AMPP Marine Coatings key terms

The microscopic roughness created on a substrate by abrasive blasting or power tools, measured as peak-to-valley height. It gives the coating a mechanical key to grip, improving adhesion and resistance to undercutting at damage sites.

A reference plate or disc with graded roughness patches used to visually and tactilely estimate anchor profile by comparison. The prepared surface is matched against known patches, giving an approximate profile reading in the field.

A surface preparation method that propels grit, slag, or shot at high velocity to remove rust, mill scale, and old coatings while creating a profile. It is the most common preparation method for high-performance marine coating systems.

The blasting medium, such as garnet, coal slag, or steel shot, used to clean and profile a surface. Its type, size, shape, and cleanliness affect productivity, profile depth, and the risk of contamination embedded in the steel.

A standardized description of how thoroughly a substrate has been cleaned, such as white metal, near-white, or commercial blast cleaning. The grade specifies remaining staining, rust, and residue permitted before coating application.

The oxide layer formed on steel during hot rolling. It is dense, brittle, and cathodic to steel, so it must be removed before coating; if left, it can flake and cause premature coating failure.

Light, thin rust that forms rapidly on a freshly blasted steel surface exposed to humid air. It must be removed or assessed against the coating specification before application, since it can impair adhesion.

Salt residue left on a surface from seawater, atmosphere, or blasting water. Chlorides promote osmotic blistering and corrosion under coatings, so soluble salt levels are tested and limited before painting.

A field or laboratory method that extracts and measures conductive salts, mainly chlorides, from a prepared surface. Results are compared with a specification limit to decide whether cleaning or re-blasting is required.

A measure of a liquid's ability to carry electrical current, used to quantify dissolved salts in a test solution. In salt testing, higher conductivity indicates more extracted ionic contamination from the surface.

The temperature at which air must be cooled for water vapor to condense. Coating work is normally prohibited when the steel surface temperature is at or near dew point, because condensation ruins adhesion.

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 or water evaporation and raises condensation risk during application and curing.

The temperature of the substrate itself, which governs coating viscosity, wetting, and cure. It is measured directly, not inferred from air temperature, and is compared with dew point and product limits.

The surrounding air temperature, humidity, and ventilation at the work site. They are recorded before and during application because they influence pot life, drying, and the risk of surface condensation.

The bond between a coating and the substrate or between successive coats. Good adhesion depends on clean, profiled substrate and proper application, and is verified by pull-off or similar tests.

A quantitative adhesion test in which a loading fixture is bonded to the coating and pulled normal to the surface until failure. The failure stress and failure mode indicate coating bond quality.

An inspection method that damages or removes coating, such as pull-off adhesion or coating removal for thickness checks. Damaged areas must be repaired to the specified system after testing.

The thickness of the cured coating film, measured with magnetic or eddy-current gauges. It is compared with the specified range, since too little thickness reduces protection and too much can cause cracking.

The thickness of a coating immediately after application, measured with a comb or wheel gauge. It is used to estimate eventual dry thickness and to catch application errors before the film cures.

An instrument, usually magnetic or electromagnetic, that measures dry coating thickness on steel or other substrates. Readings are taken at defined points and averaged against the specification.

Checking and adjusting an inspection instrument against a known reference so its readings are trustworthy. Gauges, thermometers, and test kits are calibrated at defined intervals and after damage or suspicion of error.

A discontinuity or pinhole in a coating film that exposes the substrate or a lower coat. Holidays are located with a high-voltage or low-voltage detector and must be repaired.

A tiny hole through a coating film, often caused by solvent escape, air entrapment, or application defects. Pinholes breach barrier protection and are detected by holiday testing.

A high-voltage holiday detection method in which a charged probe passes over the coating; a spark to the substrate signals a discontinuity. It is used on thicker films and requires careful voltage selection.

The percentage of a coating's liquid volume that remains as dry film after curing. It is used to calculate the wet film thickness needed to achieve a target dry thickness.

The working time after a two-component coating is mixed during which it remains usable. Exceeding pot life causes viscosity rise and poor cure, so mixed material must be discarded on schedule.

The waiting period after mixing some two-component coatings before application, allowing chemical reaction to begin. Skipping or extending it can cause application defects or incomplete cure.

A coating supplied as a base and a hardener that must be mixed in the correct ratio to cure. Accurate measurement and thorough mixing are essential for consistent film properties.

The chemical and physical process by which a coating converts from a liquid film to a solid, protective layer. Cure rate depends on temperature, humidity, film thickness, and product chemistry.

The minimum and maximum time allowed between applying successive coats. Too short risks solvent entrapment or lifting; too long can require surface roughening for adhesion.

Dirt, oil, grease, or amine blush present between coats that prevents proper bonding. It is removed by cleaning or light abrasion before the next coat is applied.

A waxy surface film that can form on epoxy coatings in cool, damp conditions as amine hardener reacts with moisture. It must be removed before overcoating to ensure adhesion.

Blister formation caused by water passing through a coating and accumulating at soluble salts or voids at the interface. It is a common marine failure linked to chloride contamination and poor surface preparation.

A method of preventing steel corrosion by making it the cathode of an electrochemical cell, using sacrificial anodes or impressed current. Coating and cathodic protection are designed together on immersed structures.

Corrosion accelerated when two dissimilar metals are electrically connected in an electrolyte, with the less noble metal corroding. Marine structures often require isolation or coating to limit this effect.

A localized electrochemical circuit formed by an anode, cathode, electrolyte, and metallic path. Understanding it explains why coatings must block electrolyte contact and why defects concentrate attack.

A document defining the required surface preparation, coating products, thicknesses, application conditions, and inspection acceptance criteria for a job. Inspectors compare actual work against it.

A project document listing inspection activities, hold points, methods, and acceptance criteria for coating work. It coordinates the inspector, applicator, and client so required checks are not missed.

A stage in the work where further progress is prohibited until a specified inspection is completed and accepted. Hold points are defined in the inspection plan and protect critical preparation or coating steps.