Corrosion types and its prevention

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Corrosion types and its prevention
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What is corrosion?

• Corrosion is the deterioration of a metal as a
  result of chemical reactions between it and the
  surrounding environment. Both the type of metal
  and the environmental conditions,
  particularly gasses that are in contact with the
  metal, determine the form and rate of
  deterioration.

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Do All Metals Corrode?

• All metals can corrode. Some, like pure iron,
  corrode quickly. Stainless steel, however, which
  combines iron and other alloys, is slower to
  corrode and is therefore used more frequently.
• All small group of metals, called the Noble
  Metals, are much less reactive than others. As a
  result, they corrode rarely. They are, in fact,
  the only metals that can be found in nature in
  their pure form. The Noble Metals, not
  surprisingly, are often very valuable. They
  include copper, palladium, silver, platinum, and
  gold.

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Types of Corrosion

• There are many different reasons for metal
  corrosion. Some can be avoided by adding alloys
  to a pure metal. Others can be prevented by
  a careful combination of metals or management of
  the metal's environment. Some of the most common
  types of corrosion are described below.
• General Attack Corrosion
• Localized Corrosion
• Galvanic Corrosion
•  Environmental Cracking

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• General Attack Corrosion
• This very common form of corrosion attacks the
  entire surface of a metal structure. It is caused
  by chemical or electrochemical reactions. While
  general attack corrosion can cause a metal to
  fail, it is also a known and predictable issue.
  As a result, it is possible to plan for and
  manage general attack corrosion.
•  Localized Corrosion
• Localized corrosion attacks only portions of a
  metal structure. There are three types of
  localized corrosion
• Pitting -- the creation of small holes in the
  surface of a metal.
• Crevice corrosion -- corrosion that occurs in
  stagnant locations such as those found under
  gaskets.
• Filiform corrosion corrosion that occurs when
  water gets under a coating such as paint.
  weakness.

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• Galvanic Corrosion
• Galvanic corrosion can occur when two different
  metals are located together in a liquid
  electrolyte such as salt water. In essence, one
  metal's molecules are drawn toward the other
  metal, leading to corrosion in only one of the
  two metals.
• Environmental Cracking
• When environmental conditions are stressful
  enough, some metal can begin to crack, fatigue,
  or become brittle and weakened. 

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corrosion prevention systems

• In virtually all situations, metal corrosion can
  be managed, slowed, or even stopped by using the
  proper techniques.
• Corrosion prevention can take a number of forms
  depending on the circumstances of the metal being
  corroded.
• Corrosion prevention techniques can be generally
  classified into 6 groups
• Environmental Modifications
• Metal Selection and Surface Conditions
• Cathodic Protection
• Corrosion Inhibitors
• Coating
• Plating