See It Protect!
Stops The Steel From Rusting!
In order to show you just how the sacrificial anode rod works, I've assembled a demonstration to illustrate the idea of cathodic protection and its effects. It's difficult to imagine that the idea of simply mating two metals together in a container of water will have any sort of positive and meaningful real world impact on our own household water heaters. However, to show you just how well this idea works and how bad the alternative is, the following information is provided to model this concept. This will give you a solid visual on just how the anode protects your tank.
I fabricated these models to represent the steel wall in your water heater, both in an unprotected and a protected-by-a-sacrificial-anode state. Picture #1 contains a piece of steel plate all by itself and unprotected. Picture #2 contains a duplicate piece of steel that is electrically connected to a magnesium anode just to the right of it. Both are filled with tap water and left out at room temperature.
The following pictures are of the exact same samples after they've been sitting undisturbed for just 24 hours - the results are actually quite shocking.
The steel plate in picture #3 is already experiencing a significant reaction. The water is quite discoloured from the corrosion and there is a lot of rusty sediment accumulating at the bottom of the jar.
The steel plate in picture #4 appears to be experiencing no visible signs of corrosion and looks much like it did when it went into the jar. However, the magnesium rod is already showing significant corrosion of its surface and the water remains clear.
In an attempt to mimic the experience of a water heater, about half of the water was removed and replaced with fresh water each day, just like your water heater experiences an influx of fresh water in daily use. This will ensure the reaction remains active.
Pictures #5 and #6 are taken after 4 days of submersion. Significant sediment is shown in both jars. The sediment in picture #5 is obviously corrosion of the steel plate, while the sediment in picture #6 is corrosion from the sacrificial anode. Either way, this illustrates the importance of flushing and draining your tank as sediment will tend to accumulate in both a protected and an unprotected water heater.
Please note: Because of the light source I'm using, I've changed the orientation of the subjects in an attempt to better illuminate all the surfaces and provide an improved viewing angle.
In the next photos, I've removed the metal assemblies from the jars to provide a clearer view of the affected surfaces without the distortion of looking through the glass jar and the water. Once again, this is after just 4 days of submersion.
Picture #7 provides a good visual of the corrosion being experienced by the steel plate all by itself and that of the anode as it protects the steel plate it is attached to.
Picture #8 is a shot of the two jars as seen from below to show the sediment that has accumulated in them both. The jar at the top of the photo exhibits the corroded particulate from the reaction of the steel plate. The jar at the bottom of the photo displays the corroded remains from the magnesium anode.
You can certainly see that the use of a sacrificial anode has a huge impact on protecting any exposed steel surface it is connected to. The unprotected steel is being corroded while the protected steel shows no such signs, however, the sacrificial anode is definitely deteriorating while doing its job.
We performed one last test to see if the anode has any affect on a piece of steel that has already been corroded. We attached our rusty sample to our anode fixture and placed the assembly back in the jar of water once more.
Picture #9 is taken as soon as the assembly was placed into the jar of water. Picture #10 shows the same assembly after 4 days of submersion. There appears to be no further corrosion of the previously rusted steel, and the magnesium anode is once again reacting as it works to protect the steel plate. As there is no rusty sediment or orangey discoloration of the water, It appears that the corrosive reaction of the steel plate has been stopped or at least slowed down considerably courtesy of the sacrificial anode.
This is a compelling example that attests to why most manufacturers install sacrificial anodes and indicate in their literature that an active sacrificial anode rod must be kept in your tank. It is there to protect the inside of your water heater from such devastating corrosive action and prolong its operational life. The manufacturers know it and now so do you!
Ultimately, it would be far, far better to spend a little on replacing the anode now and significantly increasing the life of your water heater, than to have to replace the entire unit prematurely.