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AMPP Marine Coatings practice questions

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Question 1Marine coatings inspection fundamentals

Which property of a coating is most directly assessed by a magnetic pull-off gauge?

  1. Dry film thickness Correct answer.
  2. Adhesion strength
  3. Surface profile
  4. Wet film thickness

Explanation

Magnetic pull-off gauges measure the force needed to detach a magnet from a ferromagnetic substrate, which varies with the distance between magnet and steel, i.e., the coating thickness. They are a standard non-destructive method for dry film thickness on steel. Surface profile and adhesion are measured by different instruments.

Question 2Marine coatings inspection fundamentals

A coating inspector records a dry film thickness reading below the specified minimum. What is the most appropriate first action?

  1. Accept the area because average thickness meets specification
  2. Recoat only if visible rust appears
  3. Record the reading and take no action
  4. Reject the area and require additional coats to reach specification Correct answer.

Explanation

Specifications typically require both minimum and maximum thickness limits, and individual readings below the minimum are nonconforming regardless of the average. The area should be identified and corrective coating applied. Waiting for visible corrosion is not an inspection criterion.

Question 3Marine coatings inspection fundamentals

Which surface preparation standard designation refers to abrasive blast cleaning to a near-white finish?

  1. Sa 1
  2. Sa 2½ Correct answer.
  3. Sa 3
  4. Sa 2

Explanation

In the ISO 8501-1 visual standards, Sa 2½ denotes very thorough blast cleaning, commonly called near-white. Sa 3 is white metal, Sa 2 is thorough, and Sa 1 is light blast cleaning.

Question 4Marine coatings inspection fundamentals

An inspector observes a coating defect where the film has lifted from the substrate in large, brittle flakes with the topcoat intact. Which failure mode is most consistent with this appearance?

  1. Undercutting corrosion
  2. Intercoat delamination Correct answer.
  3. Solvent blistering
  4. Cissing

Explanation

Intercoat delamination appears as separation between coating layers, often with the upper film lifting in sheets. Blistering shows dome-shaped raised areas, cissing shows small circular voids, and undercutting corrosion originates at a break in the film.

Question 5Marine coatings inspection fundamentals

Which environmental condition most directly determines whether a coating can be applied without solvent entrapment?

  1. Ambient wind speed
  2. Substrate temperature relative to dew point Correct answer.
  3. Substrate thickness
  4. Coating color

Explanation

Substrate temperature must be above the dew point by a specified margin to prevent condensation on the surface, which can trap moisture and cause adhesion failure. Wind speed and thickness affect drying but not condensation directly.

Question 6Marine coatings inspection fundamentals

A wet film thickness gauge reads 200 µm on a coating with a specified volume solids of 60%. What is the approximate dry film thickness?

  1. 120 µm Correct answer.
  2. 80 µm
  3. 100 µm
  4. 160 µm

Explanation

Dry film thickness is calculated as wet film thickness multiplied by volume solids fraction: 200 µm × 0.60 = 120 µm. This relationship assumes no solvent retention beyond the stated volume solids.

Question 7Marine coatings inspection fundamentals

Which instrument is used to measure surface profile by pressing a tape onto the blasted surface and measuring the impression?

  1. Holiday detector
  2. Pull-off adhesion tester
  3. Replica tape Correct answer.
  4. Wet film comb

Explanation

Replica tape (press-o-film) is pressed onto the surface, and the compressed foam impression is measured with a micrometer to give a profile value. Wet film combs measure wet thickness, holiday detectors find discontinuities, and pull-off testers measure adhesion.

Question 8Marine coatings inspection fundamentals

An inspector finds that a high-build epoxy was applied over a surface with visible oil contamination. Which failure is most likely to result?

  1. Orange peel
  2. Chalking
  3. Poor adhesion Correct answer.
  4. Mudcracking

Explanation

Oil contamination prevents the coating from wetting and bonding to the substrate, leading to poor adhesion or delamination. Chalking is a surface degradation, orange peel is a surface texture, and mudcracking is a drying-related cracking pattern.

Question 9Marine coatings inspection fundamentals

Which of the following best describes the purpose of a holiday detector in coating inspection?

  1. To locate discontinuities in the coating film Correct answer.
  2. To assess the degree of cure
  3. To measure surface profile
  4. To measure coating thickness

Explanation

Holiday detectors apply a voltage across the coating and detect current flow through pinholes, voids, or thin spots, indicating discontinuities. Thickness and profile are measured with other instruments, and cure is assessed by solvent rub or similar tests.

