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AMPP Corrosion Technician practice questions

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Question 1Cathodic Protection

In a cathodic protection circuit, which electrode is the anode of the corrosion cell being protected?

  1. The auxiliary electrode in a test station
  2. The reference electrode
  3. The structure receiving protection
  4. The buried anode bed Correct answer.

Explanation

In cathodic protection, the buried anode bed is the anode of the deliberately created cell and corrodes, while the protected structure is forced to act as the cathode. The reference electrode is only a measuring tool and does not drive current.

Question 2Cathodic Protection

What is the primary purpose of cathodic protection on a buried steel pipeline?

  1. To raise the soil resistivity around the pipe
  2. To supply electrons so the steel stops acting as an anodic dissolution site Correct answer.
  3. To coat the pipe with a metallic barrier layer
  4. To increase the pipe-to-soil potential difference in the anodic direction

Explanation

Cathodic protection works by supplying electrons to the structure so that anodic dissolution reactions are suppressed. The structure becomes the cathode of the corrosion cell and corrosion current leaves the metal at protected areas.

Question 3Cathodic Protection

In a galvanic cathodic protection system, which metal is commonly used as the anode to protect buried steel?

  1. Platinum
  2. Stainless steel
  3. Copper
  4. Magnesium Correct answer.

Explanation

Magnesium is more active than steel and therefore serves as a sacrificial anode, dissolving preferentially while protecting the steel. Zinc and aluminum are also used, but copper, platinum, and stainless steel are not sacrificial to steel.

Question 4Cathodic Protection

Which of the following is a typical component of an impressed current cathodic protection system?

  1. A sacrificial magnesium bracelet
  2. A coating holiday detector
  3. A soil resistivity meter
  4. A transformer-rectifier Correct answer.

Explanation

An impressed current system uses an external DC power source, commonly a transformer-rectifier, to drive current from an inert anode to the structure. Sacrificial anodes belong to galvanic systems, and the other devices are survey instruments.

Question 5Cathodic Protection

A copper-copper sulfate reference electrode is most commonly used to measure which quantity in pipeline cathodic protection?

  1. Coating conductance
  2. Soil pH
  3. Pipe-to-soil potential Correct answer.
  4. Pipe wall thickness

Explanation

The copper-copper sulfate half-cell is the standard reference for measuring pipe-to-soil potential, which indicates whether the structure is cathodically protected. It does not measure wall thickness, pH, or coating conductance directly.

Question 6Cathodic Protection

Which criterion is widely used to judge that buried steel is cathodically protected, measured with a copper-copper sulfate reference electrode?

  1. A potential of exactly 0.00 V
  2. A potential of +0.85 V or more positive
  3. A potential of -0.30 V or more negative
  4. A potential of -0.85 V or more negative Correct answer.

Explanation

The widely accepted criterion for buried or submerged steel is a pipe-to-soil potential of -0.85 V (CSE) or more negative, provided the measurement is free of IR error. More positive values generally indicate incomplete protection.

Question 7Cathodic Protection

What does a close-interval survey (CIS) primarily measure along a pipeline?

  1. Pipe-to-soil potential at closely spaced intervals Correct answer.
  2. Coating thickness at welds
  3. Soil thermal conductivity
  4. Anode bed resistance

Explanation

A close-interval survey records pipe-to-soil potential at short, regular intervals to identify areas of low or inadequate protection. It does not measure coating thickness, thermal properties, or anode resistance.

Question 8Cathodic Protection

Which of the following best describes an electrolyte in a cathodic protection system?

  1. The insulating coating on the pipe
  2. The soil or water in contact with the structure Correct answer.
  3. The metallic path connecting anode and structure
  4. The DC power supply

Explanation

The electrolyte is the continuous conductive medium, such as soil or water, through which ionic current flows between the anode and the structure. The metallic path carries electronic current, and the coating is intended to be an insulator.

Question 9Cathodic Protection

An impressed current anode bed is discharging 2.0 A. If the soil resistivity around the bed is 2000 ohm-cm and the bed's effective resistance to remote earth is 1.5 ohms, what is the approximate voltage drop from the bed to remote earth?

