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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CORROSION

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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

    • Concentration Cell Corrosion

    • Fretting Corrosion

    • Dealloying

    • Corrosion in Concrete


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


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


Examples

Car Corrosion


Corrosion of Implants


Portion Of Different Forms Of Corrosion


Uniform Corrosion


Pitting Corrosion


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.


Because grain boundaries have a high energy, they are anodic and corrode.


River Branching Pattern


The arrows indicate the primary crack shown in both pictures

Intergranular SCC Of An Aluminum Aerospace Part

Changes in alloy heat treatment recommended


Crevice Corrosion

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


Erosion Corrosion


Intergranular Corrosion

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


  • Exfoliation Corrosion


Galvanic Corrosion

Example of microgalvanic cells in two-phase alloys :

In steel, ferrite is anodic to cementite


Hydrogen Damage

Hydrogen Embrittlement of Valve Capscrew Fasteners


Corrosion Fatigue


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


Concentration Cell Corrosion

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


Fretting Corrosion


Dealloying


Photomicrograph of a copper deposit in brass, showing the effect of dezincification (x50).


Filiform Corrosion


Corrosion in Concrete


THANK YOU FOR YOUR KIND ATTENTION


  • 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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