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What are the Different Kinds of Metal Anodes?

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Metals commonly used as anodes include aluminum, brass, bronze, copper, lead, lithium, magnesium, nickel, silver, titanium, zinc and alloys of them. Non-metals also used as anodes include carbon, graphite and silicon. Each of these has a particular set of characteristics that make it better or worse suited for use in different devices and for specific uses. In practice, metal anodes are categorized according to how, and for what purpose, they are used. Electrical conductivity, thermal conductivity, structural strength, durability and resistance to corrosion typically are among the characteristics taken into consideration when particular metal anodes are chosen.

Perhaps the most familiar use of metal anodes is in galvanic cells, otherwise known as batteries, where an electric current flows between metal cathodes and anodes immersed in an electrolyte that carries electric current between them. Early batteries used in space missions used silver for metal cathodes and zinc for metal anodes. More recently, rechargeable nickel-cadmium batteries have been used to power many electronic devices. Iron and cadmium serve in this way. Light in weight, lithium is also used for metal anodes in rechargeable batteries that are found in portable consumer electronic devices, such as cell phones and portable computing devices. Thanks to advances in technology, lithium also has been used for anodes in lithium ion batteries to power hybrid and all-electric vehicles.

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Another common use of metal anodes is to protect metals or other materials from rust or corrosion. For example, sacrificial and offshore sacrificial anodes, which are also known as galvanic anodes, are meant to protect a cathode, typically another metal that needs to be preserved for as long a period as possible, from rust or corrosion. The anode is made from a metal or alloy that corrodes more easily than the cathode. Such is the case with zinc and iron, where zinc, or a zinc alloy, is layered on top of the iron.

With exposure to the elements — air, saltwater or freshwater — oxidation will occur, and electrons will move from the sacrificial anode, the zinc or alloy, to the iron, protecting it from oxidation. By definition, this makes the iron a cathode. Another example of this is the hot water heater anode, where one or more rods of magnesium or aluminum are layered around a steel core, protecting it and the metal outer casing of the tank from the rust or corrosion that would result from regular contact with heated water.

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submariner
Post 4

@Alchemy- Rust protection is big business in the United States. Preserving infrastructure, vessels, and historic buildings is vital to preserving history and reducing infrastructure costs. Corrosion results in about $300 billion in direct costs every year, making corrosion abatement a huge economic sector. Entire engineering fields are devoted to finding ways to prevent the built structures in this country form corroding away. Corrosion also affects a number of other materials besides metals. Plastics and glass corrode through oxidation, albeit at a slower rate than metal.

@aplenty- Metal Electroplating can be used to prevent rust, abrasion, and improve the aesthetics of metal. There are a number of electroplating processes, but the most common is similar to some of the techniques presented

below. The process works by making the part to be coated the cathode, electrifying a sacrificial anode to plate the cathode with, and placing all of these materials in an metal ion electrolytic solution. The electrolytic solution filled with metal ions allows the ions from the anode to transfer to the cathode, resulting in a eletroplated finished product. The most important part of the process is to make sure the part you re plating is clean. You should clean the metal by electrochemical or acid bath processes to ensure that the plating will adhere to the metal.
aplenty
Post 3

What is the relationship between metal anodes and metal electroplating? I would like to learn how to electroplate metal so I can make custom bumpers and hitches for off road vehicles. I already know how to weld, but I do not know how to electroplate metals with corrosion resistant materials.

Fiorite
Post 2

@Alchemy- The most common anode metal used in ship building is zinc because it is cheap and more electronegative than steel. If you ever looked at a ship in dry dock, you would see that the ship has anodes bolted onto the ship's hull. Anode corrosion protection also works with other metal objects. Buildings, bridges, and other land based structures use sacrificial anode protection to preserve them from the elements. This technique is especially common in historic structures like lighthouses.

If the structure is especially large, a technique called impressed current cathode protection (ICCP) is used. IPCC is the same as sacrificial anode protection except that a direct current power source is connected to the anodes to provide greater coverage

with fewer anodes. Without IPCC, sacrificial galvanic anodes would not be economical for large applications.

The reverse process to cathode protection is anodic protection. This is the process where a current is applied to the cathode (the structure) to protect it from corrosion in extreme environments. This technique might be used to protect steel vessels that are used to store highly acidic materials like sulfuric acid. It is also used in industrial processes where caustic materials come in contact with equipment.

Alchemy
Post 1

I never knew that anodes could be used to prevent corrosion, but it makes total sense. On steel, what anode material is the best for preventing rust? For example, what type of sacrificial anode would one use for protecting the hull of a steel ship from rust?

I always wondered how steel ships did not rust in sea water, especially considering they remain in the water for two to three years between being dry docked. I can only imagine how expensive it would be to keep the giant ships of our day afloat if it were not for electrochemical processes. Ships would probably still be built from wood, or they would be built from some expensive, but non-reactive material like copper alloy.

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