  1. 1.5 V
  2. 2.0 V
  3. 4.5 V
  4. 3.0 V Correct answer.

Explanation

Ohm's law gives the voltage drop across the anode bed's resistance: V = I × R = 2.0 A × 1.5 ohms = 3.0 V. The soil resistivity value is not needed for this calculation.

Question 10Cathodic Protection

A structure is polarized to -0.80 V (CSE) with the CP current on and reads -0.75 V (CSE) immediately after the current is interrupted. What does the instant-off reading indicate?

  1. The reference electrode is faulty
  2. The IR component was about 0.05 V and the polarized potential is about -0.75 V Correct answer.
  3. The anode bed is disconnected
  4. The structure is fully protected because the on-potential is more negative than -0.70 V

Explanation

Interrupting the current removes the IR drop, so the instant-off reading approximates the true polarized potential. The difference between on and instant-off readings (0.05 V here) is the IR component.

Question 11Cathodic Protection

Which condition would most likely increase the current required from a cathodic protection system on a coated pipeline?

  1. A decrease in the number of pipe joints
  2. An increase in the reference electrode distance
  3. An increase in coating holiday area Correct answer.
  4. A decrease in soil moisture content

Explanation

Coating holidays expose bare steel to the electrolyte, increasing the current demand needed to polarize those areas. Reference electrode distance does not change current demand, and drier soil generally reduces current flow.

Question 12Cathodic Protection

In a galvanic anode system, what happens to the magnesium anode over time?

  1. It is consumed by oxidation and eventually requires replacement Correct answer.
  2. It becomes more noble and stops working
  3. It converts into a reference electrode
  4. It absorbs electrons from the pipe

Explanation

Sacrificial anodes protect the structure by corroding themselves; the magnesium is oxidized and consumed over time. Once the anode is depleted, protection is lost and the anode must be replaced.

Question 13Cathodic Protection

Why is a rectifier output typically adjusted rather than left at a fixed setting?

  1. To keep the pipe-to-soil potential within the protection range as conditions change Correct answer.
  2. To reduce the number of anodes in the bed
  3. To increase the coating thickness over time
  4. To change the reference electrode type

Explanation

Soil conditions, coating degradation, and stray current interference change over time, so rectifier output is adjusted to maintain adequate but not excessive polarization. Excessive current can cause coating damage and interference.

Question 14Cathodic Protection

During a structure-to-electrolyte potential measurement, the reference electrode should be placed where?

  1. Directly on the pipe surface after excavation
  2. At the rectifier cabinet only
  3. In contact with the electrolyte as close as practical to the structure Correct answer.
  4. At the anode bed

Explanation

The reference electrode must contact the electrolyte near the structure so the measured potential reflects the pipe-to-soil interface with minimal voltage drop through the soil. Placement far from the structure introduces error.

Question 15Cathodic Protection

A pipe-to-soil potential reads -0.95 V (CSE) with the CP current on, but the instant-off reading is -0.78 V (CSE). What is the most reasonable conclusion?

  1. The reference electrode is reversed
  2. The soil resistivity is too high to measure
  3. The true polarized potential is below the criterion and protection may be inadequate Correct answer.
  4. The pipe is protected because the on-reading is more negative than -0.85 V

Explanation

The instant-off reading approximates the true polarized potential, and -0.78 V is more positive than the -0.85 V criterion. The on-reading of -0.95 V includes IR error and overstates protection.

Question 16Cathodic Protection

Which factor most strongly influences the resistance of a single vertical anode to earth?

  1. The soil resistivity and the anode's dimensions and depth Correct answer.
  2. The rectifier's AC input voltage
  3. The anode's alloy composition
  4. The pipe coating type

Explanation

Anode-to-earth resistance depends primarily on soil resistivity and the anode's geometry, especially length and diameter. Alloy composition affects the electrochemical reaction but not the geometric resistance to earth.

Question 17Cathodic Protection

A galvanic anode is rated at 1000 A·h of capacity and the system draws 0.05 A continuously. Approximately how long will the anode last, ignoring efficiency and utilization factors?

