Coating Industry Glossary: 60+ Essential Terms Explained

Electrostatic Spray: The most common method of applying powder coating, in which powder particles are given an electrical charge and sprayed toward a grounded metal workpiece. The electrostatic attraction causes the powder to adhere uniformly to the part surface before curing.

Corona Charging: A method of electrostatically charging powder particles by passing them through a high-voltage electric field generated at the tip of the spray gun electrode. Corona charging is the most widely used charging method, offering high transfer efficiency and consistent film builds on most part geometries.

Application Terms

Tribo Charging: An alternative electrostatic charging method in which powder particles acquire their charge through friction as they pass through a PTFE-lined tube inside the spray gun. Tribo charging produces a softer, more uniform charge that is particularly effective for coating complex shapes and Faraday cage areas where corona guns struggle.

Fluidized Bed: An application method in which a preheated part is dipped into a tank of powder that is kept in a fluid-like state by a stream of air passing through a porous membrane at the base. The heat of the part melts the powder on contact, building a thick coating. Fluidized bed coating is used for heavy-duty applications requiring film thicknesses of 200-500 microns.

Transfer Efficiency: The percentage of sprayed powder that actually adheres to the workpiece, expressed as a ratio of powder deposited to powder sprayed. Modern electrostatic powder coating systems achieve first-pass transfer efficiencies of 60-80%, and with powder recovery and recycling, overall material utilization reaches 95-98%.

Faraday Cage Effect: A phenomenon in electrostatic spraying where electrical field lines concentrate on the outer edges and corners of a part, leaving recessed areas, internal corners, and channels with insufficient powder coverage. The effect is named after the physics principle and is managed through gun settings, part orientation, and tribo charging technology.

Film Thickness: The measured thickness of the cured powder coating film, typically expressed in microns. Architectural powder coatings are usually specified at 60-120 microns for a single coat. Film thickness is measured using magnetic or eddy current gauges and is a critical quality control parameter.

Overspray: Powder particles that do not adhere to the workpiece during spraying and are carried past the part by the air stream. In powder coating, overspray is collected by the recovery system, sieved to remove contaminants, and returned to the feed hopper for reuse, contributing to the high material utilization rates of the process.

Chemistry Terms

Thermoset: A type of polymer that undergoes an irreversible chemical cross-linking reaction during curing, forming a permanent three-dimensional molecular network. Most powder coatings are thermoset, meaning once cured they cannot be re-melted or reshaped. This cross-linked structure provides excellent chemical resistance, hardness, and durability.

Thermoplastic: A type of polymer that softens when heated and hardens when cooled, without undergoing chemical change. Thermoplastic powder coatings such as nylon, polyethylene, and PVC can be re-melted after application. They are used for thick-film functional coatings rather than decorative finishes.

Polyester: The most widely used resin chemistry for exterior powder coatings, offering excellent UV resistance, color retention, and weathering performance. Polyester powder coatings are the standard for architectural applications and are available in standard, superdurable, and hyperdurable grades.

Epoxy: A resin chemistry that provides outstanding adhesion, chemical resistance, and corrosion protection but has poor UV resistance. Epoxy powder coatings are used for interior applications, primers, and functional coatings where chemical resistance is more important than exterior weathering.

Hybrid: A powder coating formulation that blends polyester and epoxy resins, typically in a 50:50 to 70:30 ratio. Hybrids offer a balance of chemical resistance and decorative properties for interior applications such as furniture, appliances, and shelving.

Polyurethane: A resin chemistry that combines excellent exterior durability with superior surface smoothness and chemical resistance. Polyurethane powder coatings produce very smooth, high-quality finishes and are used for automotive, aerospace, and premium architectural applications.

Fluoropolymer: A family of high-performance resin chemistries including PVDF and FEVE that offer the ultimate in exterior weathering resistance. Fluoropolymer coatings maintain color and gloss for 30+ years and are specified for premium architectural facades and curtain walls.

PVDF (Polyvinylidene Fluoride): The most common fluoropolymer used in architectural coatings, typically applied as a liquid coating in a 70% PVDF/30% acrylic formulation. PVDF coatings are the benchmark for long-term exterior color retention and are specified under AAMA 2605 and similar premium standards.

Cross-linking: The chemical reaction during curing in which polymer chains form bonds with each other, creating a three-dimensional network. Cross-linking transforms the melted powder from a thermoplastic state into a permanent thermoset film with enhanced hardness, chemical resistance, and durability.

Resin: The primary film-forming component of a powder coating that provides the coating's fundamental properties including adhesion, flexibility, hardness, and chemical resistance. The resin type — polyester, epoxy, hybrid, or fluoropolymer — determines the coating's performance characteristics.

Pigment: The component of a powder coating that provides color and opacity. Pigments are finely ground inorganic or organic particles that are dispersed throughout the resin matrix. Inorganic pigments generally offer better UV stability and heat resistance, while organic pigments provide brighter, more saturated colors.

