AMPP PCS key terms

The roughness of a prepared steel surface, measured as the average peak-to-valley depth created by abrasive blasting. It helps coating adhesion by giving the film a mechanical grip on the substrate.

All work done to clean and roughen a substrate before coating, including removing rust, mill scale, oil, and salts. It is the single largest factor in coating performance and service life.

A surface preparation method that propels grit, shot, or other media at high velocity to remove rust, scale, and old coatings and to create a profile. It is the standard method for achieving near-white finishes.

A published visual reference, such as the NACE/SSPC joint standards, that defines how much mill scale, rust, and residue may remain after blast cleaning. It lets an inspector judge acceptance consistently.

A set of photographic or physical reference plates used to compare a prepared surface against a specified cleanliness or profile grade. Inspectors use them to make consistent, repeatable judgments.

Soluble chloride, sulfate, or other salts left on a surface after cleaning, often invisible. They draw moisture through the coating and cause blistering, undercutting, and premature failure, so they are tested before coating.

A field method that measures the electrical conductivity of water used to wash a surface, indicating soluble salt levels. Results are compared against a specified maximum before coating is applied.

The temperature at which air becomes saturated and moisture condenses on a surface. Coating should not be applied when the substrate is at or near dew point, because condensation ruins adhesion.

The temperature of the substrate being coated, which governs cure, viscosity, and moisture condensation risk. It is measured directly and compared with dew point and the product's application limits.

The amount of water vapor in the air expressed as a percentage of the maximum it can hold at that temperature. High humidity slows solvent and water evaporation and can affect cure and adhesion.

The thickness of a coating measured immediately after application while still wet. It is checked with a comb or wheel gauge to confirm the applicator is on target before the film dries.

The thickness of the cured coating, measured with magnetic or eddy-current gauges. It is compared against the specified range because both thin and thick films can cause premature failure.

An instrument that measures dry coating thickness on steel by sensing the pull of a magnet or magnetic flux change. It is the standard field tool for verifying DFT on ferrous substrates.

A non-destructive instrument that measures coating thickness on non-ferrous metals by detecting changes in an induced electromagnetic field. It is used on aluminum and other conductive substrates.

A unit of thickness equal to one thousandth of an inch, commonly used to express coating thickness in the United States. Specifications often state DFT ranges in mils or in micrometers.

A small discontinuity, pinhole, or thin spot in a coating that exposes or nearly exposes the substrate. Holidays are located with a high-voltage or low-voltage detector and must be repaired.

A device that passes a voltage across a coated surface to reveal breaks in the film, indicated by a spark or alarm. High-voltage units suit thick films; low-voltage units suit thin films.

A tiny hole through a coating film, often caused by solvent escape, air entrapment, or surface contamination. It creates a path for moisture and corrosion and is found by holiday testing.

A field or lab method that measures how strongly a coating bonds to the substrate or to a previous coat. Common methods include pull-off and cross-cut tape tests.

An adhesion test in which a dolly is glued to the coating and pulled perpendicular to the surface until failure. The load and failure mode are recorded to judge bond strength.

An adhesion test in which a lattice of cuts is made through the film and tape is applied and removed. The amount of coating lifted is compared with a reference chart to grade adhesion.

A two-component thermosetting coating formed by reacting an epoxy resin with a curing agent. It provides excellent adhesion and chemical resistance but chalks and yellows in sunlight, so it is often topcoated.

A coating based on polyurethane resin, typically used as a topcoat for its color and gloss retention and UV resistance. It is commonly applied over epoxy in a multi-coat system.

A primer containing a high percentage of zinc dust that protects steel sacrificially, similar to galvanizing. It is used in aggressive environments and often requires a mist coat to avoid bubbling.

A coating, such as a zinc-rich primer, that corrodes preferentially to protect the underlying steel. It provides galvanic protection at scratches and damaged areas.

Corrosion caused when two dissimilar metals are joined in an electrolyte, with the more active metal corroding. Coating selection and isolation help prevent it at connections and fasteners.

A coating supplied as two parts, a base and a curing agent, that must be mixed in the correct ratio before use. Mixing errors, wrong induction time, or exceeded pot life ruin performance.

The usable working time after a two-component coating is mixed, before it thickens or gels. Material used past pot life may not cure properly or may lose adhesion.

The waiting period after mixing a two-component coating and before application, allowing the chemical reaction to begin. Skipping or shortening it can cause defects such as pinholing or poor cure.

A greasy or waxy surface film that forms on some epoxy coatings when amines react with moisture and carbon dioxide during cure. It must be removed before the next coat or adhesion will fail.

The time range after application during which the next coat can be applied and still bond properly. Coating outside this window may require abrading or solvent wiping to restore adhesion.

The final coat of a coating system, chosen for appearance, weather resistance, and chemical exposure. It sits over primer and intermediate coats and is often a polyurethane.

The first coat applied to a prepared substrate, formulated for adhesion and corrosion protection. It anchors the coating system and is often zinc-rich or epoxy-based on steel.

The complete set of coats, primer through topcoat, specified for a given service environment. Each layer has a defined thickness and function, and the system is judged as a whole.

Loss of coating adhesion around a deliberate defect on cathodically protected steel, driven by electrochemical reactions at the exposed metal. It is tested in the lab to predict buried or immersed service performance.

A written record of conditions, measurements, and observations made during each inspection shift. It documents ambient conditions, surface prep, thickness readings, and nonconformances for the project file.

A stage in the coating process where work must stop until the inspector verifies and approves it. It prevents covering up unacceptable work and is defined in the inspection and test plan.

A project document listing the inspections, tests, acceptance criteria, and hold points for each stage of coating work. It guides the inspector and defines who signs off at each step.

A documented failure to meet a specification requirement, such as low thickness or poor surface prep. It triggers a disposition such as rework, repair, or acceptance by concession.