Corrosion Forms

Once you have finished reading this material you can check your skills with a self test.

Recommendations for sound corrosion control into components and systems require that a special care is given to the forms or types of corrosion that can occur. However, one has to realize that one type of corrosion can lead into a series of worsening reactions where other types of corrosion attack can become the dominating factors. A simple galvanic situation aggravated by the presence of an electrolyte can cause devastating effects as was observed in the supporting saddles of the Statue of Liberty during its restoration. The different forms of corrosion represent corrosion phenomena categorized according to their appearance: 

• Group 1 - readily identifiable by ordinary visual examination

  • Uniform corrosion

  • Pitting

  • Crevice corrosion

    • crevice model

    • pack rust

  • Galvanic corrosion

  • Lamellar corrosion

• Group 2 - may require supplementary means of examination

  • Erosion corrosion

  • Cavitation

  • Fretting corrosion

  • Intergranular corrosion

  • Exfoliation

  • Dealloying (selective leaching)

• Group 3 - verification is usually required by microscopy (optical, electron microscopy etc.)

  • Environmental cracking

    • Stress Corrosion Cracking (SCC)

    • Corrosion fatigue

    • Hydrogen embrittlement