corrosion of steel in concrete docs/understanding the... · 2018. 9. 18. · – -720mv vs silver /...
TRANSCRIPT
![Page 1: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/1.jpg)
Corrosion of Steel in Concrete
Dr Chris Atkins
![Page 2: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/2.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Why?
Why?
![Page 3: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/3.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
How?
• Anodes and Cathodes
• Anode loses Metal
• Cathode reacts with oxygen and water
• Electrons in the metal
• Ions in the Electrolyte
How?
![Page 4: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/4.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
How?
Salt Solution
ZINC
CO
PPERHow?
![Page 5: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/5.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Steel in Concrete
• Passive Film Protects
• But….– Chlorides
– Carbonation
• Steel Rusts– Lose reinforcement
• Rust is bigger than steel
• Bits fall off
Steel in Concrete
![Page 6: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/6.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Steel in Concrete - Carbonation
Steel in Concrete
![Page 7: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/7.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Steel in Concrete - Chlorides
Steel in Concrete
![Page 8: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/8.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Steel in Concrete - Chlorides
CATHODES
ANODES
RepairedCATHODE
SALTY and ANODIC
Steel in Concrete
![Page 9: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/9.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Cathodic Protection
• Using CP stops rust in any environment
• Chloride contaminated concrete can remain
• Saves – Propping
– Access
– Materials
– Carbon
• Impressed Current or Galvanic
Cathodic Protection
![Page 10: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/10.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Cathodic Protection
½O2 + H2O + 2e- (metal) 2OH- (aq.)
Fe (metal) Fe2+ + 2e-
eee
+ve
Cl- Cl- Cl-
WATER WATEROH-
OH-
OH-
OH-
Cathodic Protection
WATER
![Page 11: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/11.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Documents
• BS EN 12696 2000 - CP of concrete– Includes criteria
• BS EN 15257 2006 – Certification of CP people
• BA 83 – Highways Agency Advice Note
• TR 36 & 37 – Concrete Society Guidance (Being revised, numbers to change)
Documents
![Page 12: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/12.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Documents
• BS EN 12696:– -720mV vs Silver / Silver Chloride / 0.5M
Potassium Chloride
• Or– 100mV Decay in 24 hours
• Or– 150mV decay over longer periods
• AND
• No potentials more negative than -900mV for prestressed concrete
Documents
![Page 13: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/13.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Hydrogen Embrittlement
• If steel is >600MPa UTS
• AND– Is under high stress
• AND– Is susceptible to it
• AND – Hydrogen is being generated
• Risk of hydrogen embrittlement
Hydrogen Embrittlement
![Page 14: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/14.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Hydrogen Embrittlement
• Most cases are self corrosion in very high strength steels
• Simple to avoid in most reinforced concrete
• Don’t turn the system up that high
• We rarely achieve the -720mV
• All the systems I have designed, commissioned or monitored have never come close to -900mV
Hydrogen Embrittlement
![Page 15: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/15.jpg)
Why?
How?
Steel in Concrete
Cathodic Protection
Summary
Hydrogen Embrittlement
Documents
Summary
• Steel rusts• For chloride induced corrosion CP saves
– Carbon Dioxide– Repairs– Access– Propping
• Codes are available– Competence of personnel– Safe Operation of Systems
• Any Questions???
£
Summary
![Page 16: Corrosion of Steel in Concrete Docs/Understanding the... · 2018. 9. 18. · – -720mV vs Silver / Silver Chloride / 0.5M Potassium Chloride • Or – 100mV Decay in 24 hours •](https://reader035.vdocuments.site/reader035/viewer/2022081619/60eb425d8b60f63b8b191bca/html5/thumbnails/16.jpg)
www.mottmac.com