AMPP Cathodic Protection Specialist (CP4) Practice Questions — 10 Free (2026)

Why are excavation findings fed back into the survey programme?

• A. Because findings determine the criterion applied to the structure thereafter in every case without exception
• B. Because findings establish the calibration status of the survey instruments
• C. Because findings determine the reference electrode type used in later work
• D. Because findings determine the depth of cover to be replaced on the line
• E. Because comparing what was predicted with what was found calibrates the interpretation used everywhere else ✓

Knowing which signatures corresponded to real damage sharpens every subsequent prioritisation decision. Criteria, instrument calibration, electrode selection and cover depth are not affected. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 1.3

Why is an electrical resistance probe used in some monitoring installations?

• A. Because the probe sets the wall thickness of the structure
• B. Because the probe sets the coating colour of the structure
• C. Because the probe sets the internal pressure of the structure
• D. Because metal loss on a thin element raises its resistance ✓
• E. Because the probe sets the calibration of the survey instruments

The probe measures actual metal loss rather than inferring protection from a potential. Wall thickness, colour, pressure and calibration are unaffected. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 2.1

Why must a mitigation design be verified by measurement after installation?

• A. Because verification determines the criterion applied to both structures, since nothing else is thought to bear on the question
• B. Because the design rests on assumptions about resistances and potentials that only field measurement can confirm ✓
• C. Because verification establishes the calibration interval of instruments
• D. Because verification determines the reference electrode type used later
• E. Because verification determines the depth of cover over both structures

Achieved bond current and the resulting potentials on both structures either confirm the design or show that the resistance needs changing. Criteria, calibration intervals, electrode selection and cover depth are not established by the verification. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 3.1

Why do criteria differ for aluminium, copper alloys and reinforced concrete?

• A. Because those materials are always installed at a different burial depth
• B. Because those materials cannot be cathodically protected at all in practice, since nothing else is thought to bear on the question
• C. Because those materials require the same criterion as steel everywhere
• D. Because those materials are used only above ground and never buried
• E. Because each has its own potentials, its own susceptibilities and its own damage mechanisms at excessive polarisation ✓

Aluminium is attacked by alkalinity, concrete has its own criteria based on shift and depolarisation, and copper alloys have their own values. Burial depth, an inability to protect them, identical criteria and above-ground use are all incorrect. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 5.2

A circuit has a groundbed of 2.2 ohms, cables of 0.5 ohms and a structure resistance of 0.1 ohms. What driving voltage gives 10 A?

• A. 5.0 V
• B. 22.0 V
• C. 28.0 V ✓
• D. 35.0 V
• E. 280.0 V

The three resistances are added and the total is multiplied by the required current. Using only the groundbed value, or omitting the cables, gives the smaller answers. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 7.2

Why is a communications failure on a remote monitoring system treated as a fault?

• A. Because a silent unit gives no assurance at all ✓
• B. Because the failure determines the criterion applied to the structure
• C. Because the failure establishes the calibration of the field instruments
• D. Because the failure determines the reference electrode type used later
• E. Because the failure determines the depth of cover over the structure

Absence of data is not evidence of protection, so a lost link is followed up rather than assumed benign. Criteria, calibration, electrode selection and cover depth are not the reason. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 6.3

Why does a passive film reduce corrosion rate so dramatically?

• A. Because the film is thick enough to exclude the electrolyte physically
• B. Because the film impedes the anodic reaction ✓
• C. Because the film reverses the polarity of the metal in that environment
• D. Because the film conducts protective current directly into the metal
• E. Because the film prevents oxygen reaching the metal surface entirely

Passivity is a kinetic effect, since the thin film suppresses metal dissolution even though thermodynamics would still favour it. Physical exclusion, polarity reversal, conduction and complete oxygen exclusion are all incorrect. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 4.1

Why is a secondary containment liner a design constraint for tank floor protection?

• A. Because the liner conducts protective current to the plate above it
• B. Because the liner raises the temperature of the plate above it in service
• C. Because it isolates the plate from the ground ✓
• D. Because the liner prevents the tank from being located electronically
• E. Because the liner reverses the polarity of any current reaching the plate

An impermeable liner cuts off any anode installed below it, so the whole system must sit inside the containment. Conduction, temperature, locating and polarity reversal are all incorrect. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 6.4

Why is a test facility provided at each anode or anode group?

• A. Because the output must be measurable ✓
• B. Because the facility supplies the driving voltage that the anode requires
• C. Because the facility determines the criterion applied to the structure
• D. Because the facility determines the reference electrode type used later
• E. Because the facility determines the depth of cover over the anode itself

Without an accessible connection the anode cannot be measured, switched or replaced, so the system becomes unmanageable. Supplying driving voltage, criteria, electrode selection and cover depth are all incorrect. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 6.1

Eight identical anodes of 16 ohms each are connected in parallel with no interference between them. What is the combined resistance?

• A. 1.0 ohm
• B. 2.0 ohm ✓
• C. 8.0 ohm
• D. 16.0 ohm
• E. 128.0 ohm

For identical resistances in parallel the combined value is one resistance divided by the number, so 16 divided by 8 gives 2.0 ohms, before any allowance for mutual interference. Halving, quoting one anode or multiplying gives the other answers. AMPP CP 4 Cathodic Protection Specialist student manual and exam preparation guide, 1.1