Corrosion Data Trends, Identification, and Verification
What the exam expects
You must read corrosion data as a trend, not a snapshot. Key concepts:
- Data types: inspection (UT, MFL, visual), monitoring (coupons, ER/LPR probes, sampling), and process data (flow, pressure, temperature).
- Trend analysis: compare rates over time; distinguish stable, accelerating, and step-change behavior.
- Verification: confirm a suspected trend with an independent method before acting.
- Data quality: calibration, probe fouling, coupon placement, and representativeness.
Traps in questions
- Acting on a single reading without confirming the trend.
- Confusing corrosion rate with remaining life; rate alone does not give life without wall thickness and design margin.
- Ignoring probe placement; a probe in a stagnant zone does not represent the flowing line.
- Treating ER probe response as chemistry-specific; ER measures metal loss, not mechanism.
Worked example
An ER probe shows a rate spike after a water-cut increase. The correct response is to verify with a coupon or UT and check process data before declaring a corrosion event, then adjust monitoring frequency. Rule of thumb: a trend needs at least two consistent data points plus a process explanation; a single point is a question, not a conclusion.