  1. 5000 hours
  2. 2000 hours
  3. 20000 hours Correct answer.
  4. 500 hours

Explanation

Life is capacity divided by current: 1000 A·h ÷ 0.05 A = 20,000 hours. Real designs apply efficiency and utilization factors, which would shorten the calculated life.

Question 18Cathodic Protection

Which situation indicates that a cathodic protection system may be causing stray current interference on a foreign structure?

  1. The foreign structure shows a potential shift toward more negative values when the CP current is interrupted
  2. The foreign structure's coating resistance increases
  3. The foreign structure shows a potential shift toward more positive values when the CP current is turned on Correct answer.
  4. The foreign structure's reference electrode reads zero

Explanation

Stray current interference is identified when a foreign structure's potential becomes more positive (anodic) due to current picked up and discharged by the CP system. This can accelerate corrosion on the foreign structure.

Question 19Cathodic Protection

In a pipeline CP system, what is the purpose of an insulating flange or isolating joint?

  1. To electrically isolate a section of pipeline from other metallic structures Correct answer.
  2. To improve coating adhesion
  3. To increase the pipe's electrical resistance to the soil
  4. To connect the pipe directly to the anode bed

Explanation

Isolating joints break the metallic path between pipeline sections or between the pipe and other structures, which helps confine CP current and control interference. They do not affect soil resistance or coating adhesion.

Question 20Cathodic Protection

A test station reads -0.60 V (CSE) on a coated pipeline with a rectifier running. What is the most appropriate first action?

  1. Increase the rectifier output without checking anything
  2. Immediately replace the entire anode bed
  3. Assume the pipe is protected and take no action
  4. Investigate possible causes such as a failed rectifier, high-resistance connection, or coating damage Correct answer.

Explanation

A reading more positive than the protection criterion indicates inadequate protection, but the cause must be identified before corrective action. Troubleshooting should check the rectifier, connections, and coating condition.

Question 21Cathodic Protection

Which of the following statements about the -0.85 V (CSE) criterion is most accurate?

  1. It applies only to copper structures
  2. It requires the CP current to be switched off
  3. It guarantees protection under all soil conditions without exception
  4. It is a generally accepted criterion for buried or submerged steel but must be applied with attention to IR error Correct answer.

Explanation

The -0.85 V criterion is a widely used benchmark for steel, but valid application requires accounting for IR drop, typically by using instant-off or current-interrupted readings. It is not a universal guarantee for all conditions.

Question 22Cathodic Protection

A CP system on a coated pipeline shows high current output but potentials remain below criterion. Which combination of causes is most consistent with this observation?

  1. A reference electrode placed too close to the pipe
  2. Severe coating damage plus a shorted or failed isolating joint Correct answer.
  3. A perfectly intact coating plus low soil resistivity
  4. An oversized anode bed plus low current demand

Explanation

High current with poor potentials suggests current is being lost to bare steel or to unintended metallic paths such as a shorted isolating joint. Both conditions divert current from the intended protected surface.

Question 23Cathodic Protection

In a current-interrupted survey, the instant-off potential is measured a short time after interruption. Why is a very short delay used rather than a long one?

  1. To allow the rectifier to restart
  2. To let the reference electrode stabilize at a new location
  3. To measure the AC ripple on the pipe
  4. To capture the potential before significant depolarization occurs Correct answer.

Explanation

Immediately after interruption, the IR component disappears but the structure has not yet depolarized significantly, so the instant-off reading approximates the polarized potential. A long delay would allow depolarization and yield a less negative, misleading value.

Question 24Cathodic Protection

Two adjacent pipelines share a common corridor. Pipeline A is cathodically protected and pipeline B is bare. Which effect is most likely on pipeline B?

  1. Pipeline B will increase the resistance of pipeline A's anode bed
  2. Pipeline B will pick up current near A's anodes and discharge it elsewhere, causing accelerated corrosion at discharge points Correct answer.
  3. Pipeline B will become more negative everywhere and need no protection
  4. Pipeline B will act as a reference electrode

Explanation

Stray current from A's CP system can enter B where the potential is more negative and leave B at discharge areas, where the anodic reaction accelerates corrosion. This is why interference surveys and mitigation are required in shared corridors.

