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CORROSION

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CORROSION - PowerPoint PPT Presentation


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CORROSION. CONTENTS. Introduction Forms of Corrosion Uniform Corrosion Pitting Corrosion Stress Corrosion Cracking Crevice Corrosion Erosion Corrosion Intergranular Corrosion Hydrogen Damage Corrosion Fatigue

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Presentation Transcript
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CONTENTS

  • Introduction
  • Forms of Corrosion
    • Uniform Corrosion
    • Pitting Corrosion
    • Stress Corrosion Cracking
    • Crevice Corrosion
    • Erosion Corrosion
    • Intergranular Corrosion
    • Hydrogen Damage
    • Corrosion Fatigue
    • Concentration Cell Corrosion
    • Fretting Corrosion
    • Dealloying
    • Corrosion in Concrete
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Electrochemical cell

A cell in which electrons and ions can flow by separate paths between two materials, producing a current which, in turn, leads to corrosion or plating.

The components in an electrochemical cell

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Electrochemical corrosion

Corrosion produced by the development of a current in an electrochemical cell that removes ions from the material.

CORROSION:

Degradation of metals and is often called RUST

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Examples

Car Corrosion

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Stress Corrosion Cracking

Examples of stress cells

Cold work required to bend a steel bar introduces high residual stresses at the bend, which then is anodic and corrodes.

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The arrows indicate the primary crack shown in both pictures

Intergranular SCC Of An Aluminum Aerospace Part

Changes in alloy heat treatment recommended

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Crevice Corrosion

Corrosion occurs at the tip of a crevice because of limited access to oxygen.

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Intergranular Corrosion

In austenitic stainless steel, precipitation of chromium carbide makes the low Cr austenite in the grain boundaries anodic.

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Galvanic Corrosion

Example of microgalvanic cells in two-phase alloys :

In steel, ferrite is anodic to cementite

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Hydrogen Damage

Hydrogen Embrittlement of Valve Capscrew Fasteners

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Corrosion Fatigue Cracks In AISI 1020 Steel In Oil And Gas Downhole Service

Corrosion fatigue cracks on the I.D. of a Admiralty brass exchanger tube

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Concentration Cell Corrosion

Corrosion occurs beneath a water droplet on a steel plate due to low oxygen concentration in the water.

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References :

  • http://corrosion.ksc.nasa.gov
  • http://www.corrosion-doctors.org
  • http://www.hghouston.com
  • The Science and Engineering of Materials, 4th ed Donald R. Askeland – Pradeep P. Phuile’
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