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What is galvanic corrosion?

Mar 02, 2018

The scientific definition of galvanic corrosion describes it as an electrochemical process in which two different metals or alloys are electrically contacted in the presence of electrolytes, resulting in relative corrosion of contact materials.


Corrosion of iron is the most common example of galvanic corrosion, in which the core steel is attacked and the protective coating of zinc is damaged. Zinc is not noble, vulnerable to galvanic attacks, once completely extinct; On the other hand, tin is more noble than core steel, making it harder to break, but when it does, the bottom steel suffers the worst.


The mechanism behind galvanic corrosion


Galvanic corrosion can occur only when two different metals and alloys have different electrode potentials. The less noble metal forms the anode, while the noble metal takes the cathode position. The difference in electrode potential accelerates the anode attack, which is later dissolved into electrolytes, collecting sediments on the cathode, in this case metals.


The electrolyte initiates the migration of ions from the anode to the cathode, which causes the anode metal to corrode rapidly while suppressing the corrosion effect of the cathode metal. The availability of electrolytes ensures that ions remain migrated to allow galvanic corrosion to occur.


Although this is not an ideal process, it has several applications. In the main battery, it is intended to provide a carbon zinc battery to promote the preferential corrosion of the zinc producing voltage. Another application is to preserve the buried structure by cathodic method, and the anode material is corroded to inhibit the corrosive action of cathode metal.


How to prevent galvanic corrosion


The best way to avoid contact between two metals and alloys is to do the same electrical insulation. You can use non-conductive materials, such as glass, rubber, or plastic, between metals with different electrode potentials. For pipes with aluminum rods, you can use a roll of plastic tubing to coat the interior.

Electroplating technology can be used where precious metals such as silver, gold or nickel are used to form anodes. 316 stainless steel stud can be used as sacrificial anode by galvanizing.

Metals with similar electrode potentials or at least close to each other are less likely to form a pair of galvanic pairs. Using similar metals for various production is the easiest way to match electropotentials.

Galvanic corrosion cannot occur without electrolyte. You can use grease or oil painting to remove the chance of contacting the electrolyte. In the case where it is not feasible to provide a coating of metal, a coat of a more noble so that when corrosion occurs, there will be a smaller anode area that suffers the greatest corrosion effect.


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