper. Connect it to the bonding wire w/ 8 gauge copper wire (not 8 gauge audio copper wire) and bury it near your equipment pad.

[rocket]

No need to buy/order a magnesium anode from a pool store. You can google search "magnesium anode" and find something probably intended for a boating application. Works just the same, and probably cheaper. Connect it to the bonding wire w/ 8 gauge copper wire (not 8 gauge audio copper wire) and bury it near your equipment pad.

Pool guy is buying it and installing because trying to make up for corrosion I have. So I don't care what it costs just want a link I can send him to on the web so he can buy and install it just to be safe in future.

[jkusmier]

I found mine by doing a google product search for "magnesium anode boating" or something like that. They come in all shapes and sizes, shape is inconsequential. I recall paying ~ $15 w/ shipping. West Marine is a very dependable source, but there are plenty of others.

[rocket]

Says here for boats anyway that magnesium over protects and can cause damage and problems.

http://gulffishing.com/tips_anode.html

[chem geek]

The over-protection and problems they are talking about are where the higher net electron charge on the other metals can cause hydrogen gas to form. The amount in a salt pool, as opposed to the far higher salinity of the ocean, will be much smaller and probably not an issue since there usually aren't painted metal surfaces exposed to the water and the pump is on every day to circulate water against those metal surfaces. Again, in your situation you had bad water chemistry so an anode may not be needed at all. If you felt more comfortable using zinc, then as the galvanic series showed, that should be fine.

[rocket]

Is this want I want? (they have lots of zinc anodes to choose from)

http://www.pooltool.com/

It says for the item description.

The inline zinc anode is attached to the bonding wire thereby protecting all metal parts against the effects of electrolysis. Available in 1-1/2” and 2”. The see through housing allows the anode to be easily replaced when depleted. No replumbing required. A must for salt water pools. Replacement Anode (No. 104 C-1)

[chem geek]

I don't understand why this is "inline" and seems to be exposed to the water. Normally, you just attach the sacrificial anode to the metal to be protected so in this case to the bonding wire. The anode itself doesn't have to be in the pool water and it's better if it isn't because it will corrode zinc into the water and that could eventually stain. You just want the anode buried in moist soil though technically not doing that still works, just not nearly as effectively. The only purpose of the zinc anode is to force electrons towards the metal surfaces to be protected. You could place a voltmeter between your sacrificial anode and the bonding wire to see that there is a potential difference that is measured (negative terminal to the anode; positive terminal to the bonding wire).

[rocket]

Would any of the other ones work on that site? Does anyone know what/where to buy? I know that since I got my water levels straightened out I could just wait and see what happens, but I would rather add it now while the pool guy is willing to do it and pay for it.

[jkusmier]

Richard, I might be wrong but I looked at this anode (104C) when searching for an anode for my own pool. I don't believe it's exposed to the pool water, it just mounts atop the plumbing and is clipped onto the bonding wire. The one at the bottom of the page (104D) is definitely exposed to the water. I passed because I wanted a magnesium anode.

[chem geek]

I can't tell looking at it but it's odd to mount it on the pipe if it wasn't drilled through.

[jkusmier]

I can't tell looking at it but it's odd to mount it on the pipe if it wasn't drilled through.

Agreed - I think the mfr believed placement above ground and on plumbing at the equipment pad would be more visible (not a bad idea) and that customers could see the product was doing what they paid for. Hence the price! I may call them tomorrow to confirm - Richard, I'm curious now.

[rocket]

I can't tell looking at it but it's odd to mount it on the pipe if it wasn't drilled through.

Agreed - I think the mfr believed placement above ground and on plumbing at the equipment pad would be more visible (not a bad idea) and that customers could see the product was doing what they paid for. Hence the price! I may call them tomorrow to confirm - Richard, I'm curious now.

jkusmier what did you find out? Can you buy directly from Pooltool or do you have to buy from one of their distributors?

[jkusmier]

Sorry, I haven't had the time to call Pooltool, but you certainly should. I'm pretty sure it's merely mounted atop the plumbing and not actually exposed to pool water.

You can definitely order from retailers instead of ordering direct from Pooltool, see this google products search.

[rocket]

I called and secretary did not know answer. The boss in on vacation till Monday.

I could take the one out of the skimmer basket and attach to bonding wire and bury, but don't they need replaced when they are used up? How often would you have to dig it up to replace it? And how would you know it was time without digger it up? How deep should it be buried?

[chem geek]

Good questions for which I don't know the answer. I'd guess that you need to check it at least once a year, but initially you could check it more frequently until you get some idea of how quickly it is degrading. It doesn't have to be deep -- just have some in moist soil similar to what you would do with a grounding post. You basically want the zinc that becomes ions not to build up too much next to the anode and moist soil helps to carry them away while the earth overall provides a good sink for the electrons (i.e. a "ground").

