GPT Corrosion Control & Cathodic Protection 3

Question 1

Per 49 CFR Part 192, how often must a technician inspect and test rectifiers on impressed current cathodic protection systems serving gas pipelines?

Accepted Answer

Every 2 months (six times per calendar year)

Answer

49 CFR 192.613 and 192.465 require that impressed current CP rectifiers be inspected and tested at least six times each calendar year, with intervals not exceeding 2½ months.

Question 2

Which soil characteristic most increases the external corrosion risk for a buried steel gas pipeline?

Accepted Answer

Low soil resistivity (below 1,000 ohm-cm)

Answer

Low soil resistivity indicates a highly conductive (often wet, clay-rich, or contaminated) environment that promotes electrochemical corrosion of buried metal.

Question 3

A direct current (DC) potential of -1.5 V (CSE) measured on a coated steel gas main could indicate:

Accepted Answer

Overprotection, which can cause hydrogen embrittlement or coating disbondment

Answer

Excessive negative potentials (overprotection) can cause hydrogen evolution at the pipe surface, leading to hydrogen embrittlement of high-strength steel and cathodic disbondment of coatings.

Question 4

Which document provides the industry standard guidelines for external corrosion control of underground or submerged metallic piping systems?

Accepted Answer

NACE SP0169 (now AMPP SP0169)

Answer

NACE SP0169 (now published under AMPP) is the primary industry standard for control of external corrosion on underground or submerged metallic piping systems.

Question 5

When a gas technician installs a new steel service line adjacent to an existing copper water service, what corrosion risk must be managed?

Accepted Answer

Galvanic corrosion if the two metals are electrically connected through soil or direct contact

Answer

If copper (more noble) and steel (more active) are in electrical contact in a moist soil environment, a galvanic cell forms and the steel will corrode preferentially.

(GPT) Gas Pipe Technician Certification Practice Test

(GPT) Gas Pipe Technician Certification Practice Test

GPT Corrosion Control & Cathodic Protection 3