Quick review (if you want it)…

All types of water are considered an electrolyte solution. All metals are susceptible to corrosion when placed in an electrolyte solution. Stray current leakage will increase the rate of corrosion. The relationship between dissimilar metals in this environment is relative. The metal with the lower atomic number (check out a periodic table if that is something you didn’t retain from high school) will become the anode in this relationship, and the metal with the higher atomic number will become the cathode. The anode sacrifices itself to keep the cathode intact.

You want to a Martyr sacrificial anode to sacrifice itself instead of an important metal piece of your boat! But which one is best for your boating environment, Aluminum, Zinc or Magnesium? (Check out WEEK #5 to review which anode is best in saltwater). Today we will tell you about brackish and freshwater.

Just in case you don’t know, brackish water is a combination of saltwater and fresh water. This is typically found in bays or harbors that have fresh water rivers running into them, or in tropical coastal areas where there is a lot of rainfall that runs into the ocean. So, let’s talk about brackish water first…

Aluminum responds best in brackish water, because brackish water has a lower salinity than saltwater. Since the salinity (salt content) in brackish water is lower, the metal anode can be “weaker” (have a lower atomic number) and still have the same ability to protect your boat because the water around it is also “weaker” in reference to electrical current.

Aluminum has also become very popular because it is a lighter metal, making it easier to ship, which in turn typically makes it cheaper than its zinc and magnesium counterparts. Another great thing about aluminum is that it is the most environmentally friendly anode of the 3 that can be used to protect your boat.

Magnesium has the lowest atomic number of the 3 options. Following the same thought process as above, that makes it best in fresh water, which has the lowest salinity of the 3 water types. If you were to try to use magnesium anodes on your boat in saltwater instead of zinc or aluminum you would have to change your anodes 3 times as often to protect your boat.

We want you to get the most out of your anodes and to protect your boat in the best way possible, so remember this…




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