Question 10Marine coatings inspection fundamentals

A specification requires a surface profile of 50 to 75 µm. An inspector measures 90 µm. What is the appropriate interpretation?

  1. Acceptable because higher profile improves adhesion
  2. Nonconforming because profile is below minimum
  3. Acceptable if the coating is thick enough
  4. Nonconforming because profile exceeds the maximum Correct answer.

Explanation

Profile specifications have both upper and lower limits. Excessive profile can cause peaks to protrude through the coating, leading to premature corrosion, so exceeding the maximum is nonconforming.

Question 11Marine coatings inspection fundamentals

Which of the following is a common cause of pinholes in a coating film?

  1. Solvent entrapment during rapid drying Correct answer.
  2. Excessive film thickness
  3. Substrate temperature above dew point
  4. Proper surface preparation

Explanation

Rapid solvent evaporation can leave pinholes as solvent escapes through the film. Excessive thickness may cause other defects, and proper conditions and preparation reduce defects rather than cause them.

Question 12Marine coatings inspection fundamentals

Which test method is commonly used to assess the degree of cure of a solvent-borne coating in the field?

  1. Wet film comb
  2. Solvent rub test Correct answer.
  3. Replica tape
  4. Pull-off adhesion test

Explanation

The solvent rub test uses a solvent-soaked cloth rubbed on the film; softening indicates incomplete cure. Pull-off tests measure adhesion, and the comb and tape measure thickness and profile.

Question 13Marine coatings inspection fundamentals

An inspector observes a coating with a fine, uniform powdery deposit on the surface after outdoor exposure. This is best described as:

  1. Cracking
  2. Flaking
  3. Chalking Correct answer.
  4. Blistering

Explanation

Chalking is the formation of a powdery layer on the coating surface as the binder degrades under UV exposure. Blistering, cracking, and flaking involve film separation or rupture rather than a powdery residue.

Question 14Marine coatings inspection fundamentals

A coating inspector is verifying that a stripe coat was applied to welds and edges. Why is this inspection point important?

  1. Stripe coats reduce drying time
  2. Stripe coats improve color uniformity
  3. Stripe coats ensure adequate coverage on difficult geometries Correct answer.
  4. Stripe coats increase volume solids

Explanation

Welds, edges, and corners are difficult to coat uniformly with spray, so a stripe coat ensures adequate film build and coverage in these areas. It does not primarily affect color, drying, or volume solids.

Question 15Marine coatings inspection fundamentals

Which of the following describes the correct procedure for measuring dew point in the field?

  1. Measure substrate temperature with an infrared gauge only
  2. Measure relative humidity only
  3. Estimate dew point from ambient temperature alone
  4. Use a sling psychrometer or electronic hygrometer to determine dew point from dry- and wet-bulb temperatures Correct answer.

Explanation

Dew point is determined from dry-bulb and wet-bulb temperatures using a psychrometric chart or an electronic hygrometer. Ambient temperature alone or humidity alone is insufficient to determine dew point.

Question 16Marine coatings inspection fundamentals

A coating defect appears as a series of parallel cracks following the direction of application. This is most likely:

  1. Undercutting
  2. Cissing
  3. Solvent blistering
  4. Mudcracking Correct answer.

Explanation

Mudcracking produces a pattern of cracks, often roughly parallel or polygonal, caused by high film thickness or rapid drying stresses. Cissing produces circular craters, blistering produces domes, and undercutting is corrosion-related.

Question 17Marine coatings inspection fundamentals

Which of the following is the primary reason for specifying a maximum dry film thickness?

  1. To reduce material cost
  2. To improve color match
  3. To increase adhesion
  4. To prevent defects such as cracking and solvent entrapment Correct answer.

Explanation

Excessive film thickness can cause solvent entrapment, mudcracking, and internal stress, so maximum limits protect coating integrity. Cost and color are secondary considerations.

Question 18Marine coatings inspection fundamentals

A pull-off adhesion test yields a result where the coating separates from the substrate at a low stress value. This indicates:

  1. Substrate failure
  2. Good adhesion
  3. Adhesive failure at the coating-substrate interface Correct answer.
  4. Cohesive failure within the coating

Explanation

Failure at the coating-substrate interface is adhesive failure and indicates poor bonding. Cohesive failure occurs within the coating or substrate, not at the interface.