Question 25Cathodic Protection

A rectifier is rated to deliver 10 A at 20 V DC. If the load resistance of the CP circuit is 4 ohms, what current will the circuit draw at that voltage, and is it within the rectifier's rating?

  1. 10 A, at the rating limit
  2. 2.5 A, within the rating
  3. 40 A, exceeding the rating
  4. 5 A, within the rating Correct answer.

Explanation

Ohm's law gives I = V / R = 20 V / 4 ohms = 5 A, which is below the 10 A rating. The circuit will operate within the rectifier's capability.

Question 26Cathodic Protection

Which reference electrode is most commonly used for structure-to-electrolyte potential measurements in cathodic protection?

  1. Zinc electrode
  2. Silver-silver chloride electrode
  3. Saturated calomel electrode
  4. Copper-copper sulfate electrode Correct answer.

Explanation

The copper-copper sulfate electrode (CSE) is the standard reference for CP potential measurements in soil and water because it is rugged, stable, and widely accepted. Other electrodes are used in specific environments but are not the general field standard.

Question 27Cathodic Protection

What is the primary purpose of cathodic protection?

  1. To reverse the polarity of the metal structure
  2. To provide a protective coating on the metal surface
  3. To reduce the corrosion rate of a metal surface to an acceptable level Correct answer.
  4. To increase the electrical resistance of the electrolyte

Explanation

Cathodic protection works by making the metal the cathode of a corrosion cell, which suppresses anodic dissolution and lowers the corrosion rate. It does not alter the electrolyte resistance, apply a coating, or reverse polarity.

Question 28Cathodic Protection

Which type of cathodic protection system uses an external power source and inert anodes?

  1. Impressed current system Correct answer.
  2. Galvanic anode system
  3. Sacrificial anode system
  4. Stray current system

Explanation

Impressed current systems use a rectifier or other DC power source to drive current from inert anodes to the structure. Galvanic (sacrificial) systems rely on the natural potential difference between metals and do not use an external power source.

Question 29Cathodic Protection

What is the minimum potential required for cathodic protection of buried steel in soil, measured with a copper-copper sulfate electrode?

  1. -0.85 V Correct answer.
  2. -0.75 V
  3. -0.65 V
  4. -0.95 V

Explanation

The widely accepted criterion for buried steel is a potential of -0.85 V (CSE) or more negative, measured with the current applied. This value corresponds to the protection potential for steel in typical soil conditions.

Question 30Cathodic Protection

A galvanic anode is made of a metal that is more active than the structure it protects. What is this relationship called?

  1. Electrolytic series
  2. Potentiostatic series
  3. Amphoteric series
  4. Galvanic series Correct answer.

Explanation

The galvanic series lists metals in order of their corrosion potential in a given environment. The more active metal becomes the anode and corrodes preferentially, protecting the more noble metal.

Question 31Cathodic Protection

In a galvanic anode system, what determines the amount of current that will flow?

  1. The potential difference between the anode and structure divided by the circuit resistance Correct answer.
  2. The temperature of the electrolyte only
  3. The length of the anode lead wire
  4. The color of the anode material

Explanation

By Ohm's law, current equals the driving voltage (potential difference between anode and cathode) divided by the total circuit resistance. The lead wire length, color, and temperature alone do not determine current.

Question 32Cathodic Protection

What is the purpose of a rectifier in an impressed current cathodic protection system?

  1. To convert direct current to alternating current
  2. To store electrical energy for later use
  3. To measure the structure-to-electrolyte potential
  4. To convert alternating current to direct current Correct answer.

Explanation

A rectifier takes AC power from the grid and converts it to the DC needed for cathodic protection. It does not invert DC to AC, store energy, or measure potential.

Question 33Cathodic Protection

Which soil property has the greatest effect on the current required for cathodic protection of a bare pipeline?

  1. Soil pH
  2. Soil resistivity Correct answer.
  3. Soil color
  4. Soil temperature

Explanation

Soil resistivity directly affects the resistance of the current path between anode and structure; lower resistivity means more current can flow for a given voltage. pH, color, and temperature have lesser or indirect effects.

Question 34Cathodic Protection

What is the purpose of a close-interval survey (CIS) in cathodic protection?

