The Language of Finishing: Paint and Coatings Glossary I–K

This installment of the AirSprayTech.com Paint and Coatings Industry Glossary covers terms beginning with I, J, and K. These definitions focus on coating application, surface preparation, inspection, corrosion protection, spray equipment, electrostatic finishing, fire-protective coatings, and jobsite safety.

Coating terminology can have slightly different meanings depending on the industry, specification, or manufacturer. Contractors, inspectors, operators, and facility owners should always consult the project specification, approved product data sheets, safety data sheets, equipment manuals, and referenced standards before performing coating work.

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I

ICRI — International Concrete Repair Institute

Industry areas: Concrete coatings, floor coatings, containment linings, parking structures, waterproofing, and concrete repair.

ICRI is an industry organization that develops guidance for evaluating, preparing, repairing, and protecting concrete. Coating professionals commonly encounter the ICRI Concrete Surface Profile, or CSP, system when a specification defines the required texture of prepared concrete.

The CSP system uses numbered visual and tactile reference profiles. A higher number represents a more aggressive surface texture. The correct profile depends on the coating, overlay, lining, or repair material being applied. Learn more from the International Concrete Repair Institute.

Impact Resistance

Industry areas: OEM finishing, automotive, rail, aerospace, appliances, flooring, pipelines, and protective coatings.

Impact resistance is a coating system’s ability to withstand a sudden mechanical blow without cracking, chipping, delaminating, or losing adhesion. A coating may have excellent hardness but poor impact resistance if the film is too brittle to deform with the substrate.

Impact testing commonly involves dropping a standardized weight onto a coated test panel. The panel is then examined for cracking, detachment, or loss of adhesion. Direct-impact and reverse-impact results should not be treated as interchangeable.

One commonly referenced method is ASTM D2794, Resistance of Organic Coatings to the Effects of Rapid Deformation.

Impingement

Industry areas: Tank linings, marine coatings, wastewater facilities, pipelines, process equipment, and power generation.

Impingement occurs when a moving liquid, gas, slurry, or stream of particles strikes a coated surface with concentrated force. It can produce erosion, localized wear, coating undercutting, or premature coating failure.

Impingement service can be more severe than ordinary immersion because the coating must resist both chemical exposure and mechanical force. Nozzles, elbows, pump housings, vessel inlets, and areas below discharge points are common impingement zones.

Immersion Service

Industry areas: Tanks, vessels, pipelines, wastewater treatment, marine structures, secondary containment, and process equipment.

Immersion service means that a coating will be continuously or intermittently submerged in water, chemicals, fuel, wastewater, or another liquid. Immersion places different demands on a coating than ordinary atmospheric exposure.

A coating suitable for atmospheric service is not automatically suitable for immersion. Selection must consider the liquid, concentration, temperature, pH, frequency of exposure, pressure, cleaning procedures, and possibility of chemical mixtures.

An immersion coating generally must achieve its required cure before the vessel or structure is placed into service. Filling a tank too soon can cause softening, blistering, discoloration, loss of adhesion, or chemical attack.

Incomplete Cure

Industry areas: All liquid and powder coating operations.

Incomplete cure means a coating has not developed the physical or chemical properties expected from the specified curing process. The film may remain soft, tacky, easily marked, solvent-sensitive, weakly adhered, or unusually susceptible to water and chemicals.

Possible causes include incorrect mixing, an improper component ratio, inadequate induction time, expired material, low temperature, insufficient ventilation, excessive film thickness, contamination, or inadequate oven time or metal temperature.

Surface dryness alone does not prove complete cure. Verification may include hardness testing, solvent-resistance testing, temperature records, recoat response, or another procedure specified by the coating manufacturer.

Induction Time

Also called: Sweat-in time or maturation time.

Induction time is the required waiting period after the components of certain multi-component coatings have been mixed but before application begins. This waiting period allows necessary chemical reactions to start and helps the mixed coating reach the proper application condition.

