What Are Anodes Used For, Exactly?

What are anodes - 49083908490840

Have you ever wondered why large steel ships and underground pipes don’t corrode? Most metals in wet environments oxidize causing corrosion. It’s this corrosion that causes metals to breakdown, rust, and degrade.

To prevent serious corrosion, metal manufacturers will add anodes. But what are anodes?

Anodes, or sacrificial anodes, are active metals that prevent less active metals from corroding underwater. Corrosion is a natural process that causes active metals to return to their natural state, like an ore. An anode works to prevent this weakening corrosion from happening.

There is, however, much more to an anode than its negative charge and metal composition. Here’s everything you need to know about anodes work and their uses.

What are Anodes?

Metal anodes protect other metals from corroding underwater. They are highly active metals designed to corrode in place of the metals they’re protecting.

When submerged in an electrolyte (like water), all metals will produce this electrical charge. The metal most resistant to corrosion (noble metal) will act as a cathode while the metal least resistant will become an anode. The least resistant metal will start to corrode and degrade.

How Anodes Work

A boat propeller, for example, has 2 or more different types of metals. The more active metal would be the stainless steel shaft of the propellor. The least active metal is the bronze propellor.

The more active metal will corrode and degrade while the least active metal remains mostly untouched. Since we don’t want either metal in the propellor to corrode, we need to add a 3rd more active metal. This metal is the anode.

Active metals such as aluminum, magnesium, and zinc are the most popular choices for anodes. These metals have a greater standard reduction potential than metals like steel, iron, and bronze. Water will react and corrode the anode instead of the important metal components of the propellor.

Other ways of protecting important metal components of a propellor or a ship include plating, galvanization, and alloys.

About Anode Metals

While zinc, aluminum, and magnesium all work as anodes, some make better options than others. Each one has a different level of negative voltage:

  • Aluminum has -1.1 volts
  • Zinc has -1.05 volts
  • Magnesium has -1.6 volts

For the best protection, you want to use the anode metal that creates the greatest voltage difference with the metal it’s protecting. The bronze propellor mentioned above has a voltage of -0.3. Magnesium will offer the best protection as the anode will increase to -1.3 compared to zinc or aluminum.

Attaching Anodes and Where to Find Them

The anodes need to connect to the metal structure they’re protecting. Welded lead wiring and cast-m straps are the most common ways manufacturers will attach anodes. They have lower resistance and insulation to prevent damage when the anode corrodes.

You can find anodes on more than just ships. Water heaters, pipelines, refineries, and above/below ground tanks all use anodes to prevent the important metal components from corroding.

Anodes are a Necessity

What are anodes? They are vital pieces of metal designed to protect other metals from corrosion and degeneration. Without anodes, our tanks, ships, and pipes would not last as long as they do.

Want to learn more? Check out our latest Buildings articles to learn more great ways to protect structural metals both inside and outside of your home.

Interesting related article: “What is Oxidation?