Question 19Marine coatings inspection fundamentals

Which surface preparation method is typically required before applying a zinc-rich primer to steel?

  1. Abrasive blast cleaning to a specified standard Correct answer.
  2. Power tool cleaning to bare metal
  3. Solvent wiping only
  4. Hand tool cleaning

Explanation

Zinc-rich primers require a clean, profiled surface, typically achieved by abrasive blast cleaning to a specified standard such as Sa 2½. Solvent wiping, power tool, and hand tool cleaning do not provide the required profile and cleanliness.

Question 20Marine coatings inspection fundamentals

An inspector finds that relative humidity is 85% and the substrate temperature is 3°C above the dew point. The specification requires a minimum of 3°C above dew point and maximum 85% RH. What is the appropriate action?

  1. Stop work because RH exceeds the limit
  2. Proceed only if the coating is solvent-free
  3. Stop work because substrate temperature is below dew point
  4. Proceed because both criteria are met Correct answer.

Explanation

The readings meet both stated criteria: the substrate is at least 3°C above dew point and RH does not exceed 85%. Work may proceed under these conditions.

Question 21Marine coatings inspection fundamentals

Which of the following best describes the role of a holding primer?

  1. To protect a prepared surface temporarily before the full coating system is applied Correct answer.
  2. To improve color match
  3. To increase surface profile
  4. To provide long-term corrosion protection

Explanation

Holding primers are thin, temporary coatings applied to preserve a prepared surface until the full system can be applied. They are not intended for long-term protection.

Question 22Marine coatings inspection fundamentals

A coating inspector observes rust staining bleeding through a coating film in localized spots. Which inspection finding is most likely?

  1. Incomplete cure
  2. Corrosion initiating at a coating discontinuity Correct answer.
  3. Excessive film thickness
  4. Mechanical damage to the film

Explanation

Localized rust staining often indicates corrosion starting at a pinhole, crack, or thin spot where the barrier is compromised. Mechanical damage and incomplete cure can contribute but the direct finding is a discontinuity.

Question 23Marine coatings inspection fundamentals

Which of the following is the correct interpretation of a wet film thickness reading taken immediately after application?

  1. It measures surface profile
  2. It provides an early indication of whether dry film thickness will meet specification Correct answer.
  3. It confirms final dry film thickness
  4. It measures adhesion

Explanation

Wet film thickness multiplied by volume solids gives an estimated dry film thickness, allowing early correction before the coating dries. It does not confirm final DFT, profile, or adhesion.

Question 24Marine coatings inspection fundamentals

A coating system shows blistering that contains liquid when ruptured. Which condition is most likely responsible?

  1. Osmotic blistering from soluble salts on the substrate Correct answer.
  2. Abrasive contamination from blast media
  3. Excessive surface profile
  4. Improper stripe coating

Explanation

Osmotic blistering occurs when soluble salts or contaminants on the substrate draw moisture through the film, forming liquid-filled blisters. Abrasive contamination and profile issues cause different defects.

Question 25Marine coatings inspection fundamentals

Which of the following best describes the purpose of a pre-job conference in coating inspection?

  1. To align all parties on specification requirements, inspection points, and hold points before work begins Correct answer.
  2. To measure surface profile
  3. To finalize the coating color selection
  4. To conduct the final acceptance inspection

Explanation

A pre-job conference aligns the owner, contractor, and inspector on specification requirements, inspection points, and hold points before work starts, reducing disputes. It is not a measurement or final acceptance activity.

Question 26Marine coatings inspection fundamentals

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

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

Explanation

A magnetic pull-off gauge measures the force required to pull a magnet from the coated steel, which correlates to coating thickness. Wet film combs measure wet coatings, comparators assess surface profile, and holiday detectors find discontinuities.

Question 27Marine coatings inspection fundamentals

What does a reading of 100% relative humidity indicate?

  1. The air is saturated with water vapor Correct answer.
  2. The substrate is too warm for coating
  3. The air temperature equals the dew point
  4. The coating will cure faster

Explanation

Relative humidity is the ratio of actual water vapor pressure to the saturation vapor pressure at a given temperature. At 100% RH, the air holds the maximum water vapor possible at that temperature, so it is saturated.

