Why you should never just go ahead and use different metals in the same construction
Corrosion is the destructive attack of materials by their environment. How does it develop? Why is it so dangerous for structures?
The most common form of corrosion is rust which develops as a result of iron being exposed to oxygen and water vapour in the air. Iron forms a compound with oxygen and transforms into the hated red-brown substance. Corrosion can also develop when two different metals come into contact with each other: this is known as galvanic corrosion. Our specialists explain how it develops.
Corrosion of pipes
Under the influence of an electrolyte, usually water, a very small current will be created between two different metals. As a result of that current, the least noble metal, as it were, will dissolve in the electrolyte and therefore corrodes. On the other hand, the most noble metal will corrode less quickly than normal.
A good example of this is the old schoolboy prank of throwing nails into zinc guttering. Because zinc is a less noble metal than the iron nails, the zinc underneath the nails quickly corrodes, leaving holes in the guttering. But zinc, in turn, can also have a protective effect on another metal. For instance, zinc blocks (anodes) are attached to the hull of steel boats in fresh water. The zinc “sacrifices itself” as a result of which the hull does not start to rust as quickly. In the case of seagoing vessels, aluminium is used instead.
In 2010, galvanic corrosion turned out to be the biggest adversary of a brand new American warship. The seawater created contact between the aluminium hull and the stainless steel propellers as a result of which the hull was attacked so severely by corrosion that within just a year of being launched, the ship had to go back into dock for repairs. The cost: several million dollars.
Therefore combining two different metals in the same structure can have serious consequences for the strength of that structure. Sometimes it is not possible to avoid using two metals together. If that is the case, then measures will have to be taken in order to prevent corrosion by insulating the various metal parts, for example.
We have more than 70 years of experience in corrosion protection. We apply that knowledge for the benefit of drinking water companies, heating companies and infrastructure construction companies. We are aware of the potential problems and can offer sustainable solutions for providing reliable protection for structures against corrosion.
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