Steel Bridge Corrosion Issues

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Steel Bridge Corrosion Issues

• Presenter
• Anthony Peterson

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Steel Bridge Corrosion Issues

• Outline
• Background
• Chemistry
• Corrosion Situations
• Maintenance Strategies
• Corrective Measures
• Current Practice
• Predictive Modeling
• Conclusions
• Questions

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Steel Bridge Corrosion Issues

• Background
• Relatively New
• CSA S16
• Desired for
• Consistency
• Aesthetics
• Customizability
• Constructability
• Variety of Design
• Main Detractions
• Corrosion
• Cost

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Steel Bridge Corrosion Issues

• Background
• Corrosion Issues
• Cost to United States Infrastructure US276
  Billion, 3.1 GDP (1998)
• Limited Education
• Limited Undergraduate
• Graduate Specific
• Limited Industrial Guidance
• Decision Making Problems
• Government Policy
• Funding

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Steel Bridge Corrosion Issues

• Chemistry
• Unique Redox Cell
• Base Steel is Anode Cathode
• Anode
• Location of Steel releasing e-
• Apparent Loss of Steel
• Cathode
• Location of Steel accepting e-
• Apparent Rust
• Oxygen
• Electrolyte -- Cl- and other salts

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Steel Bridge Corrosion Issues

• Corrosion Situations
• 1 Atmospheric Zone
• Moderate Corrosion
• Low-High Cl- High O2 Low Moisture
• De-icing Salts
• 2 Splash Zone
• Severe Corrosion
• Highest Cl- High O2 Frequent Wet/Dry
• 3 Tidal Zone
• High Corrosion
• High Cl- High O2 Periodic Wet/Dry
• 4 Submerged Zone
• Low Corrosion
• Variable Cl- Low O2
• 5 Mudline Zone
• Low Corrosion
• Variable Cl- Low O2

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Steel Bridge Corrosion Issues

• Corrosion Situations
• General
• Uniform Easily seen
• Expected
• Usually slow process
• Localized
• Particular Can be difficult to see
• Attempt to avoid
• Variability in speed
• Types
• Crevice
• Pitting
• Granular
• Other

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Steel Bridge Corrosion Issues

• Corrosion Situations
• Type Crevice Corrosion
• Microclimate
• Lack of Oxygen initiates Cathode/Anode split
• Uneven Attack
• Initiation Theories
• 1 Critical Crevice Solution (CCS)
• Generation of Chemical species in Crevice
• Transportation out of Crevice
• 2 Critical IR Drop Model (IR)
• Geometry and Conductivity
• Current generation and Crevice resistance

Rusting
Cathode
Anode
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Steel Bridge Corrosion Issues

• Maintenance Strategies
• Predictive
• Planned Mitigation
• Preventative
• Inspection and Maintenance
• Corrective
• Wait until Corrosion Presents
• Patch-work type scheme

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Steel Bridge Corrosion Issues

• Corrective Measures
• Paint Coating
• Inhibitive, Sacrificial, Barrier
• Touch-Up Painting
• Simple
• Little Preparation
• Not too Disruptive
• Routine Inspection
• Moderate Longevity
• Overcoat Painting
• Large Undertaking
• Preparation
• Disruptive
• Cost-Benefit Analysis Important
• Long Longevity

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Steel Bridge Corrosion Issues

• Corrective Measures
• Recoat Painting
• Large Undertaking
• The Most Preparation
• Disruptive
• Cost-Benefit Analysis Important
• Greatest Longevity
• Do-Nothing Approach
• Social and Economic Issues
• Cost-Benefit Analysis Very Important

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Steel Bridge Corrosion Issues

• Corrective Measures
• Hot-Dip Galvanization
• CSA G164
• Two Defensive Actions
• (1) Barrier
• (2) Anodic
• Expensive
• Size Limitations
• In-Field Remediation Issues
• Cold Galvanization
• In-Field
• Small Scale, low preparation
• Brush, Roller, Spray applications
• -Electroplating- (Small Scale)
• Other
• Mechanical Coating Sheridizing Zinc flakes or
  dust, etc.