Induction time is not the same as pot life. Induction time occurs before application, while pot life is the limited period during which the mixed coating remains usable. Required induction time may change with material temperature, so the product data sheet must be followed.

Industrial Coating

Industrial coating is a broad term for a coating applied to manufactured products, equipment, structures, or facilities to provide protection, appearance, identification, or a specialized functional property.

Examples include coatings for machinery, railcars, aircraft components, bridges, storage tanks, steel buildings, pipelines, agricultural equipment, wood products, appliances, and factory-finished components.

Industrial coatings may be applied by conventional air spray, HVLP, airless, air-assisted airless, electrostatic spray, powder spray, dip coating, flow coating, roll coating, or electrodeposition.

Inhibitive Coating

An inhibitive coating is designed to slow corrosion through chemical or electrochemical action at the substrate. Inhibitive primers are commonly applied to steel and other metals as one part of a complete protective coating system.

The term does not mean that the coating can compensate for inadequate surface preparation. Performance still depends on proper cleaning, surface profile, film thickness, cure, environmental control, and compatibility with subsequent coats.

Inlet Pressure

Inlet pressure is the air or fluid pressure measured at the entrance to a spray gun, pump, regulator, filter, or another piece of application equipment. It is important to distinguish inlet pressure from pressure measured at the compressor, pump outlet, or another upstream location.

Air pressure can drop through undersized hoses, long hose runs, restrictive fittings, filters, and quick connectors. For meaningful setup and troubleshooting, pressure should be measured while the equipment is operating at its normal flow rate.

Injection Injury

Industry areas: Airless and air-assisted airless spraying, plural-component equipment, sealant dispensing, and high-pressure fluid systems.

A high-pressure injection injury occurs when pressurized coating, solvent, grease, hydraulic fluid, or another material penetrates the skin. The entry wound may look minor even though substantial internal tissue damage has occurred.

A suspected injection injury is a medical emergency. The injured person should obtain immediate emergency medical care and provide medical personnel with the product label and safety data sheet.

Never place a hand or finger over a leaking fitting or spray tip. Never attempt to stop a high-pressure leak with a rag, glove, or body part while the system is pressurized.

Inorganic Zinc Coating

Also called: Inorganic zinc-rich primer or IOZ.

An inorganic zinc coating contains a high concentration of zinc dust held in an inorganic binder, commonly a silicate. When properly applied to prepared steel, the zinc can provide galvanic, or sacrificial, corrosion protection.

These coatings generally require carefully controlled abrasive-blast cleaning and surface profile. Application thickness, moisture, ventilation, temperature, curing conditions, and the interval before topcoating can strongly affect performance.

Excessive film thickness may cause cracking or mud cracking. Before topcoating, the applicator may also need to address zinc salts, porosity, or air trapped in the zinc film. A mist coat is sometimes specified to reduce bubbling or pinholing in the topcoat.

Inspection

Inspection is the organized observation, measurement, testing, and documentation used to determine whether materials and workmanship comply with the governing specification and approved procedures.

A coating inspection may address surface cleanliness, surface profile, soluble salts, ambient conditions, material identification, mixing, thinning, spray setup, wet-film thickness, dry-film thickness, holidays, adhesion, curing, appearance, repairs, and final acceptance.

Inspection does not create quality by itself. Quality results from effective planning, suitable materials, qualified personnel, proper equipment, controlled application, and timely corrective action.

Inspection Area

An inspection area is a defined portion of the work grouped together for examination, measurement, or acceptance. It may be identified by square footage, component, elevation, production lot, work shift, tank section, room, railcar, or another logical division.

The specification should establish how inspection areas are selected and how many readings or tests are required within each area. Inspection areas should not be redefined after the results are known merely to make nonconforming measurements appear acceptable.

Inspection Hold Point

A hold point is a specified stage at which work must stop until a designated person or organization completes an inspection and authorizes the work to continue.

Typical coating hold points include acceptance of abrasive-blast cleaning, verification of environmental conditions, approval of stripe coating, examination before overcoating, holiday testing, and final inspection. Hold points should be identified during the pre-job meeting and included in the inspection plan.