Question 28Marine coatings inspection fundamentals

Which of the following is a primary purpose of a stripe coat?

  1. To fill pits and surface imperfections
  2. To improve the adhesion of the primer to the substrate
  3. To increase the overall thickness of the main coating
  4. To provide extra protection at edges, welds, and corners Correct answer.

Explanation

A stripe coat is an additional coat applied to areas that are difficult to coat uniformly, such as edges, welds, and corners, to ensure adequate coverage and protection. It is not intended to increase overall thickness or fill pits.

Question 29Marine coatings inspection fundamentals

What is the main consequence of applying a coating when the substrate temperature is below the dew point?

  1. The surface profile will be reduced
  2. Moisture will condense on the surface, leading to poor adhesion Correct answer.
  3. The coating will cure too rapidly
  4. The coating will become too viscous to apply

Explanation

When the substrate temperature is at or below the dew point, moisture from the air condenses on the surface. This moisture interferes with coating adhesion and can cause defects such as blistering or delamination.

Question 30Marine coatings inspection fundamentals

Which of the following best describes the role of a pre-job conference in coating inspection?

  1. To establish communication and clarify specifications among all parties Correct answer.
  2. To apply the first coat of paint
  3. To conduct destructive testing of the coating
  4. To perform final acceptance of the coating job

Explanation

A pre-job conference brings together the owner, contractor, inspector, and other stakeholders to review specifications, responsibilities, and communication procedures before work begins. It helps prevent misunderstandings and ensures everyone is aligned.

Question 31Marine coatings inspection fundamentals

Which of the following is a common method for measuring surface profile?

  1. Surface comparator Correct answer.
  2. Pull-off adhesion tester
  3. Wet film comb
  4. Holiday detector

Explanation

A surface comparator consists of reference discs or plates with known profile depths that are visually compared to the blasted surface. It is a common field method for assessing surface roughness.

Question 32Marine coatings inspection fundamentals

What does a blister in a coating film typically indicate?

  1. Improper surface profile
  2. Insufficient curing agent
  3. Poor adhesion due to moisture or contamination Correct answer.
  4. Excessive film thickness

Explanation

Blistering often results from moisture or contamination trapped beneath the coating or within the film, causing localized loss of adhesion and lifting of the coating. It can also be caused by solvent entrapment, but moisture is a common cause.

Question 33Marine coatings inspection fundamentals

Which of the following is the correct action if a coating inspector finds that the surface preparation does not meet the specified standard?

  1. Increase the coating thickness to compensate
  2. Apply a primer to cover the surface
  3. Proceed with coating application to avoid delays
  4. Document the finding and request rework Correct answer.

Explanation

The inspector's role is to verify conformance to specifications. If surface preparation is inadequate, the inspector should document the nonconformance and require the contractor to rework the surface before coating.

Question 34Marine coatings inspection fundamentals

Which of the following is a primary reason for specifying a maximum dry film thickness?

  1. To ensure adequate coverage of the substrate
  2. To reduce the cost of coating materials
  3. To improve the appearance of the coating
  4. To prevent solvent entrapment and mud cracking Correct answer.

Explanation

Excessive dry film thickness can lead to solvent entrapment, mud cracking, and poor adhesion due to internal stresses. Specifying a maximum helps avoid these defects.

Question 35Marine coatings inspection fundamentals

An inspector measures a surface profile of 25 µm on a substrate that was specified to have a 50-75 µm profile. What is the most appropriate interpretation?

  1. The profile is acceptable if the coating is thick enough
  2. The profile is too high and may cause shadowing
  3. The profile is too low and may not provide adequate adhesion Correct answer.
  4. The profile is within the specified range

Explanation

The specified range is 50-75 µm, so a reading of 25 µm is below the minimum. Insufficient profile can reduce the mechanical adhesion of the coating.

Question 36Marine coatings inspection fundamentals

Which of the following is the most likely cause of pinholes in a coating film?

  1. Too high an application temperature
  2. Excessive surface profile
  3. Insufficient curing agent
  4. Solvent entrapment during application Correct answer.

Explanation

Pinholes often result from solvent or air trapped in the film as it cures, creating small holes as they escape. They can also be caused by application over a porous surface, but solvent entrapment is a common cause.

Question 37Marine coatings inspection fundamentals

A coating inspector observes rust staining bleeding through a coating film in localized spots. Which inspection finding should be investigated?

