Corrosion

• What is the definition of corrosion?


  Corrosion is the destruction of materials by chemical reactions with substances in the environment.
• What is a common example of corrosion?


  Rusting is a common example of corrosion.
• To which metals does the term "rusting" apply?


  Rusting only applies to iron and alloys of iron such as steel.
• What should you use to describe the corrosion of metals other than iron?


  You should use the word "corroding" for metals other than iron.
• What are the conditions required for rusting based on the experiment with test tubes?

  • Test tube 1: Iron nail in distilled water and air (rust forms)
  • Test tube 2: Iron nail in boiled distilled water (no air, no rust)
  • Test tube 3: Anhydrous calcium chloride (no water, no rust)
  • Conclusion: Rusting requires both air and water
• What prevents corrosion when using a barrier method?


  A barrier prevents environmental substances from contacting the material.
• What are some methods to prevent corrosion?


  • Use of grease or paint as a barrier
  • Coating with a metal (electroplating)
  • Formation of a protective oxide layer (e.g., aluminum oxide)
• What is the protective layer formed on aluminum when it reacts with oxygen?


  The protective layer is aluminum oxide.
• What is galvanizing?


  Galvanizing is coating iron with zinc to prevent corrosion.
• How does zinc protect iron when used in galvanizing?


  Zinc acts as a barrier and is more reactive than iron, corroding instead of iron.
• What is sacrificial protection?


  Using a more reactive metal to corrode instead of the metal being protected.
• Why are zinc bars used on the steel hull of a ship?

  Zinc bars corrode instead of the steel hull because zinc is more reactive than iron.