Reasons For Galvanic Corrosion Of A Hex Bolt And Its Prevention

By Author: Sidharth Jain
Total Articles: 32
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Galvanic corrosion which is also called contact corrosion or bimetallic corrosion is an electrochemical process in which one metal corrodes originating from another metal. This process takes place when either two metals or a combination of the alloy come in an electrical contact also in the presence of an electrolyte.

The process of galvanic corrosion occurs when two or more various types of metals or alloys having varying electrode potentials interact with each other. The less refined materials produce the anode, while refined materials create the cathode. The variation in electrode potential stimulates the attack on the anode, which later gets diffused in the electrolyte and coats are accumulated on the cathode, which in this case, is a metal.

The electrolytes target the immigration of ion from the anode to the cathode, which makes the anode to rust promptly while restraining the impact of rusting on the cathode side. Availability of electrolyte ensures that the ions keep migrating in order to allow the galvanic corrosion to take place. However, you can prevent that in an effective manner.

How to Prevent ...
... Galvanic Corrosion in a Hex Bolt And Other Fasteners?

The electroplating techniques can be used, in which the refined metals such as gold, nickel or silver is used to make the anode. The stainless steel fasteners can be preserved through coating them with zinc, which is used as an anode.

Choose such pair of metals which have similar electrode potentials or at least near to each other. Because such pair is less likely to create galvanic corrosion. Using such pair of metals for all kinds of manufacturing are the easiest ways to balance the electro potentials.

The best way to avoid the contact between two metals or alloys is to do an electrical insulation of the metals. In this process one can use non-conductive materials such as plastic, glass or rubber in between the materials of different electrodes. For piping with aluminum rods, one can use a roll of plastic pipe to coat the interior.

Galvanic corrosion is not able to take place in the absence of an electrolyte. You can employ greasing or oil-painting of metals to eliminate the chances of contact with an electrolyte. In case it's not feasible to provide a coating to both the metals, coat the one which is nobler so that when the corrosion takes place; there will be a smaller anode area suffering the maximum effect of corrosion.

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