The Corrosion of Titanium and its Alloys at High Temperatures and Pressures

1
The Corrosion of Titanium and its Alloys at High
Temperatures and Pressures

• James Vaughan
• Peter Reid
• Akram Alfantazi
• David Dreisinger Desmond Tromans
• Mimoune Elboudjaini

2
Outline

• Introduction
• Results
• Conclusions

Introduction
3
Titanium Information

• Abundant on Earth
• Very reactive
• Alloyed for mechanical properties
• (Mo, Ni, Al, V)
• Alloyed for corrosion resistance
• (Pd, Ru, Mo, Ni)

Introduction
4
Motivation

• Ti and Ti-alloys are used as the liner and
  internal components of autoclaves
• Corrosion repairs
• require expensive
• process downtime
• Knowledge of corrosion at these conditions is
  limited

Introduction
5
HPAL Conditions
Introduction
6
Materials Tested
Introduction
7
Objectives

• Explore the electrochemical behaviour of
  Titanium and its alloys at high temperatures and
  pressures in H2SO4
• Characterize the corrosion products

Introduction
8
Approach

• Develop E-pH stability diagrams
• Polarization techniques
• XPS and AES

Introduction
9
Results

• E-pH Stability Diagrams
• 298, 498 Kelvin
• Ti ion activity 1X10-6
• Potential vs. SHE (298 Kelvin)

Results
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E-pH Diagram, 298 Kelvin
Results
11
E-pH Diagram, 498 Kelvin
Results
12
Results
Electrochemical Tests (lt 373 K) SR 0.5 mV /
s Reference Hg / Hg2SO4 Corrected for LJP
Results
13
Open Circuit Potential Ti-1, 100 gpL H2SO4, 298
Kelvin
Results
14
Potentiodynamic Scan Ti-1, 100 gpL H2SO4, 298
Kelvin
Results
15
Anodic Scans Ti-1
Results
16
Results
Electrochemical Tests (gt 423 K) CANMET MTL 30
gpL H2SO4 463, 498 and 523 K
Results
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Open Circuit Potential, High Temperature During
the autoclave warm-up
Results
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E-pH Diagram, 498 Kelvin
Results
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Potentiodynamic Scan, Ti-7, High Temperature
Results
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Potentiodynamic Scan, Ti-12, High Temperature
Results
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Potentiodynamic Scan, Ti-18, High Temperature
Results
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Oxide Film Characterization
XPS and AES Immersion Sample Conditions 30 gpL
H2SO4 498 K 3 Hours
Results
23
XPS Chemical Analysis, Ti-12
Results
24
AES Chemical Depth-Profile, Ti-12
Scan Rate 300 A/min
Titanium
Oxygen
Carbon
Results
25
AES Chemical Depth-Profile, Ti-18
Scan Rate 300 A/min
Titanium
Oxygen
Carbon
Results
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Conclusions

• There was no rapid general corrosion or
  localized corrosion of the samples at the
  conditions tested

Increased stability of the oxide with temperature
Inhibitor ions from the autoclave walls
Conclusions
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Conclusions

• The alloyed samples exhibited a higher open
  circuit potential than the unalloyed samples
• The oxide thickness of the Ti-12 immersion test
  sample was greater than for the Ti-18

Conclusions
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Acknowledgements

• CANMET Materials Technology Laboratories
• TIMET (Titanium Metals Corporation)
• NSERC

Conclusions