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 - PowerPoint PPT PresentationTRANSCRIPT
CORROSION
Introduction
Forms of Corrosion o Uniform Corrosion o Pitting Corrosion o Stress Corrosion Crackingo Crevice Corrosiono Erosion Corrosiono Intergranular Corrosiono Hydrogen Damage
o Corrosion Fatigueo Concentration Cell Corrosion
o Fretting Corrosion o Dealloying o Corrosion in Concrete
CONTENTS
Electrochemical cell
The components in an 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.
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
Car Corrosion
Examples
Corrosion of Implants
Portion Of Different Forms Of Corrosion
Uniform Corrosion
Pitting Corrosion
Potential (Volts)
Current Density
A/cmicrit2
a - activation control
Epp
Passive region
Transpassive region
101
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.
Stress Corrosion Cracking
Because grain boundaries have a high energy, they are anodic and corrode.
River Branching Pattern
Intergranular SCC Of An Aluminum Aerospace Part
The arrows indicate the primary crack shown in both pictures
Changes in alloy heat treatment recommended
Corrosion occurs at the tip of a crevice because of limited access to oxygen.
Crevice Corrosion
Erosion Corrosion
In austenitic stainless steel, precipitation of chromium carbide makes the low Cr austenite in the grain boundaries anodic.
Intergranular Corrosion
Exfoliation Corrosion
Example of microgalvanic cells in two-phase alloys :
In steel, ferrite is anodic to cementite
Galvanic Corrosion
Hydrogen Damage
Hydrogen Embrittlement of Valve Capscrew Fasteners
Corrosion Fatigue
Corrosion fatigue cracks on the I.D. of a Admiralty brass exchanger tube
Corrosion Fatigue Cracks In AISI 1020 Steel In Oil And Gas
Downhole Service
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 :
1. http://corrosion.ksc.nasa.gov
2. http://www.corrosion-doctors.org
3. http://www.hghouston.com
4. The Science and Engineering of Materials, 4th ed Donald R. Askeland
– Pradeep P. Phuile’