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Workshop on Low Corrosion Rates

Workshop on Low Corrosion Rates. ASTM Committee G-1 May 18, 2005, Reno, NV. Workshop Chairs. Sheldon W. Dean Neal S. Berke Sean Brossia. Traditional Concepts. Negligible corrosion rate: <1 mpy Primary concern: loss of strength Service Life: <10 to 50 years

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Workshop on Low Corrosion Rates

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  1. Workshop on Low Corrosion Rates ASTM Committee G-1 May 18, 2005, Reno, NV

  2. Workshop Chairs • Sheldon W. Dean • Neal S. Berke • Sean Brossia

  3. Traditional Concepts • Negligible corrosion rate: <1 mpy • Primary concern: loss of strength • Service Life: <10 to 50 years • Low corrosion rate problems occur when these concepts do not apply

  4. Low Corrosion Rate Cases • Nuclear waste storage: 100K years • Medical implants: reaction to c.p.’s • Semiconductor manufacturing: c.p.’s • Sterile water: rouging

  5. Workshop Objectives • Examine actual examples of LCR’s • Learn state of art • Can standards development assist in coping with LCR problems?

  6. Standards Development: ASTM G-1 Scope • Promotion of knowledge • Stimulation of research • Collection of engineering data • Development of standards: • Corrosion • Methods for corrosion protection

  7. Types of G-1 Stds. • Test methods • Practices • Guides • Classifications • Specifications • Terminology

  8. 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

  9. 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

  10. Rouging - Conditions • Major concern for water for injection, WFI • Also seen in other sterile water systems • Water usually >60°C • Water is air saturated • Low impurity levels, 10 –100 ppm Cl • Long residence times, days or weeks

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

  12. Rouging Mechanisms • Deposition of film from colloidal solution • Precipitation of film from supersaturated solution • Growth of passive film

  13. 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

  14. 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?

  15. Passive Film Dissolution • Passive film is amorphous, contains OH – • Fe(OH)3 is much more soluble than ferric oxides • Fe+3 from Fe(OH)3 can precipitate FeOOH or Fe2O3

  16. 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

  17. 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?

  18. 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

  19. Thank You!

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