Questions and Answers (Graded A+)
In complex structures, always select materials that are ____ each other in the galvanic
series that will exhibit ____ voltage differences - ANSWER-near, little to no
What is the first line of defense in corrosion control programs? - ANSWER-coating
If the structure is coated, it is necessary to protect only the metal exposed at ____ -
ANSWER-holidays
Pipeline coatings designed for underground use do not have good resistance to ____
light, so ____ is to be avoided - ANSWER-UV, sunlight
Coatings formulated from coal tar pitch or natural asphalt, reinforced with glass and a
felt wrapper, used less today because of toxicity - ANSWER-bituminous enamels
Coatings that consist of polyolefin or polyethylene extruded over butyl or asphalt mastic
adhesive, high impact resistance and resist holiday development - ANSWER-extruded
polyolefin and polyethylene
Coatings that consist of a primer, corrosion sealant inner layer, mechanical protective
outer layer backing (usually polyethylene or polybutylene), prone to disbonding if not
properly tensioned - ANSWER-tape coatings
Coatings that consist of powdered resin electrostatically sprayed onto heated pipe,
moisture absorption can be a problem - ANSWER-fusion boned epoxy (FBE)
Coatings that consist of liquid resin (epoxy) and a curing agent, resistant to impact and
abrasion damage - ANSWER-two-component liquid resin coatings (two part epoxy)
What is essential for the coating to bond properly to the metal? - ANSWER-proper
surface preparation and application (hot or cold)
What environmental conditions must be checked during initial inspection before coating
application? - ANSWER-temperature, humidity, dew point
What should be checked for visually during coating application? - ANSWER-disbonding,
damage, checking, cracking, chalking, etc. (check if reconditioning is required)
, Why are inhibitors added to liquids? - ANSWER-to change the characteristics of the
liquid or form protective films on the metal surface
How does sunlight exposure affect a coating? - ANSWER-changes porosity, brittle
(changes properties)
What are the following materials used for: heat shrink sleeves, hot and cold applied
tapes, two-component liquid resins, coal tar mastics, fusion bonded epoxy? - ANSWER-
girth weld coatings
If you have to use dissimilar metals, what must you do? - ANSWER-electrically isolate
them
It's better to install more test stations rather than fewer, but where should test stations
definitely be installed? - ANSWER-buried isolating fittings, crossings, electrical bonding
of joints
What are potential measurement test stations used to monitor? (3) - ANSWER-
effectiveness of CP, stray current effects, locate areas of active corrosion (no. 12 AWG
insulated wires, thermite-welded to pipe)
What are IR drop (current span) test station used for? - ANSWER-to measure
magnitude and direction of current flow on pipeline (pipeline acts as resistor, current
determine by measuring IR drop across span of test wires
What is the purpose of a casing? - ANSWER-support dynamic loads caused by road
traffic or trains to prevent harm to the pipe
Wherever possible, isolating joints should be installed.... - ANSWER-above grade (or
needs test station)
Coupons allow for ____ ____ ____ measurements without interrupting the rectifier, and
can measure protective current density of a ____ of known size - ANSWER-instant off
potential, known size
Do not use larger than a ____ charge for carbon steel pressure pipe when thermite
welding wires onto steel - ANSWER-15 gram
Underground mechanical connections are made with a ____ and a ____ epoxy for test
leads - ANSWER-clamp, conductive (not preferred, easily broken by corrosion)
The efficiency of a galvanic anodes depends on the ____ of the anode and the ____ to
which it is installed - ANSWER-alloy, environment
Anode efficiency is generally about ____ for Mg, ____ for Zn, and ____ for Al (but can
vary) - ANSWER-50%, 90%, 90% (range)