Corrosion

Corrosion

Corrosion mainly related to metals and alloys is the deterioration of the metal or alloy as a result of chemical reactions between the metal or alloy and the surrounding environment. The environment could be the atmosphere humidity, seawater, gasses, acids, bases, and salts.


Rust, which is the most popular type of corrosion, is the product of Iron or Iron alloys chemical reaction with air humidity. Quite the same is the green patina found on Copper.

Some metals like Gold, Silver, Platinum, Palladium are called Noble Metals as they almost not corrode and find in nature in pure form.


Some of the corrosion types are: 


  1. General Attack Corrosion: This very common form of corrosion attacks the entire surface of a metal structure. Chemical or electrochemical reactions cause it. 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.
  2. Localized Corrosion: This corrosion attacks only portions of a metal structure. There are three types of localized corrosion:
    1. Pitting -- the creation of small holes in the surface of a metal.
    2. Crevice corrosion – corrosion occurred in stagnant locations such as found under gaskets.
    3. Filiform corrosion – corrosion is occurred when water gets under a coating such as paint.
  3. Galvanic Corrosion: This can occur when two different metals are located together in a liquid electrolyte such as seawater, acting as a galvanic cell. 
  4. Environmental Cracking: When environmental conditions are stressful enough, some metal can begin to crack, fatigue, or become brittle and weakened. 

Corrosion Prevention

From cracks up to total destruction of metal, structures are the corrosion damages. The World Corrosion Organization estimates the global cost of corrosion to be about US$ 2.5 trillion annually, and that a large portion of this - as much as 25% - could be eliminated by applying simple, well-understood prevention techniques. Such techniques are:


  1. Suitable coatings. 
  2. Special corrosion resistance alloys such as Nickel alloys (Hastelloy, Inconel, Inconel, Phynox, Monel, and others) were developed and now in vast use in the form of wires, bars, sheets, etc.… Such alloys could be offered by Medini Ltd. from the high-quality manufacturer Alloy Wire International. 


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