Corrosion

What is corrosion?

Corrosion is a natural phenomenon and is nothing but a reaction that occurs between oxygen and a metal oxide. The ” official” definition is: corrosion is an undesirable deterioration of a material due to chemical or electrochemical reactions with components from the environment . The corrosion word comes from Latin and means ” digest” . All metals are more or less sensitive to corrosion.

Effects of corrosion.

Corrosion leads to loss of strength of the metal, since the corrosion products (oxides and salts) are much weaker than the metal. The corrosion products crumble and the metal parts become thinner. This process produces pit formations which quickly arise in metal parts . These pit formations can eventually cause holes in the metal. The speed and extent of the corrosion process is very different and dependent on a variety of factors such as: the temperature , the medium, the difference in potential between the different metals and the PH value.

An additional problem is , that the corrosion products occupy a larger volume than the diminution of the metal.

With some types of metal corrosion an impervious layer of metal oxide is formed , so that the corrosion process stops.
If this oxide layer is affected by, e.g., an abrasive operation ( erosion ) due to solid particles in the medium then the corrosion process continues.
Generally speaking, there are a number of main forms of corrosion namely Galvanic Corrosion, Erosion & Cavitation.

Here are some examples of the impact corrosion can have:

Bronze pump casing affected the various natural oxide layer exhibited in different colours, it is clearly visible that a lot of material has been affected and receded.

Afbeelding 371

Bronze pump impeller

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Pipe piece

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Internal part cooler cover blasted, pitting around the surface.

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More information about corrosion found on Wikipedia or corrosie.nl.