Lay-up Protection for Boilers and HRSGs - American Public Power ...

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Oxygen Pitting • Starts with a deposit • Driven by oxygen in the water/air versus no oxygen under the deposit • Heating increases corrosion rate • Chloride increases corrosion rate 10
Normal Passivation Half Reactions Fe → Fe +2 + 2e - 1 / 2 O 2 + H 2 O + 2 e - → 2 OH - Fe +2 + 2 OH - Fe (OH) 2 2 Fe(OH) 2 + O 2 Fe 2 O 3 + H 2 O (300 F) Fe 0 2e - Fe 2 O 3 O 2 OH - Fe +2 Fe(OH) 2 Fe 3 O 4 Anode Steel Cathode 11
Page 1 and 2: Lay-up Protection for Boilers and H
Page 3 and 4: Goals of Proper Lay-up • Minimize
Page 5 and 6: Lay-up is Critical for HRSG’s •
Page 7 and 8: Your Choice Passivation and Protect
Page 9: Oxygen Pitting Causes: • Downtime
Page 13 and 14: Oxygen Pitting Deposits create a lo
Page 15 and 16: Corrosion Fatigue Causes: • Oxyge
Page 17 and 18: Underdeposit Corrosion Causes: •
Page 19 and 20: Lay-up Considerations Quick return
Page 21 and 22: Corrosion Triangle 21
Page 23 and 24: Wet Lay-up — Excludes Oxygen 23
Page 25 and 26: Design Issues Affecting Layup • C
Page 27 and 28: Dry Lay-up Advantages • Only opti
Page 29 and 30: Steps for Dry Lay-up • Drain HRSG
Page 31 and 32: Dehumidified Air • Air must circu
Page 33 and 34: Vapor Phase Inhibitors • Used on
Page 35 and 36: VPI Preservation After 30 days Afte
Page 37 and 38: Wet Lay-up Disadvantages • Requir
Page 39 and 40: Nitrogen Cap Cap should be applied
Page 41 and 42: Nitrogen Addition Points Vent HP Tu
Page 43 and 44: Nitrogen Cap- Drums • Enters the
Page 45 and 46: Wet Chemical Lay-up • pH of water
Page 47 and 48: Wet Chemical Lay-up • Requires si
Page 49 and 50: Transitions Wet to Dry (Cold) • D
Page 51 and 52: Startup Chemistry Dry Lay-up Boiler
Page 53 and 54: Startup Chemistry Wet Lay-up (Nitro

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