Additive: A minor component added to a powder coating formulation to modify specific properties. Common additives include flow agents (for surface smoothness), degassing agents (to prevent pinholes), UV stabilizers (for enhanced weathering), and texture agents (for matte or textured finishes).

Pretreatment Terms

Conversion Coating: A chemical treatment applied to a metal surface that converts the outer layer of the metal into a stable compound that promotes coating adhesion and corrosion resistance. Common conversion coatings include zinc phosphate, iron phosphate, chromate, and chrome-free alternatives based on titanium or zirconium chemistry.

Zinc Phosphate: A crystalline conversion coating formed by treating steel with a zinc phosphate solution. Zinc phosphate provides excellent adhesion promotion and corrosion resistance and is the standard pretreatment for steel components requiring high-performance coating systems, particularly for exterior and automotive applications.

Iron Phosphate: An amorphous conversion coating formed by treating steel with an iron phosphate solution. Iron phosphate is simpler and less expensive than zinc phosphate but provides lower corrosion resistance. It is suitable for interior applications and mild environments where the performance demands are less stringent.

Chromate Conversion Coating: A conversion coating based on hexavalent or trivalent chromium compounds, historically the standard pretreatment for aluminum. Chromate coatings provide excellent adhesion and corrosion resistance but hexavalent chromium is toxic and carcinogenic, leading to its phase-out under REACH and other environmental regulations.

Chrome-Free Pretreatment: Modern conversion coating technologies based on titanium, zirconium, or silane chemistry that replace traditional chromate processes. Chrome-free pretreatments meet or exceed the performance of chromate systems while eliminating the health and environmental risks of hexavalent chromium. They are now the standard for architectural aluminum coating.

Degreasing: The first step in most pretreatment processes, involving the removal of oils, greases, and other organic contaminants from the metal surface using alkaline cleaners, solvent cleaners, or aqueous detergent solutions. Thorough degreasing is essential because any residual contamination will prevent proper adhesion of subsequent conversion coatings and powder coatings.

Acid Etch: A pretreatment step in which the metal surface is treated with an acidic solution to remove the natural oxide layer and create microscopic surface roughness. On aluminum, acid etching with phosphoric or chromic acid solutions produces a clean, uniformly roughened surface that promotes mechanical adhesion of the conversion coating and powder coating.

Anodizing (as pretreatment): While primarily a standalone finish, anodizing can also serve as a pretreatment for subsequent coating. The porous anodic oxide layer provides an excellent mechanical key for paint or powder coating adhesion, and the oxide itself provides additional corrosion protection beneath the topcoat.

Performance Terms

Adhesion: The strength of the bond between the coating and the substrate, measured by standardized tests such as the cross-cut test (ISO 2409) and pull-off test (ISO 4624). Good adhesion is fundamental to coating performance — without it, the coating will peel, flake, or blister regardless of its other properties.

Salt Spray Test: An accelerated corrosion test (ASTM B117, ISO 9227) in which coated panels are exposed to a continuous salt fog at 35°C. The test measures the coating system's resistance to corrosion by evaluating creep from a scribed line, blistering, and general corrosion after specified exposure periods, typically 500-2,000 hours for architectural coatings.

Weathering: The degradation of a coating caused by exposure to outdoor environmental factors including UV radiation, moisture, temperature cycling, and atmospheric pollutants. Accelerated weathering tests using QUV chambers or xenon arc lamps simulate years of outdoor exposure in weeks, allowing coating durability to be predicted and compared.

Chalking: A form of coating degradation in which the surface breaks down into a fine, powdery residue. Chalking is caused primarily by UV radiation breaking down the resin binder at the coating surface, releasing pigment particles. It is most pronounced in epoxy coatings and is minimal in quality polyester and fluoropolymer coatings.

Gloss Retention: The ability of a coating to maintain its original gloss level over time when exposed to weathering. Gloss retention is measured by comparing the specular gloss (at 60° angle) of weathered samples to the original gloss, expressed as a percentage. High gloss retention indicates superior UV resistance and resin stability.

Color Retention: The ability of a coating to maintain its original color over time when exposed to weathering. Color retention is quantified by measuring the color difference (Delta E) between the original and weathered coating using a spectrophotometer. Lower Delta E values indicate better color stability.

Delta E: A numerical value representing the total color difference between two color measurements in the CIE Lab* color space. A Delta E of 1.0 is approximately the smallest difference perceptible to the trained human eye. Architectural coating standards typically require Delta E values below 3-5 after specified weathering exposure periods.

UV Resistance: The ability of a coating to withstand degradation from ultraviolet radiation without significant color change, gloss loss, or chalking. UV resistance is determined by the resin chemistry, pigment selection, and UV stabilizer additives used in the coating formulation.

Corrosion Resistance: The ability of a coating system to prevent corrosion of the underlying metal substrate. Corrosion resistance depends on the entire system — pretreatment, primer (if used), and topcoat — and is evaluated through salt spray testing, cyclic corrosion testing, and real-world exposure trials.

