What is Corrosion?
Corrosion is the defined as both to the degradation reaction of metal and alloy, the destruction caused by this reaction. Corrosion is an event that occurs as a result of the reaction of metallic materials with the environment they are in, without the need for external energy.
The corrosion that occurs on the surface of metallic materials in environments containing water is called “aqueous corrosion”. Corrosion occurred on metals in the atmosphere, underground, reinforced concrete or any kind of aqueous chemical is an example of this. Corrosion that occurs as a result of chemical reaction of gases and metals at high temperatures where water is not stable is “dry” or “high temperature corrosion”. Corrosion in the parts of boilers that come into contact with flame or hot gases is an example. In addition to these two very important types of corrosion, corrosion caused by “organic liquids” or “molten metals” can also be mentioned.
Principles of Corrosion Protection
Corrosion is a “surface” phenomenon that occurs at the metal-environment interface as a result of contact of metals with the environment. Degradation reaction occurred in areas of metals that are not in contact with the environment can not be called as corrosion. Besides, in the event of corrosion, the material must undergo an “electrochemical” change. Deterioration caused by mechanical reasons (such as abrasion, breakage) is not corrosion.
As briefly summarized, corrosion occurs with the interaction of the “Metal-Interface-Environment” trio. Knowing the characteristics of these three elements and their relations with each other and making the necessary changes lie on the basis of corrosion protection measures.
Corrosion protection measures should be of “preventing”, “reducing” or “controlling” features. For this reason, “corrective” measures as well as “preventive” measures should be considered at the design stage and made as a part of corrosion protection.
Consequently, corrosion protection methods can be listed as:
A – Design
B - Precautions related to metal and alloy
C - Precautions related to environment
D - Precautions related to Interfaces.