zinc sacrificial anode

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T

trbvm

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Jun 8, 2015
216
Phoenix, AZ
moderator Note. Moved from this thread:. zinc sacrificial anode

Old thread... but relevant to my question :)
I am putting in an 'inline' sacrificial anode just like the one below:
XCxPPGU.jpg


The manual says put this between the filter and the heater. But, I don't have much space there.

Can I add this just after the pump - and before the filter? I have space there.
 
It is not necessary to put the anode into the water flow as that will add zinc ions into the water. You can instead place a zinc anode in moist soil (acts as a ground source for electrons and a sink for zinc ions) and just electrically connect it to the bonding wire. The idea is to put a small negative voltage onto the metal that is in contact with pool water. That makes it harder for positive metal ions to form (increases the potential that must be overcome for corrosion to occur).
 
chem geek said:
It is not necessary to put the anode into the water flow as that will add zinc ions into the water. You can instead place a zinc anode in moist soil (acts as a ground source for electrons and a sink for zinc ions) and just electrically connect it to the bonding wire. The idea is to put a small negative voltage onto the metal that is in contact with pool water. That makes it harder for positive metal ions to form (increases the potential that must be overcome for corrosion to occur).
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I actually thought about this, chem geek. But, here, in AZ it is difficult to rely on 'moist' soil. Everything is bone dry... well, except for some flowers in the front yard. We have xeriscaped everything. Also, I was worried about the scaling on the zinc diminishing its effectiveness.

In this setup, I can see the zinc through the glass and sandpaper it if it gets scaly.

BTW, since I am putting it between the pump and the filter, will the DE filter get some of the zinc out? I assume it will not, right, since the zinc is going to be small (atomic size)?
 
That puck one will do absolutely nothing to protect other metal in the pool because it is not electrically connected to that other metal. Think about it. Zinc corrodes more readily than the other metals in the pool, but what exactly is preventing the other metals from corroding at the same rate as they were before you added the zinc? Nothing is preventing that.

If you were to electrically connect the zinc to the bonding wire to other metals in the pool, then the zinc will impart a small negative voltage onto the other metals which will slow down their corrosion rates by increasing the potential that must be overcome for an ion to leave the metal (because the positive ion is attracted to the now more negatively charged metal).

Though I generally hate referring to Wikipedia because it is sometimes wrong or incomplete, in this case in the article on Galvanic anode it is mostly correct when it says:

For this to work there must be an electron pathway between the anode and the metal to be protected (e.g., a wire or direct contact) and an ion pathway between both the oxidizing agent (e.g., water or moist soil) and the anode, and the oxidizing agent and the metal to be protected, thus forming a closed circuit; therefore simply bolting a piece of active metal such as zinc to a less active metal, such as mild steel, in air (a poor conductor and therefore no closed circuit) will not furnish any protection.
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While they are correct about needing an electron pathway (i.e. electrical connection), the ion pathway need not be complete if there is an effective sink or source for ions due to the large volume of soil or water and a continual flow and dilution of such ions. It's similar to how ground (moist soil) is a source and sink for electrons.

As for putting the zinc sacrificial anode in the pool water (electrically connected to the bonding wire), the zinc ions are not likely to stain since not that much zinc is expected to be added and zinc oxides/hydroxides are more soluble than those of copper and (ferric) iron. At a pH of 8.0, the solubility of zinc hydroxide is over 500 times higher than that of copper hydroxide which is over 500 billion times higher than that of (ferric) iron hydroxide (it's very insoluble).
 
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