  1. To determine the flow rate of the pipeline
  2. To inspect the coating for holidays
  3. To measure the resistivity of the soil
  4. To identify areas of inadequate protection along a pipeline Correct answer.

Explanation

A CIS measures structure-to-electrolyte potentials at closely spaced intervals to find locations where protection is insufficient. It does not measure soil resistivity, flow rate, or directly detect coating holidays.

Question 35Cathodic Protection

A structure-to-electrolyte potential is measured as -1.20 V (CSE) with the CP current on. What does this reading indicate?

  1. The structure is not protected
  2. The structure is protected but at risk of corrosion
  3. The reference electrode is faulty
  4. The structure may be overprotected Correct answer.

Explanation

A potential more negative than about -1.20 V (CSE) on steel can indicate overprotection, which may cause coating disbondment or hydrogen embrittlement. It does not mean the structure is unprotected or that the electrode is necessarily faulty.

Question 36Cathodic Protection

What is the primary function of a dielectric coating on a pipeline in a cathodic protection system?

  1. To increase the electrical conductivity of the pipe
  2. To provide a path for stray currents
  3. To reduce the current required for protection Correct answer.
  4. To act as a sacrificial anode

Explanation

A dielectric coating isolates the pipe from the electrolyte, greatly reducing the exposed metal area and thus the current needed to polarize the structure. It does not increase conductivity, provide a stray current path, or act as an anode.

Question 37Cathodic Protection

A cathodic protection rectifier is adjusted to increase the current output. What is the most likely effect on the structure-to-electrolyte potential?

  1. The potential fluctuates randomly
  2. The potential remains unchanged
  3. The potential becomes more positive
  4. The potential becomes more negative Correct answer.

Explanation

Increasing CP current increases cathodic polarization, driving the structure potential in the negative direction. This is the basis for adjusting rectifier output to achieve protection criteria.

Question 38Cathodic Protection

What is the purpose of an insulating flange in a cathodic protection system?

  1. To measure the current flowing in the pipeline
  2. To provide a low-resistance path for CP current
  3. To electrically isolate a protected structure from other metallic structures Correct answer.
  4. To act as a backup anode

Explanation

Insulating flanges break electrical continuity between a protected pipeline and adjacent structures, preventing CP current from draining away and isolating the protected section. They do not provide a low-resistance path, measure current, or act as anodes.

Question 39Cathodic Protection

A pipeline is protected by an impressed current system. A nearby unprotected pipeline is found to have a potential shift in the negative direction. What is the most likely cause?

  1. Failure of the reference electrode
  2. Increased soil resistivity
  3. Corrosion of the unprotected pipeline
  4. Stray current interference from the protected pipeline Correct answer.

Explanation

Stray current from the protected pipeline can enter the unprotected pipeline, causing a negative potential shift where it picks up current. This indicates interference that may require mitigation.

Question 40Cathodic Protection

In a current-interrupted CP survey, why is the instant-off potential measured immediately after interrupting the current?

  1. To check the rectifier output voltage
  2. To eliminate the voltage drop in the soil and measure the polarized potential Correct answer.
  3. To determine the soil resistivity
  4. To measure the current flowing through the reference electrode

Explanation

The instant-off potential removes the IR drop caused by CP current flowing through the soil, revealing the true polarized potential of the structure. This is essential for accurate assessment of protection.

Question 41Protective Coatings

Which surface preparation standard is most commonly specified for abrasive blast cleaning to a near-white finish?

  1. SSPC-SP 2
  2. SSPC-SP 7 / NACE No. 4
  3. SSPC-SP 3
  4. SSPC-SP 10 / NACE No. 2 Correct answer.

Explanation

Near-white blast cleaning is designated SSPC-SP 10, which is equivalent to NACE No. 2. It removes nearly all mill scale, rust, and coating, leaving only light staining. The other listed standards describe brush-off blast, hand tool, and power tool cleaning.

Question 42Protective Coatings

What does the term 'anchor profile' describe on a prepared steel surface?

  1. The chemical composition of the steel
  2. The microscopic surface roughness created by abrasion Correct answer.
  3. The ambient dew point at application
  4. The thickness of the applied primer

Explanation

Anchor profile is the roughness pattern produced by blasting or other abrasion that gives the coating a mechanical key. It is measured in mils or micrometers and is distinct from cleanliness. Coating thickness, dew point, and steel chemistry are unrelated properties.

