Magnesium anode vs Electric anode vs No anode

ethicalpaul · June 18

What can this experiment teach us? Possibly not much!

https://www.youtube.com/watch?v=YAUKRCdN1y4

mattmia2 · June 18

the floating stuff is magnesium hydroxide from the anode(or other salts of Mg depending on what is in the water). the iron in the water probably plated on to the steel pipe from the mg-fe cell

when you concentrate the minerals in the water by evaporating and adding more you increase the conductivity of the water so more current flows in the powered anode (probably limited by the power supply) and the Mg anode dissolves a lot faster from the hinger current and the unprotected pipe rusts faster.

mattmia2 · June 18

the iron only one isn't oxidized on the submerged surface but the surface is gone, it is raw iron where you piped it and that black stuff you dumped out is some oxidation state of the iron that dissolved. I think there is some iron in the water to begin with but not that much.

i think the black pile under the anode is particles of Mg metal coated in Mg oxide. The Mg hydroxide i believe is a slimy, white, cloudy gel that is slightly to somewhat soluble in water. If you add a lot of water it will dissolve, with a little water it forms a slimy precipitate.

ethicalpaul · June 18

thanks! I probably should have been draining the whole time but then it would be hard to see the oxides

mattmia2 · June 18

Could have topped it up with distilled or deionized water. Probably could cover it some, i think evaporation happens a lot more readily than absorbing oxygen so it wouldn't take a lot of air exchange to keep the same oxygen level in the water.

Could out a resistor between the anode and the steel. or a resistor and pot in series so you could measure across the resistor to figure out the current and adjust the pot to keep the current small.

hot_rod · June 18

Interesting demo.

Corrosion does increase with water temperature quite a bit. So the tank would see increased potential compared to the buckets.

Not much ryst in the mag rod bucket?

Do you have a test on the town water to see what is coming into your home? That seems like a lot or iron settling out of a small quantity of water?

Do I see a removed breaker panel cover in the background 😉

hot_rod · June 18

Patenia is the term ued to describe the film of minerals that form on a pipe or tank. This coating served to protect the underlying metal. Similar to anodizing a piece of aluminum to protect it.

One of the ingredients in a hydronic conditioner is a film provider that puts a thin coating on all the new metal surfaces to help prevent their corrosion.

mattmia2 · June 18

https://forum.heatinghelp.com/discussion/comment/1858111#Comment_1858111

my guess would be that about 10x that much water has been added over 6 months of refilling it. if the water has been sitting in the ci main or galvanized pipes it probably has picked up some iron.

ethicalpaul · June 18

no, it wasn’t that much makeup. It’s a basement after all. I estimate over the whole duration I might have added a couple gallons to each bucket.

I wanted fresh water added to it so that I would see rust formation.

Yes the mag anode bucket was crystal clear the whole time. The “no anode” bucket had by far the most rust.

I am aware a water heater has hotter water in it than a bucket does 😅 I would have liked to have it hotter because of the increased corrosion, but I have constraints

Do you have a test on the town water to see what is coming into your home? That seems like a lot or iron settling out of a small quantity of water?

I think some of it must have been forming on the pipes, but I don't actually know.

mattmia2 · June 18

With the Mg Fe cell, the current is going to deposit the iron in the water on to the iron electrode, the pipe. It takes very little iron in the correct oxidation state to be orange to dye the water orange although that looks to be in an insoluble state. A toilet tank starts to get that type or precipitate pretty quickly. It may be in a clear and soluble oxidation state until it gets better contact with air where it changes to an insoluble orange oxidation state.

ethicalpaul · June 18

thanks Matt! That matches what I saw here.

hot_rod · June 18

Looks like you used all black steel nipples? on purpose I suppose?

I often wonder how a tank that is completely lined with glass, including the welded on connection points, rust, or need anode protection. Plastic or composite tanks don't have anodes that I know of.

Most stainless tanks do not either.

ethicalpaul · June 18

I did use so-called black steel pipes (honestly I don't know why they call them that…they are just steel as far as I can tell)…what kind should I have used?

I have heard people say that the glass lined tanks are really more of a baked on enamel that is prone to cracking.

My favorite tank I've ever seen is the Rheem Marathon (plastic)—I wish they offered that as a heat pump unit.

Magnesium anode vs Electric anode vs No anode

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