Standards Terms

Qualicoat: An international quality label organization that sets standards for powder and liquid coated aluminum used in architecture. Qualicoat licenses coating applicators who meet its requirements for equipment, processes, and quality control, and classifies coatings into Class 1 (standard durability), Class 2 (superdurable), and Class 3 (hyperdurable) based on weathering performance.

GSB: Gtegemeinschaft fr die Stckverzinkung und Beschichtung — a German-based international quality association for coated aluminum and steel. GSB certifies coaters and classifies coatings as GSB Master (standard), GSB Florida (enhanced durability), and GSB Premium, with testing requirements that complement and in some areas exceed Qualicoat standards.

AAMA: The American Architectural Manufacturers Association, which publishes voluntary performance specifications for architectural coatings in North America. Key specifications include AAMA 2603 (basic performance), AAMA 2604 (high performance), and AAMA 2605 (superior performance, typically fluoropolymer), each defining increasingly stringent weathering and durability requirements.

FGIA: The Fenestration and Glazing Industry Alliance, formed by the merger of AAMA and IGMA. FGIA maintains the AAMA coating specifications and other fenestration industry standards, serving as the primary standards body for window, door, and curtain wall products in North America.

ISO 12944: An international standard that provides guidance on corrosion protection of steel structures by protective paint systems. It classifies environments into corrosivity categories (C1 through CX) and specifies coating system durability ranges (low, medium, high, very high), helping specifiers select appropriate coating systems for specific exposure conditions.

ASTM B117: The standard practice for operating salt spray (fog) testing apparatus, widely used to evaluate the corrosion resistance of coated metal specimens. While ASTM B117 is a test method rather than a pass/fail specification, it is referenced by numerous coating standards and specifications as the basis for corrosion resistance evaluation.

Euroclass: The European fire classification system defined by EN 13501-1, which classifies building materials and products based on their reaction to fire. Classes range from A1 (non-combustible) to F (no performance determined), with additional classifications for smoke production (s1-s3) and flaming droplets (d0-d2).

EPD (Environmental Product Declaration): A standardized, third-party verified document that reports the environmental impact of a product over its lifecycle, based on Life Cycle Assessment (LCA) methodology. EPDs for powder coatings quantify impacts such as carbon footprint, energy consumption, and resource depletion, supporting green building certifications like LEED and BREEAM.

RAL: A German color matching system that is the most widely used color standard in the European coating industry. The RAL Classic collection contains 215 standardized colors, each identified by a four-digit number. RAL colors provide a universal reference for specifying and communicating coating colors across manufacturers, applicators, and projects.

Finish Terms

Gloss: A finish with high specular reflectance, typically measuring above 80 gloss units (GU) at a 60° angle. Gloss finishes produce a shiny, reflective surface that enhances color depth and vibrancy. They show surface imperfections and fingerprints more readily than lower-gloss alternatives.

Matte: A finish with very low specular reflectance, typically measuring below 20 GU at 60°. Matte finishes produce a flat, non-reflective surface with a contemporary, understated aesthetic. They are effective at hiding minor surface imperfections and are popular in modern architectural design.

Satin: A finish with moderate specular reflectance, typically measuring 30-50 GU at 60°. Satin finishes offer a subtle sheen that balances the visual depth of gloss with the practicality and contemporary feel of matte. Satin is one of the most popular finish choices for architectural powder coating.

Texture: A finish with a deliberately roughened or patterned surface, achieved through the use of texture-producing additives in the powder formulation. Textures range from fine sand to coarse wrinkle and provide practical benefits including hiding surface imperfections, reducing fingerprint visibility, and improving scratch resistance.

Metallic: A finish containing metallic flake pigments — typically aluminum, copper, or mica particles — that create a sparkling, light-reflective effect. Metallic powder coatings add visual depth and movement to surfaces and are popular for automotive, furniture, and architectural accent applications.

Pearlescent: A finish containing mica-based interference pigments that produce a color-shifting, iridescent effect as the viewing angle changes. Pearlescent finishes create a sophisticated, premium appearance with subtle color play and are used for high-end architectural and automotive applications.

Sublimation: A heat-transfer process used to apply photographic-quality patterns — most commonly wood grain — to powder coated surfaces. A printed transfer film is wrapped around the coated part and heated, causing the sublimation inks to vaporize and penetrate into the powder coating, creating a permanent, embedded pattern.

Wood Grain: A finish that replicates the appearance of natural timber species such as oak, walnut, cherry, or teak on metal substrates. Wood grain finishes are produced through sublimation transfer technology and are widely used for aluminum windows, doors, cladding, and fencing where a timber aesthetic is desired with metal durability.

Anodized-Look: A powder coating finish designed to replicate the appearance of anodized aluminum, including the characteristic metallic depth and subtle color variation. Anodized-look powder coatings offer a wider color range and more consistent appearance than actual anodizing, while providing the thicker protective film of powder coating.

Wrinkle: A textured finish with a distinctive crinkled or hammered appearance, produced by specific additives that cause the coating to shrink unevenly during curing. Wrinkle finishes are highly effective at hiding surface imperfections and are commonly used for industrial equipment, toolboxes, and decorative metalwork.