Question 43Protective Coatings

A coating is described as having a 'barrier' protective mechanism. What does this mean?

  1. It relies on sacrificial galvanic action
  2. It physically blocks moisture and oxygen from reaching the steel Correct answer.
  3. It chemically converts rust into a stable layer
  4. It releases corrosion-inhibiting ions into the electrolyte

Explanation

Barrier coatings protect by limiting permeation of water, oxygen, and ions to the substrate. Inhibitive coatings release passivating species, and sacrificial coatings act galvanically. Rust converters chemically alter corrosion products rather than acting as barriers.

Question 44Protective Coatings

Which environmental measurement indicates the temperature at which moisture begins to condense from the air onto a surface?

  1. Ambient air temperature
  2. Wet bulb depression
  3. Relative humidity
  4. Dew point Correct answer.

Explanation

Dew point is the temperature at which air becomes saturated and condensation begins. Coating should not be applied when the steel temperature is at or near the dew point. Relative humidity and wet bulb depression are related measures but do not directly state the condensation temperature.

Question 45Protective Coatings

What is the primary purpose of adding a thinner to a coating?

  1. To improve the color match
  2. To accelerate the curing reaction
  3. To increase the cured film thickness
  4. To adjust viscosity for the application method Correct answer.

Explanation

Thinners reduce viscosity so the coating can be applied by the chosen method and flow out properly. They generally do not increase film build and can reduce it if over-thinned. Cure acceleration and color are controlled by other formulation components.

Question 46Protective Coatings

Which coating type cures by reacting with moisture in the air?

  1. Alkyd enamel
  2. Epoxy polyamide
  3. Chlorinated rubber
  4. Moisture-cure polyurethane Correct answer.

Explanation

Moisture-cure polyurethanes rely on atmospheric moisture to complete the isocyanate reaction. Epoxy polyamides cure by chemical reaction between resin and hardener. Chlorinated rubber and alkyds cure largely by solvent evaporation and oxidative crosslinking, respectively.

Question 47Protective Coatings

What is the typical consequence of applying a coating over a surface contaminated with soluble salts?

  1. Premature blistering and undercutting of the film Correct answer.
  2. Increased adhesion of the coating
  3. Improved color retention
  4. Faster cure of the coating

Explanation

Soluble salts draw moisture through the film by osmosis, causing blistering and loss of adhesion. They do not improve adhesion or cure and have no bearing on color retention. Removal of salts is a key reason for washing after blasting.

Question 48Protective Coatings

Which instrument is used to measure the dry film thickness of a coating on steel?

  1. Wet film comb
  2. Surface profile comparator
  3. Magnetic pull-off gauge Correct answer.
  4. Holiday detector

Explanation

Magnetic pull-off and electromagnetic gauges measure dry film thickness on ferrous substrates. Holiday detectors find discontinuities, profile comparators assess roughness, and wet film combs measure thickness before curing.

Question 49Protective Coatings

A coating is specified to be applied at 8 mils dry film thickness but the contractor applies 5 mils. What is the most likely consequence?

  1. Higher resistance to abrasion
  2. Improved adhesion to the substrate
  3. Faster cure throughout the film
  4. Reduced barrier protection and shorter service life Correct answer.

Explanation

Under-film-build reduces the barrier and can shorten service life, especially for immersion or severe exposure. Thinner films do not inherently improve adhesion, cure, or abrasion resistance. Film build must meet the specification for the intended protection.

Question 50Protective Coatings

During inspection, the steel temperature reads 45°F and the dew point is 42°F. What is the appropriate action?

  1. Proceed and apply a thicker coat to compensate
  2. Proceed because the steel is above the dew point
  3. Proceed but add extra thinner
  4. Postpone application until the steel temperature rises sufficiently above the dew point Correct answer.

Explanation

Coating should not be applied when the surface temperature is within about 5°F (3°C) of the dew point, because condensation risk is high. Here the margin is only 3°F, so application should be postponed. Thinning or thickening does not correct condensation risk.