NACE Corrosion Monitoring Techniques 3

Question 1

Multielectrode array (MEA) sensors are particularly well suited for detecting which type of corrosion?

Accepted Answer

Localized corrosion such as pitting by measuring non-uniform current distribution between electrodes

Answer

Uniform general corrosion across large pipe sections

Answer

Stress corrosion cracking initiating at weld heat-affected zones

Answer

External corrosion under active cathodic protection

Question 2

In a risk-based corrosion monitoring program, monitoring locations are selected based primarily on:

Accepted Answer

Risk assessment combining probability of corrosion occurrence and consequence of failure

Answer

Ease of access and installation cost alone

Answer

Pipe diameter and wall thickness specifications alone

Answer

Regulatory requirements without site-specific engineering assessment

Question 3

A negative shift in free corrosion potential (Ecorr) during monitoring of a steel structure typically indicates:

Accepted Answer

Increased anodic activity suggesting higher corrosion rate or active corrosion onset

Answer

Improved corrosion resistance due to passive film formation

Answer

Effective cathodic protection current being applied to the structure

Answer

Complete depletion of dissolved oxygen from the electrolyte

Question 4

Radiographic inspection (RT) used as a corrosion assessment tool is best described as:

Accepted Answer

A periodic, non-destructive offline method providing cross-sectional images revealing internal wall loss

Answer

An online continuous monitoring method using real-time X-ray imaging

Answer

A surface contact examination technique requiring grinding or surface preparation

Answer

An electrochemical method requiring reference electrode connection

Question 5

Microbiologically Influenced Corrosion (MIC) is most effectively monitored by:

Accepted Answer

Combining microbiological sampling, corrosion rate measurement, and biocide effectiveness evaluation

Answer

Electrical Resistance probes as the sole monitoring tool

Answer

pH measurement alone as the primary indicator

Answer

Ultrasonic thickness surveys conducted every 10 years

Question 6

When interpreting ER probe data, a sudden step increase in the probe reading followed by a plateau (stable value) most likely indicates:

Accepted Answer

A temporary corrosion upset event that has since subsided, leaving the probe at a higher cumulative loss

Answer

A calibration error in the measurement electronics

Answer

Cathodic protection becoming fully effective and arresting further corrosion

Answer

Scale or deposit build-up reducing the probe element cross-section

Question 7

What is the primary purpose of establishing a corrosion monitoring baseline during system commissioning?

Accepted Answer

To create a reference point for comparing future monitoring data and detecting deviations from normal behavior

Answer

To satisfy regulatory reporting requirements as the sole objective

Answer

To eliminate the need for future scheduled inspections

Answer

To calculate the as-built remaining design life of the new structure