Free O-CAT Practice Questions

Question 1

Small carbon-steel bolts fasten a large, bare stainless-steel plate in a seawater-wetted assembly. The stainless steel is cathodic to the carbon steel under these conditions. During maintenance, only the bolts are painted, leaving a few small coating holidays; electrical contact between the metals remains intact. What is the principal weakness of this repair?

Accepted Answer

The holidays concentrate anodic attack into a small steel area coupled to a large cathode.

Answer

Painting the bolts enlarges the active anodic area and spreads corrosion.

Answer

Painting the heads interrupts the circuit despite the remaining metal-to-metal contact.

Answer

The stainless plate becomes the anode and takes over the corrosion previously occurring on the steel bolts.

Question 2

A coating specification invokes SSPC-PA 2 Restriction Level 3 for a dry-film thickness of 200-300 µm, with no separate limits on individual gage readings. In one test area, the five spot averages are 185, 220, 235, 250, and 260 µm; the area average is 230 µm. A valid individual reading of 125 µm contributes to the 185 µm spot. How should these DFT results be dispositioned?

Accepted Answer

Accept the area: its spot and area averages satisfy Level 3, despite the low individual reading.

Answer

Reject the area because the 125 µm reading is below 80% of the specified minimum.

Answer

Require additional coating at the 185 µm spot before the area can be accepted.

Answer

Discard the 125 µm reading and recalculate its spot average before making a decision.

Question 3

At a repair-planning meeting, four findings are being ranked. None presents an immediate access or leakage hazard. Which finding most clearly needs an integrity disposition rather than a coating-only repair?

Accepted Answer

Less than 1% visible rust on a load-bearing brace, with a reproducible local thickness of 4.6 mm against an engineering-specified 6.0 mm minimum.

Answer

Widespread chalking on a pipe rack whose coating remains adherent and whose measured steel thickness meets the applicable requirements.

Answer

Scattered rust breakthrough on a stair stringer whose cleaned surface and thickness survey show no loss below its required section.

Answer

Blistered coating on a deck beam whose exposed substrate has been examined and meets the required thickness throughout the affected area.

Question 4

A submerged riser is designed to share a jacket's galvanic cathodic-protection system. Valid potentials are -0.96 V on the jacket and -0.62 V on the riser, both versus Ag/AgCl/seawater. The intended bonding strap is broken, and testing confirms no other metallic connection between riser and jacket. The jacket anodes retain useful material. What should the corrective work address first?

Accepted Answer

Restore the designed electrical bond and then verify the riser's protection potential.

Answer

Replace the jacket anodes to increase the current available through seawater.

Answer

Recoat the accessible jacket steel to reduce its current demand before repairing the bond.

Answer

Move the existing anodes closer to the riser while retaining its electrical isolation.

Question 5

A repeat CP survey records -0.97 V versus copper/copper sulfate at a steel location previously recorded as -0.90 V versus Ag/AgCl/seawater. Instrument checks and measurement locations are satisfactory in both surveys. The report writer is asked whether protection has improved. Which conclusion is supportable?

Accepted Answer

No trend is established until the readings are placed on a common reference-electrode basis.

Answer

The 70 mV negative shift establishes that cathodic protection has improved.

Answer

Discard the earlier result; measurements made with different reference electrodes cannot be reconciled.

Answer

Their average should become the new baseline because both surveys used verified instruments.

Question 6

A carbon-steel clamp holds a carbon-steel pipe. Seawater remains beneath the clamp, where oxygen is depleted, while the adjacent wet pipe surface is well aerated. The metals are electrically continuous. In the resulting differential-aeration cell, where is anodic metal loss expected to concentrate?

Accepted Answer

Beneath the clamp, where the retained seawater is oxygen-poor.

Answer

On the oxygen-rich exposed pipe surface, where oxygen is most available.

Answer

Equally on both surfaces, because the metals are the same alloy.

Answer

Only along the clamp edge, because metal farther into the oxygen-depleted crevice is protected.

Question 7

During an external inspection near a sour-fluid drain, an inspector's personal monitor alarms at 120 ppm H2S. The rotten-egg odor noticed moments earlier has faded. The inspector is not wearing respiratory protection. What is the immediate response?

Accepted Answer

Withdraw along the designated escape route and notify the control room under the emergency plan.

Answer

Remain outside the drain enclosure while a coworker brings a second monitor to confirm the reading.

Answer

Put on an H2S-rated cartridge respirator and finish the short inspection before leaving the area.

Answer

Wait briefly and retest because the fading odor suggests that the gas plume has passed.

Question 8

Ultrasonic thickness readings on an isolated pipe jump between 4.8 and 9.1 mm over loose, flaking scale, without a stable back-wall echo. The gauge correctly measures a known reference block before and after these attempts. The pipe's nominal wall is 8.0 mm. How should the technician resolve this measurement?

Accepted Answer

Prepare the surface by the approved method, restore reliable coupling, and repeat the local examination.

Answer

Record the average of the fluctuating values, since the reference-block checks confirm the gauge is accurate.

Answer

Reject the pipe using 4.8 mm as its confirmed minimum, without repeating the examination after surface preparation.

Answer

Adjust the sound velocity until the pipe reads 8.0 mm, then use that setting to complete the survey.

Question 9

A Level I assessment uses the historical MMS A-B-C maintenance-horizon grading system. Engineering review finds no current hazard and no maintenance need within the next 12 months, but coating maintenance will be required in 18 months. The coordinator proposes grade A because production can continue. Which grading decision fits these findings?

Accepted Answer

Use grade B; the maintenance need falls within the three-year horizon.

Answer

Keep grade A; continued production establishes that the facility is in good condition.

Answer

Use grade C; any identified need for coating maintenance makes the condition poor.

Answer

Withhold a grade until the visible-rust percentage has been converted to a numerical coating rating.

Question 10

Powder matching the coating color rubs off a sun-exposed epoxy finish on an atmospheric pipe rack. The remaining coating is adherent, steel is not exposed, and the assessment finds no significant metal loss. The owner wants to restore the weathered finish. Which maintenance scope best meets that request?

Accepted Answer

Remove the chalking by approved cleaning and prepare for a compatible exterior topcoat.

Answer

Strip the entire coating system to bare steel because the powder proves loss of adhesion at the substrate.

Answer

Apply the exterior topcoat directly over the powder so the new film binds the loose material in place.

Answer

Defer surface work until rust breakthrough appears, using visible steel corrosion as the sole maintenance trigger.

Free O-CAT Practice Questions

Domain 1: Evaluate platform corrosion system (17-22%)

Question 1

Question 2

Domain 2: Testing Methods (16-21%)

Question 3

Question 4

Domain 3: Safety (1-4%)

Question 5

Domain 4: Systems and requirements to collect information on platforms (12-17%)

Question 6

Domain 6: Primary corrosion protection systems (12-17%)

Question 7

Domain 7: Role of BSEE and A-B-C- grading system for reporting (1-4%)

Question 8

Domain 8: General Knowledge (24-28%)

Question 9

Question 10

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