  1. Insufficient surface profile
  2. Contamination or iron particles on the surface before coating Correct answer.
  3. Excessive coating thickness
  4. Improper curing agent ratio

Explanation

Rust staining through a coating often indicates that iron particles or contamination were present on the surface before coating, leading to localized corrosion. It can also indicate mechanical damage, but contamination is a common cause.

Question 38Marine coatings inspection fundamentals

An inspector is reviewing a coating specification that requires a minimum DFT of 250 µm. After application, readings show 230, 240, 260, and 270 µm. What is the appropriate action?

  1. Accept the coating because the average is above 250 µm
  2. Reject the coating because some readings are below minimum Correct answer.
  3. Apply an additional coat to bring all readings above 250 µm
  4. Re-measure with a different gauge

Explanation

Specifications typically require that all readings meet or exceed the minimum DFT. Since some readings are below 250 µm, the coating does not meet the specification and should be rejected or remedied.

Question 39Marine coatings inspection fundamentals

Which of the following best explains why a zinc-rich primer provides corrosion protection to steel?

  1. It provides sacrificial cathodic protection Correct answer.
  2. It acts as a barrier to moisture and oxygen
  3. It inhibits corrosion by releasing inhibitors
  4. It passivates the steel surface

Explanation

Zinc-rich primers protect steel by acting as a sacrificial anode; the zinc corrodes preferentially to protect the steel. This is cathodic protection.

Question 40Marine coatings inspection fundamentals

An inspector notices that a coating has a mottled appearance with patches of different gloss. Which factor is most likely responsible?

  1. Uneven application or varying film thickness Correct answer.
  2. Improper curing agent mixing
  3. Contamination of the substrate
  4. Inconsistent surface profile

Explanation

Mottled appearance or patches of different gloss often result from uneven application or varying film thickness, leading to differences in surface finish. Other factors like contamination can cause defects but not typically gloss variation.

Question 41Marine coatings inspection fundamentals

During inspection of an abrasive-blasted steel surface, the inspector must confirm the surface cleanliness grade. Which visual standard defines the grade where all visible oil, grease, dirt, and mill scale are removed and any remaining residue appears as light shadows or streaks?

  1. Sa 2½ Correct answer.
  2. Sa 2
  3. Sa 1
  4. Sa 3

Explanation

The blast-cleaning grades progress from Sa 1 (light blast) through Sa 2 (thorough blast) and Sa 2½ (very thorough blast) to Sa 3 (white metal). Sa 2½ permits only light shadows or streaks of staining and is the grade most commonly specified for immersion service. Sa 3 requires a uniformly grey-white surface with no residue at all.

Question 42Marine coatings inspection fundamentals

An inspector measures ambient conditions and records an air temperature of 20 °C, a steel surface temperature of 18 °C, and a dew point of 16 °C. What is the correct interpretation of these readings?

  1. Conditions are unacceptable because the air is warmer than the steel
  2. Conditions are acceptable because the air temperature is above the surface temperature
  3. Conditions are acceptable because the surface is above the dew point
  4. Conditions are unacceptable because the surface is only 2 °C above the dew point Correct answer.

Explanation

A widely applied rule requires the steel temperature to be at least 3 °C above the dew point before coating is applied. Here the margin is only 2 °C, so the risk of condensation on the surface is too high for application to proceed. The relative values of air and steel temperature do not by themselves determine acceptability.

Question 43Marine coatings inspection fundamentals

A pull-off adhesion test is performed and the coating separates cleanly from the steel with essentially no coating remaining on the substrate. How should this result be classified?

  1. Adhesive failure at the substrate interface Correct answer.
  2. Adhesive failure between coats
  3. A valid result that requires no further comment
  4. Cohesive failure within the coating film

Explanation

Failure is described by where the separation occurs. When the coating detaches from the substrate and leaves the steel essentially bare, the break is adhesive at the substrate interface. Cohesive failure instead leaves coating on both faces of the break because the film itself ruptured.

Question 44Marine coatings inspection fundamentals

An inspector suspects that a coating has been applied over a surface that was not adequately cleaned, and wants a field test to detect soluble salt contamination on the prepared steel. Which method is appropriate for this purpose?

  1. Tooke gauge profile measurement
  2. Wet sponge low-voltage holiday test
  3. Magnetic pull-off DFT gauge
  4. Bresle patch sampling with conductivity measurement Correct answer.