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Steel Bridge Corrosion Issues

• Corrective Measures
• Weathering Steel
• Beneficial, Stable Rust
• Conditional Implementation
• No prolonged wetting
• Wet/Dry cycle necessary
• Limited concentrations of corrosive pollutants
  de-icing salts
• Detailing preventing trapped debris and moisture
• CSA S16.01
• Types R, A, AT
• Subject to availability
• Designed into Bridge
• Difficult as method of remediation

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Steel Bridge Corrosion Issues

• Corrective Measures
• Thermal Spray
• Molten Metal Spray, Metallizing CSA G189
• Zinc or Aluminum
• Powder coating, substrate heating
• Impressed Current
• Electrical Circuit
• Source of electrons
• Sacrificial Anode
• Galvanization is a form
• Zinc or other metal pieces
• Uncommon for Bridges

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Steel Bridge Corrosion Issues

• Corrective Measures
• Design
• Conceptual Design
• Materials
• Type of Bridge
• Type of Use
• Time Frame
• Users
• Other
• Detailing
• Drainage
• Component Interaction
• Maintenance

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Steel Bridge Corrosion Issues

• Corrective Measures
• Inspection
• Types
• Visual
• Electronic
• Ultrasonic
• Thermographic
• Radiographic
• Other
• Schedule
• Training
• Cost / Time

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Steel Bridge Corrosion Issues

• Current Practice
• BC Ministry of Transportation
• 1 Inspection
• Condition Inspection Report
• Ratings of Bridge, and its components
• 2 Decision Maker (Area Manager)
• Scope and Prioritization
• Classification (Large, Small, Do-Nothing)
• 3 Maintenance
• Large Ministry Involvement (Region Highways)
• Small Ministry Maintenance Contractors
• Do-Nothing

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Steel Bridge Corrosion Issues

• Predictive Modeling
• Decision Making Tool
• Varying Complexity
• Deterministic
• Probabilistic
• Varying Accuracy
• Maintenance Assumptions
• Individual Bridge Concerns
• One Rating
• Component Ratings
• Groupings of Bridges
• Regional Strategies
• Allocation of Resources

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Steel Bridge Corrosion Issues

• Predictive Modeling
• Methodology
• User-Friendly
• Time Value of Money
• Painting/Coating Focus
• Additional Input Option
• Software
• DecisionPro
• Microsoft Excel
• Usage
• Developed for BC Ministry of Transportation
• Easily Adaptable

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Steel Bridge Corrosion Issues

• Predictive Modeling
• Deterministic
• One Steel Bridge
• Inspection ASTM D610 Rating
• 8 - 10 Minor Damage
• 5 - 7 Fair Damage
• 0 - 4 Severe Damage
• Annual Funding Estimation

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Steel Bridge Corrosion Issues

• Predictive Modeling
• Input
• ASTM Corrosion Rating
• Corrosion Degradation Relation
• Escalation Rate (Inflation)
• Interest (TVM)
• Bridge Surface Area
• Touch-Up, Overcoat and Recoat Durability and Unit
  Costs
• Replacement Cost
• Additional Costs
• Output
• Preferred Strategy
• Predicted Equivalent Uniform Annual Cost (TVM)

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Steel Bridge Corrosion Issues

• Predictive Modeling
• Deterministic
• Grouping of Steel Bridges
• Inspection ASTM D610 Rating
• 8 - 10 Minor Damage
• 5 - 7 Fair Damage
• 0 - 4 Severe Damage
• Additional Input
• Number of Bridges
• Additional Output
• Group Funding
• Cost-Benefit Analysis of Each Bridge
• Priority ranking of each Bridge
• Estimated Annual Funding of Overall Maintenance

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Steel Bridge Corrosion Issues

• Conclusions
• Many Uncertainties
• Type of Corrosion
• Location of Corrosion
• Type of Mitigation
• Decision Making
• Education
• Current Policy
• Systematic Model

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Questions?

• Thank You