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Author Topic: Anode rod replacement - aluminum vs. magnesium  (Read 10687 times)
Camping Queen
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San Clemente, CA


« on: July 24, 2009, 07:37:00 AM »

While doing a search to replace the anode rod for my Suburban SW6P water heater, I see that PPL offers them in both aluminum and magnesium.  The difference is less than $3 for the magnesium.  So is there any advantage?  Performance, length of use, etc?  I appreciate any insight you all may have.
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Jane -'6?  Deleware         
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« Reply #1 on: July 24, 2009, 07:50:26 AM »

When I was in the Navy, we always used zinc anodes for corrosion protection (bilges, etc). 

The anode in my water heater sure looks like zinc to me.  Never heard of using Al or Mg.

I need to look into a new one myself.  '02 Bayside that's still on the original anode.  Its about a 1/4 eaten away last I checked.

Kevin
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Kevin
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hoppy
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« Reply #2 on: July 24, 2009, 08:36:39 AM »

 I just did a quick check on the net regarding this topic, since it aroused my interest.
What I found is both aluminum and magnesium are used as the sacrificial material for anode rods.

 A aluminium anode can be identified by a flat surface on the face of the hex nut, while a magnesium anode will have a bump on that surface. The article goes on to say that in marine use, often the material is zinc.

 On one of the sites, this writer recommended using the magnesium material over aluminum for several reasons:
 First, aluminium being lower on the Galvanic Scale than magnesium produces less driving current between the anode and cathode. (tank being the cathode) They believe that this means aluminum doesn't do as good a job protecting the tank sides as well as magneisum.
 Second, it produces about a thousand times it's original volume in corrosion byproduct, which falls to the bottom of the tank in the form of jelly and sediment buildup.
 Third, this jelly can pass out of the tank causing filters, water lines, and aerators to clog.
 Fourth, aluminum can expand to the point it can not be removed out of the heater after a few months. I personally don't see this happening with my water heater, but this article was based on home water heaters.
 Fifth, aluminum has the tendency to split from the core wire, and now becomes solid junk rather than an anode.
 Sixth, the heater may become noisy due to chunks of the aluminum anode bouncing around during the cold water refill.
 Seventh, food contamination by aluminum.

 There you have it...May have been written by the Magnesium Corporation of America as far as I know.   
« Last Edit: July 24, 2009, 01:01:20 PM by hoppy » Logged

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Tukee44
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« Reply #3 on: July 24, 2009, 11:07:52 PM »

So I suspect the original rod that came with the water heater was probably Aluminum.
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hoppy
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« Reply #4 on: July 25, 2009, 02:19:23 PM »

So I suspect the original rod that came with the water heater was probably Aluminum.

 When I bought my 2001 Mesa used back in 2003, the anode that I removed and replaced was magnesium.
 Not knowing any better, I just replaced it with an aluminum one back then, and subsequently another aluminum one three years ago.
 My anode is due to be changed out soon, (probably by the end of the summer) and it will be replaced with a magnesium one this time.
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Camping Queen
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« Reply #5 on: July 25, 2009, 05:54:36 PM »

Sounds like there's a negligible difference in price, but a substantial difference in performance - I'll be ordering a couple of magnesium ones tonight.  Thanks everyone!
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Jane -'6?  Deleware         
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ballard
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« Reply #6 on: July 26, 2009, 05:40:45 AM »

I have had problems with odors related to my home water heater due to the hard water. In researching I discovered this (see quotation below).

"Hydrogen sulfide is formed by sulfur bacteria that may occur naturally in water. These bacteria use the sulfur in decaying plants, rocks, or soil as their food or energy source and as a by-product produce hydrogen sulfide. The sulfur bacteria do not cause disease, but their presence in water can cause a bad taste or odor.

Water heaters can also be sources of foul odors stemming from hydrogen sulfide. A magnesium rod is often placed in the tank by the manufacturer to prevent water heater corrosion. Sulfur that is dissolved in water can react with the magnesium rod forming hydrogen sulfide. The magnesium rod can be replaced with an aluminum one or removed completely. Removal however, may void the company's warranty."

-Mike Miller
Karen Mancl
Ohio State University Extension Fact Sheet
Food, Agricultural and Biological Engineering
590 Woody Hayes Dr., Columbus, OH 43210
« Last Edit: July 26, 2009, 06:12:36 AM by ballard » Logged
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