[rocket]

I think I am going to stick with zinc. Found another thing about magnesium

http://www.amteccorrosion.co.uk/cathodic.html

I have powdered coated hand rails. In the above article it says manesium can cause coating to peel or something.

Best price I found for the inline anode is $75. here.

http://baxtersdesignerpools.com/home/index...1&Itemid=31

I may call them about whether it touches the water.

What do you think of this system?

http://baxtersdesignerpools.com/home/index...1&Itemid=55

[quantumchromodynamics]

the earth overall provides a good sink for the electrons (i.e. a "ground").

The electrons do not go into the ground; they go to the cathode.

At the anode, an oxidation reaction occurs:

6(Zn)(s) --> 6(Zn)+2 + 12e-

The zinc can then combine with water to form zinc oxide. The electrons go through the wire to the cathode where the following reduction reactions occur:

12H+(aq) + 12e− → 6H2(g)

and

3O₂(g) + 6H2O(l) + 12e− → 12OH−(aq)

The metal cathode is protected because the hydrogen and oxygen are getting their electrons from the anode, instead of the cathode. Without a steady supply of electrons, the oxygen would combine with the metal (Let's use iron) like this:

2O2(gas) + 2H2O(l) + 4Fe(s) --> 2(Fe2O3) (aka iron oxide or rust) + 2H2(g)

(Essentially, anything that would oxidize the iron is reduced by the electron supply from the anode.)

Any iron that is oxidized can be reduced back to solid iron by the supply of electrons from the anode.

Fe3+(aq) + 3e− → Fe(s)

You can increase the potential difference between the anode and the cathode with a DC power source that will pull electrons from the anode and push them to the cathode. This is called a Powered Anode or Impressed Current Cathodic Protection. In the case of a powered anode, the anode does not degrade because the anode is not supplying the electrons; it is pulling them from the environment. In fact, this is what's happening inside the salt cell. You have a powered anode and a powered cathode, which, theoretically, should cancel each other out.

Note the production of hydrogen gas and hydroxide at the cathode. If you overpower the cathode, there will be excessive hydrogen gas and hydroxide produced.

There is no need for the anode to make contact with the pool water. There is no complete circuit that the electrons make. It is more of a "theoretically" complete circuit like in the salt cell. In the salt cell, electrons are pushed out of the cathode and pulled in from the anode, but they are not the same electrons; but the cell power supply doesn't care as long as it gets back the same number of electrons that it put out.

[quantumchromodynamics]

I think that all you need is a suitable mass of zinc connected to the bond wire. I don't think that it needs to be buried in the ground. I also don't see any reason for the zinc to touch the water. You should measure the voltage between the zinc mass and the bond wire upon installation, and periodically thereafter, for reference.

Note: Do not cut the bond wire. Attach one end of a # 8 bare solid copper wire to the bond wire with an electrical split bolt and the other end to the zinc mass by whatever means will give a good solid connection.

[chem geek]

The electrons do not go into the ground; they go to the cathode.

Yup, I knew better but had a brain fart (so to speak). Thanks for correcting me.

So if the zinc were just held in water (not pool water, but a separate container) like the product showed, wouldn't the buildup of zinc ions cut down the voltage pushing the electrons towards the bonding wire and protected metal? In order to continue to provide a higher voltage wouldn't the zinc ions need to be diffused away? Otherwise, the buildup of positively charged ions would keep the extra electrons closer to the zinc than to the metal to be protected. Does that sound right?

[quantumchromodynamics]

I think that the positively charged zinc ions should combine with available negatively charged ions, such as oxide, chloride, sulfide, carbonate etc. to become neutral zinc oxide, zinc chloride, zinc sulfide, zinc carbonate etc.

I think that as long as the container was not sealed and was open to the air there would be sufficient water from the air to allow zinc oxide to form until the anode was completely used up. Perhaps there is a small hole in the pipe or container that allows air or water in.

I don't think that there is any need for any special expensive devices or equipment. I think that just a plain mass of zinc should suffice.

[rocket]

1st. I called the company above and they said the inline anode pictured above does touch water. You drill a hole in your PVC pipe that it is attached to and the zinc touches the water there. Also it is attached to the bonding wire. Having the zinc contact the water like this, is that bad?

2nd. Also, what happens to the zinc as it get's used up? If buried would it go into the ground at that spot? If you changed the anode every year wouldn't that small spot in the ground have a dangerously high level of zinc?

3rd. Does the anode protect any metal that is not in the water (above water line)? My electric cover aluminum rails are above the water line. Would the anode help protect them from corroding? I guess want I am asking is what will the anode actually protect other than my skimmer/light screws. My hand rails are not in the water nor is my cover. My heater is made of titanium inside.