Chapter 3 and 4 Flashcards
In a rectifier, the transformer alternating current (AC) to direct current (DC)
False
The positive lead of the rectifier is always connected to the structure
False
Magnesium, zinc and aluminum are common ICCP anodes
False
The Department of Transportation requires use of CP on residential propane tanks
False
CP can be used him to come structures, but not submerged structures
False
Solar panels rectify AC to DC
False
Galvanic and impress current cathodic protection frequently uses the same metals for anodes.
False
Per DOT guidelines, water lines must be cathodically protected
False
CP cannot be used to protect aboveground storage tanks
It depends
Which reference is best suited for soil
CSE
Positive lead of the voltmeter should be placed on the structure during the structure to electrolyte reading
True
Standard hydrogen electrodes are commonly used in the field
False
The three criteria recommended by NACE are
850 applied 850 off 100 mV of polarization
The native potential can be calculated by
The polarization from the polarized potential
IR drop is calculated by subtracting
Polarized potential from the applied potential
IR drop must be considered for the -850 mV polarized criteria
False
IR drop must be considered for the -850mV applied criteria
True
I R drop must be considered for the 100 mV polarization criteria
False
-850mV Applied is the most widely used criteria
True
The driving voltage of the cathodic protection system must be greater than what to provide effective cathodic protection
Driving voltage of corrosion cell
The sole purpose of the cathodic protection ground bed is too?
Discharge current
When cathodic protection current is applied to a structure, which direction does the potential of the structure shift
Active direction also known as negative direction
Two methods utilized to produce the Cathodic protection current
Impressed current and galvanic anodes
Define CSE
Copper – copper sulfate electrode the most common reference electrode used to take pipe just saw potential readings
Define pipe-to-soil potential
The potential of a pipeline at a given location compared to a reference electrode
Define the on potential
The potential measurement is taken with the CP system energized
Define off or instant-off potential
The potential measurement is taken with the CP system not energized also known as polarized potential
How does the use of underground pipe line coatings affect the current requirement to achieve cathodic protection
Hey well coated pipe will need less current to protect the uncoated parts of the pipe
What is a possible to protect more miles of large diameter pipe from a single cathodic protection installment than small diameter pipe lines
Per Ohm’s law current flow is inversely proportional to total resistance large diameter pipe has a low resistance than small diameter pipe
Cathodic despond meant can be avoided if the off-potentials are Below what level
-1.1 V (CSE)
Which brownbag construction method will produce a small area for protection provide the least effective on the on the potential compared to remote earth
Close ground bed
A plastic material loosely wrapped around a pipeline that blocks the effectiveness of the cathodic protection current is an example of which type of shielding
Insulating barrier
A sort of pipeline casing on the pipeline Road crossing which blocks the effectiveness of the cathodic protection current is an example of which shielding
Metallic shielding
It is a good idea to ensure that reinforcing wire in concrete be allowed to contact the underlying steel which is under cathodic protection to avoid shielding problems. T or F
False
What is cathodic corrosion and give an example
Too much CP applied the alkalinity of the aluminum pipe may become sufficient to break down passive films
Which type of cathodic protection system is most likely to cause stray current damage
Impressed
Three primary criteria used for cathodic protection of underground or submerged steel piping
-850 mV with CP applied, -850 mV polarized, 100 mV polarization
Which of the three criteria is the most widely used for steel structures
-850 mV CSE applied
What is the native potential
Potential structure before CP is ever applied
How can damage be avoided from hydrogen generated in the cathodic protection process
Avoid potential’s more negative the -1.05 to -1.1 mV CSE polarized
What is a polarized potential
Potential across the structure electrolyte interface that is the sum of the corrosion potential and the cathodic polarization
How was polarized potential measured
Immediately after all current sources have been interrupted
How to measure the formation of cathodic polarization for the 100 mV criteria
- Measure the native potential, 2. Apply CP and allow structure the polarized. 3. Measure the polarized instant off potential. 4. Find the difference of the native and polarized potentials. 5. If greater than 100 mV, criteria is met
Describes how to measure the decay of cathodic polarization for the 100 mV criteria
Measure the polarized potential (instant off). De-energize CP system and allow structure to depolarize. Measure the depolarize potential. Find the difference from the polarized and depolarized potentials. If greater than 100 mV, criteria is met
Which of the following criteria can also be used on metal other than steel
The 100 mV polarization
Why should the 100 mV polarization criteria not be used in areas where intergranular external SCC is suspected
Criteria my place the structure in the range for cracking which is between the native and the -850 mV CSE
Which cathodic protection criteria requires the side drain procedure
Net protective current
Which cathodic protection criteria are used for copper
The 100 mV polarization
Which cathodic protection criteria are used for copper if it is electrically connected to steal
-850 mV CSE with CP applied and -850 mV CSE polarized potential
Which cathodic protection criteria is most commonly used for well coated structures that can be cost prohibitive for poorly coated or bear structures
-850 mV CSC with CP applied
Which cathodic protection criteria is measured directly after the interruption of all current sources
-850 mV CSE polarized potential
According to the text which four criteria should not be utilized in areas of stray current activity
300 mV shift, E log I, 100 mV polarization, Net protective current
