Problem 11.3: For each case identify the primary pillar and

From Chapter 11 Problem Set. Level 1: Conceptual Mastery.

Question

For each case, identify the primary pillar and the most likely amplifier:

• Deep pitting beneath brown tubercles on mild steel
• White mineral deposit on a warm tube with soft slime beneath it
• Rapid oxidant demand increase after weeks of poor filtration
• Stable bulk chemistry but increasing condenser approach temperature

Answer

Show answer

These cases allow for some interpretation, but strong answers will generally follow this logic:

• Primary: corrosion. Amplifier: solids/deposit formation. The deposit creates the oxygen differential and helps localize attack.
• Primary: scale. Amplifier: biology. The mineral deposit is the dominant feature, but biofilm likely contributed by insulating the surface and trapping ions.
• Primary: biology. Amplifier: solids. Poor solids control creates shelter and surface area for biological growth, increasing oxidant demand.
• Primary: scale or solids. Amplifier: biology, if biofilm is part of the insulating layer. The key insight is that the problem is likely at the surface rather than in the bulk water.