Recognizing Corrosion

Module Six of CCE 281 Corrosion: Impact, Principles, and Practical Solutions

Lesson Objectives

• Examine ways to recognize a corrosion problem

• Describe the various forms of corrosion attack

• Discuss the consequences of hidden corrosion

• Compare the mechanisms that can initiate and propagate a corrosion process

Introduction

The previous Modules have introduced the general science of corrosion processes. In reality, the principles that govern these scientific concepts are rarely of interest to most people facing corrosion problems. The main questions these people generally ask are:

• How serious is the problem?

• How can it be fixed and how much will it cost?

• What caused the problem in the first place?

The present Module will focus on answering the first of these questions and the next Module the last. Corrosion damage can take many shapes and forms that are often related to specific alloy/environment/operation conditions. The several forms of corrosion may be divided into three groups [1]:

1. Those recognizable with the unaided eye

2. Those which are more easily discerned with specific aids (e.g. dye penetrants, magnetic particles, or low-power microscopy)

3. Those which can only be identified definitely by optical or electronic microscopy

Main forms of corrosion attack regrouped by their ease of recognition

Much can be deduced from examination of materials which have failed in service. It is often possible by visual examination to decide which corrosion mechanisms have been at work and what corrective measures are required to solve the problem

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Information Module

• Introduction

• General or Uniform Attack

• Localized Corrosion

  • Pitting corrosion

  • Crevice corrosion

  • Galvanic corrosion

    • galvanic series

    • area effects

    • deposition corrosion

  • Intergranular corrosion

  • Dealloying

  • Hydrogen induced cracking (HIC)

  • Hydrogen embrittlement (HE)

• Velocity Induced Corrosion

  • Erosion-corrosion

  • Cavitation

  • Impingement

• Mechanically Assisted Corrosion

  • Stress corrosion cracking

  • Corrosion fatigue

  • Fretting corrosion

See also CCE 513: Corrosion Engineering

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