Workshop on Low Corrosion Rates

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Workshop on Low Corrosion Rates

• ASTM Committee G-1
• May 18, 2005, Reno, NV

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Workshop Chairs

• Sheldon W. Dean
• Neal S. Berke
• Sean Brossia

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Traditional Concepts

• Negligible corrosion rate lt1 mpy
• Primary concern loss of strength
• Service Life lt10 to 50 years
• Low corrosion rate problems occur when these
  concepts do not apply

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Low Corrosion Rate Cases

• Nuclear waste storage 100K years
• Medical implants reaction to c.p.s
• Semiconductor manufacturing c.p.s
• Sterile water rouging

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Workshop Objectives

• Examine actual examples of LCRs
• Learn state of art
• Can standards development assist in coping with
  LCR problems?

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Standards Development ASTM G-1 Scope

• Promotion of knowledge
• Stimulation of research
• Collection of engineering data
• Development of standards
• Corrosion
• Methods for corrosion protection

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Types of G-1 Stds.

• Test methods
• Practices
• Guides
• Classifications
• Specifications
• Terminology

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Workshop Program

• Introduction S.W.Dean
• Lab Corrosion Testing of Medical Implants- R.
  Corbett
• Rouging- a Discoloration of Stainless Steel- R.
  Corbett
• Rouging Issues Facing the Pharmaceutical
  Biotech Industries- P. Banes

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Rouging -Terminology

• Terminology G01.02 Meeting
• Development of colored, usually red or brown,
  layer on stainless steel in pure or sterile water
• Not usually associated with localized corrosion
• Not well understood

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Rouging - Conditions

• Major concern for water for injection, WFI
• Also seen in other sterile water systems
• Water usually gt60C
• Water is air saturated
• Low impurity levels, 10 100 ppm Cl
• Long residence times, days or weeks

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Rouging Concerns

• Cosmetic Systems look dirty, unacceptable for
  medical purposes
• Contamination of product with corrosion products
• Future regulation from FDA?

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Rouging Mechanisms

• Deposition of film from colloidal solution
• Precipitation of film from supersaturated
  solution
• Growth of passive film

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Colloidal Deposition

• Passive film dissolves in water releasing ferric
  ions
• Ferric ions precipitate in solution to form
  colloidal particles
• Particles adhere to stainless steel surface
• Mechanism requires particles to be less soluble
  than passive film

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Precipitation

• Passive film dissolves releasing ferric ions
• Ferric ions precipitate on stainless surface
• Film forms and grows
• Problem How can passive film dissolve and
  precipitate at the same time?

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Passive Film Dissolution

• Passive film is amorphous, contains OH
• Fe(OH)3 is much more soluble than ferric oxides
• Fe3 from Fe(OH)3 can precipitate FeOOH or Fe2O3

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Growth of Passive film

• Normal passive film very thin 10 100nm
• Oxidizing conditions cause passive film to
  thicken at a decreasing rate
• When film exceeds 200 nm it becomes visible

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Important Questions

• Potential of stainless steel during rouging?
• Nature of rouge, crystalline or amorphous? Type
  of crystal?
• Particle size and degree of organization of
  rouge?
• Chemical composition of rouge?

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MTI Program

• Purpose to gain fundamental understanding of
  mechanism
• Project development team formed
• Champion M. Renner, Bayer
• Staff F. G. Hodge
• Pourbaix (Potential- pH) diagrams calculated

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Thank You!