AMPP CCAS key terms

A surface preparation method that propels abrasive particles at high velocity against a substrate to remove rust, mill scale, old coatings, and contaminants, while creating a roughened profile that helps the coating bond.

The microscopic roughness created on a substrate by abrasive blasting or other mechanical preparation; it increases surface area and provides mechanical keying so the coating can adhere strongly.

A thin, brittle oxide layer formed on steel during hot rolling. It must be removed before coating because it can crack, disbond, and trap moisture, leading to premature coating failure.

Chlorides, sulfates, and other water-soluble salts left on a surface after preparation. They attract moisture, promote osmotic blistering, and cause coating disbondment, so they must be measured and removed before application.

The temperature at which moisture in the air begins to condense on a surface. Coating work usually requires the substrate temperature to be at least 3°C (5°F) above dew point.

The highest abrasive blast cleaning standard: all visible rust, mill scale, coatings, and foreign matter are removed, leaving a uniform gray-white surface with a profile suitable for demanding coating systems.

A blast cleaning standard in which all visible rust, mill scale, coatings, and foreign matter are removed except for very light shadows, streaks, or stains that do not affect coating performance.

A blast cleaning standard that removes all visible rust, mill scale, coatings, and foreign matter, but permits staining and slight shadows over no more than about one-third of the surface.

A light blast cleaning standard that removes loose rust, loose mill scale, loose coatings, and loose foreign matter, while tightly adherent material may remain. It is used where only light cleaning is needed.

A surface preparation method that uses high-pressure water, sometimes with abrasives, to remove coatings, rust, salts, and debris. Its cleaning level depends on pressure and is often described by SSPC water-jetting standards.

A thin protective coating applied to prepared steel, often shortly after blasting, to prevent rusting during fabrication or before the full coating system is applied. It must be compatible with later coats.

The film-forming component of a coating that holds pigment particles together and bonds the coating to the substrate. The binder type largely determines the coating's chemical resistance, adhesion, flexibility, and curing behavior.

Solid particles dispersed in a coating that provide color, opacity, and corrosion resistance, and can influence film strength, gloss, and weathering. Examples include titanium dioxide, zinc dust, and micaceous iron oxide.

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

Any organic chemical that evaporates readily at room temperature and can contribute to air pollution. Coating regulations limit VOC content, so formulators use waterborne, high-solids, or solvent-free products to comply.

A thermoset coating formed by reacting an epoxy resin with a curing agent. It offers excellent adhesion and chemical resistance but can chalk and lose gloss when exposed to sunlight, so it is often topcoated.

A primer containing a high percentage of zinc dust that protects steel primarily by galvanic action. It is often used as the first coat in demanding atmospheric or immersion coating systems.

A coating based on polyurethane resin, commonly used as a finish coat because it resists weathering, retains gloss, and provides good chemical and abrasion resistance. It is often applied over an epoxy intermediate coat.

The usable working time after a two-component coating's components are mixed, during which the product can still be applied properly. After pot life expires, viscosity rises and the coating may not cure or perform correctly.

A waiting period after mixing two-component coatings, before application, that allows chemical components to react and the mixture to become uniform. The product data sheet specifies whether induction time is required and for how long.

The chemical or physical process by which a coating changes from a liquid film into a solid, adherent film with its intended properties. Cure may involve solvent evaporation, chemical reaction, or both, and is affected by temperature and humidity.

The thickness of a coating immediately after application while it is still wet. Measuring WFT during application helps the applicator adjust spray passes or film build to achieve the required dry film thickness.

The thickness of the cured coating measured after the film has dried or cured. DFT is a key acceptance criterion because too little film may fail prematurely, while too much can cause cracking or poor adhesion.

A spray method that forces coating through a small orifice at high hydraulic pressure, atomizing it without compressed air. It gives high film build and transfer efficiency but requires careful pressure, tip, and distance control.

Spray equipment that meters and mixes two or more coating components at the gun, usually for fast-curing or short-pot-life materials. Correct ratio, mixing, and flushing are critical to avoid off-ratio or partially cured coatings.

The width of the coating pattern produced by a spray gun at a given distance. Selecting the right fan width helps maintain overlap, uniform film build, and efficient coverage without excessive overspray.

A first coat brushed or sprayed along edges, welds, corners, bolts, and other hard-to-coat areas before general spraying. It ensures adequate film thickness where spray coverage tends to be thinner.

A discontinuity, pinhole, crack, or thin spot in a coating that exposes the substrate or allows electrical current to pass through. Holidays are located with a holiday detector and must be repaired.

An inspection instrument that applies a voltage across a coating to find breaks, pinholes, or thin areas. Low-voltage units are used for thin films, while high-voltage units are used for thicker protective coatings.

A destructive test in which a loading fixture is bonded to the coating and pulled perpendicularly until the coating detaches. The failure stress and failure mode help evaluate adhesion and coating integrity.

A surface defect with a dimpled, citrus-like texture caused by poor flow or leveling of the wet coating. It can result from incorrect viscosity, too little solvent, excessive film thickness, or poor spray atomization.

A defect in which wet coating flows downward under gravity, forming thick curtains or tear-shaped drips. It is caused by excessive film thickness, too much solvent, poor application technique, or inadequate surface preparation.

A greasy or waxy film on the surface of an amine-cured epoxy, caused by reaction of the curing agent with moisture and carbon dioxide. It can prevent adhesion of subsequent coats if not removed.

A coating defect appearing as small, circular craters or voids where the coating pulls away from the substrate. It is usually caused by oil, grease, silicone, or other surface contamination that lowers surface energy.

A defect with small blisters or pinholes caused by solvent vapor escaping from a coating that skins over or cures too quickly. Thick films, hot conditions, or short flash-off times increase the risk.

A standardized document that provides information about a chemical product's hazards, safe handling, PPE, first aid, storage, and emergency response. Applicators must review the SDS before using a coating or cleaning product.

A respirator that delivers clean breathing air from a remote source through a hose to a facepiece or hood. It is used when coatings, solvents, or blasting dust create hazards that air-purifying respirators cannot safely handle.

An enclosed or partially enclosed area with limited entry and exit, not designed for continuous occupancy, and potentially hazardous due to toxic air, oxygen deficiency, or flammable gases. Entry usually requires permits, testing, and attendants.

The lowest concentration of a flammable vapor or gas in air that can ignite when exposed to an ignition source. Gas meters use percent LEL to warn workers before an atmosphere becomes explosive.

A serious injury caused when a high-pressure airless spray gun injects coating or solvent through the skin. The wound may look minor, but the material can cause deep tissue damage, infection, and necrosis, requiring immediate medical care.