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The methods not used to prevent corrosion of metals is:
1. Coating with bisphenol
2. Barrier protection
3. Coating with phenol
4. Alloying with suitable metal (S)

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Correct Answer - Option 3 : Coating with phenol

Concept -

Corrosion:

  • Corrosion is the oxidation-induced deterioration of certain materials, both metals, and non-metals.
  • When a substance is exposed to air or certain chemicals, it can corrode.
  • It can occur on different surfaces of substances like wood, alloys, metal, etc. 
  • Degradation is a type of corrosion that can occur in materials such as polymers and ceramics.
  • Corrosion reduces the durability of these substances. 

Methods to Prevent Corrosion: 

1. Coating with bisphenol -

  • Steel is prevented from corrosion with the help of a coating of epoxy or polyurethane. 
  • These two substances used to prevent corrosion contain bisphenol-A
  • These coatings act as anti-corrosion material.
  • Recent researches have intrigued the use of these materials because of harmful environmental factors. 

2. Barrier protection -

  • Barrier coatings such as paint, plastic, or powder are one of the simplest and cheapest ways to prevent corrosion.
  • To generate a thin coating, powders such as nylon, and urethane are heated to the metal surface.
  • Metal surfaces are frequently treated with plastic and waxes.
  • Paint is a covering that protects metal surfaces against electrochemical charges caused by corrosive substances.

​3. Galvanization -

  • The process of putting a protective zinc coating to iron to prevent rusting is known as galvanization.
  • It extends the life of iron parts by establishing a membrane between the metal and the air, which prevents iron oxide from developing on the steel layer.
  • Galvanization also provides greater corrosion protection to parts that are exposed to air.
  • Galvanizing protects against rust and corrosion in several ways:
  1. It acts as a barrier, preventing corrosive chemicals from reaching the iron beneath.
  2. The zinc acts as a sacrificial anode, meaning that even if the coating is damaged, the exposed steel is still protected by the zinc that remains on it.
  3. The zinc surface reacts with the environment to generate a dense, adhering patina that is impervious to moisture.

4. Alloying -

  • Combining the qualities of multiple metals to provide increased strength and resistance to the finished product creates a material that resists corrosion.
  • For example steel, an alloy is one of the most efficient corrosion protection solutions available.
  • Combining corrosion-resistant nickel with oxidation-resistant chromium and carbon makes a material that is corrosion resistant and provides better durability. ​

Explanation:

  • Corrosion is the deterioration of certain materials which makes their durability affected. 
  • Different methods are used to prevent corrosion.
    • Galvanization
    • Coating with bisphenol 
    • Barrier protection. 

All these methods are used except the one in the given potions in the question - coating with phenol.

So, the correct answer to this question is - Coating with phenol. 

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