Comprehensive and Detailed Explanation From Exact Extract:
Grooving corrosion in cooling water systems is a well-documented damage mechanism in API RP 571, particularly associated with high-velocity flow conditions.
Flow-induced erosion (also referred to as erosion-corrosion or flow-assisted corrosion) occurs when:
High fluid velocity removes protective corrosion films
Local turbulence, elbows, or inlet zones focus mechanical wear
Soft metals or alloys are exposed to continuous impingement
This results in smooth, directional grooves or channels aligned with the flow direction, a classic signature described in API RP 571.
Why the other options are incorrect:
Option A: ERW defects affect weld seams, not general grooving patterns.
Option B: MIC typically causes localized pitting, not uniform grooving.
Option D: Underdeposit corrosion produces irregular pitting beneath deposits, not flow-aligned grooves.
API RP 571 specifically identifies flow-induced erosion as a primary cause of grooving in cooling water heat exchanger tubes.
Referenced Documents (Study Basis):
API RP 571 – Section on Erosion/Erosion-Corrosion
API Cooling Water System Corrosion Study Guide
======================