Explanation

Soluble salts are detected by extracting contamination from a defined area and measuring the conductivity of the resulting solution. The Bresle patch method is the standard field technique for this, with results expressed as surface density of salt. The other listed instruments measure profile, thickness, or film continuity, none of which quantifies ionic contamination.

Question 45Marine coatings inspection fundamentals

A high-build epoxy is applied to a vertical steel surface and the inspector observes sagging in several areas. Which application factor is the most direct cause of this defect?

  1. Insufficient surface profile
  2. Contamination of the substrate by oil
  3. Excessive film thickness per pass Correct answer.
  4. Too long a recoat interval

Explanation

Sagging occurs when too much wet material is deposited in one pass, so gravity overcomes the coating's viscosity before it cures. Reducing wet film thickness per coat or adjusting thixotropy addresses the cause. Profile, recoat interval, and oil contamination produce different defects such as poor adhesion or intercoat problems.

Question 46Marine coatings inspection fundamentals

An inspector is asked to verify that a blast-cleaned surface has an adequate angular profile before primer application. Which instrument is designed specifically to assess surface profile?

  1. Dial thickness gauge pressed onto the coating
  2. Wet film comb
  3. Replica tape read with a spring micrometer Correct answer.
  4. Holiday detector

Explanation

Replica tape is pressed onto the prepared surface so the profile is captured in the tape, and the tape is then read with a spring micrometer to give a profile value. This is a recognised field method for quantifying anchor pattern. Wet film combs, coating gauges, and holiday detectors measure other properties entirely.

Question 47Marine coatings inspection fundamentals

An inspector takes a set of dry film thickness readings on a coated steel structure and finds that individual readings vary widely, though the average meets specification. What is the most appropriate basis for judging compliance?

  1. Reject the coating because any variation is unacceptable
  2. Accept the coating because the average satisfies the specification
  3. Accept the coating if the lowest single reading exceeds the minimum by any margin
  4. Compare individual readings against the specified minimum and maximum limits, not only the average Correct answer.

Explanation

Most coating specifications set both a minimum and a maximum DFT and apply limits to individual readings as well as to the average. A compliant average can hide low spots that risk early corrosion and high spots that risk cracking or solvent entrapment. Judging against the stated individual limits is the correct approach.

Question 48Marine coatings inspection fundamentals

A two-component epoxy topcoat is being applied, and the inspector notes that the mixed product has been standing in the pot well beyond the time stated on the product data sheet. What is the most likely consequence if it is applied?

  1. Improved flow and levelling of the finish
  2. Increased film build with no change in properties
  3. Reduced curing and possible loss of film integrity Correct answer.
  4. Higher gloss with no effect on performance

Explanation

The pot life defines the working time after mixing during which the product retains usable properties. Beyond pot life the reaction has advanced, so viscosity rises and the applied film may not cure correctly, compromising adhesion and integrity. The other outcomes describe benefits that do not follow from using expired material.

Question 49Marine coatings inspection fundamentals

An inspector is reviewing a coating specification for a ballast tank and notes a requirement for a stripe coat on weld seams, cut edges, and areas of complex geometry. What is the technical basis for this requirement?

  1. It compensates for low dry film thickness that tends to occur at edges and welds Correct answer.
  2. It replaces the need for the main coat in those areas
  3. It removes the need for surface preparation at those locations
  4. It provides a visual marker for the applicator

Explanation

Spray application tends to deposit less material on sharp edges and irregular geometry, so those areas are prone to thin films and early breakdown. A stripe coat builds additional thickness over these features before or after the main coat. It supplements rather than replaces the main coat or the surface preparation.

Question 50Marine coatings inspection fundamentals

An inspector finds a series of small, crater-like depressions in a freshly applied coating that expose the primer beneath. Which condition is the most likely explanation?

  1. Insufficient wet film thickness across the whole area
  2. Excessive surface profile under the coating
  3. Cissing caused by surface contamination such as oil or silicone Correct answer.
  4. Solvent entrapment beneath a fully cured film

Explanation

Cissing or cratering occurs when the wet coating cannot wet the substrate evenly because of local contamination with low surface energy material such as oil, grease, or silicone. The film pulls away from the contaminated spots, leaving craters. Solvent entrapment produces blisters or pinholes after cure, and profile or film thickness issues do not create isolated craters.