Inspection Report

An inspection report is the permanent record of observed conditions, measurements, tests, materials, work activities, and acceptance decisions. A useful report distinguishes facts and instrument readings from opinions or assumptions.

Depending on the project, the report may include the date, time, location, component identification, weather, surface temperature, dew point, relative humidity, product batch numbers, mixing times, equipment used, calibration or verification records, film-thickness readings, photographs, defects, repairs, and signatures.

Inspector

A coating inspector is a person responsible for observing and documenting coating work and evaluating it against the project requirements. Depending on the contract, the inspector may represent the owner, contractor, manufacturer, engineering company, or an independent inspection organization.

An inspector does not automatically have authority to alter the specification, approve substitutions, or direct the contractor’s means and methods. Authority, responsibilities, and reporting relationships should be defined before work begins.

General inspection guidance can be found in ASTM D3276, Standard Guide for Painting Inspectors.

Insulating Coating

An insulating coating reduces the transfer of heat or electricity, depending on the intended service. The term should always be interpreted within the project context.

A thermal-insulating coating may be intended to reduce heat transfer, condensation, or personnel exposure to hot surfaces. An electrically insulating coating is designed to resist the movement of electrical current. Neither function should be assumed without supporting test data and a clearly defined service condition.

Intercoat Adhesion

Intercoat adhesion is the bond between one coating layer and the next. A failure between coating layers is an intercoat failure rather than a loss of adhesion directly from the substrate.

Poor intercoat adhesion can result from surface contamination, chalking, an exceeded recoat window, excessive cure, amine blush, overspray, inadequate cleaning, coating incompatibility, or failure to abrade a smooth surface when required.

Intercoat Contamination

Intercoat contamination is unwanted material deposited on a coating before the next coat is applied. Common examples include dust, abrasive, oil, moisture, salts, overspray, release agents, fingerprints, insects, and amine blush.

Contamination can interfere with adhesion, appearance, corrosion resistance, and holiday-free application. The surface should be inspected and cleaned using a method approved for the coating system before recoating.

Intermediate Coat

An intermediate coat is a coating layer applied between the primer and finish coat. It may build film thickness, increase barrier protection, improve chemical resistance, provide color contrast, or create a suitable surface for the finish coat.

In a high-performance coating system, the intermediate coat is an engineered part of the total system and should not be treated as an optional filler coat.

Internal-Mix Spray Gun

An internal-mix spray gun combines the coating and atomizing air inside the air cap or nozzle before the spray exits the gun. This differs from an external-mix gun, where atomizing air contacts the fluid outside the fluid nozzle.

Internal-mix guns may be suitable for certain specialized or higher-viscosity materials, but they can be more sensitive to clogging and may not provide the finish quality required for general production finishing.

Equipment selection should be based on the coating, required production rate, desired finish quality, and the spray equipment manufacturer’s recommendations.

Intumescent Coating

Industry areas: Structural steel, commercial buildings, petrochemical facilities, transportation, and passive fire protection.

An intumescent coating reacts to high heat by expanding and forming an insulating char. The char slows heat transfer to the protected substrate and helps the structural member retain its strength for a specified period.

Performance depends on the complete tested assembly, including the substrate, primer, intumescent layer, required dry-film thickness, reinforcing mesh where specified, and topcoat.

Applicators must follow the listed system and approved application instructions. A visually satisfactory film is not proof that the required fire rating has been achieved.

Ionization

Industry areas: Electrostatic liquid and powder coating.

Ionization is the process of giving an atom or molecule an electrical charge by adding or removing electrons. In electrostatic finishing, ionization helps impart an electrical charge to coating droplets or powder particles so they are attracted toward a grounded workpiece.

Effective electrostatic attraction depends on suitable grounding, coating conductivity, gun distance, part geometry, voltage, current, airflow, and booth conditions. Increasing voltage alone does not guarantee improved transfer efficiency.

Ionizing Electrode

An ionizing electrode is the high-voltage component of an electrostatic applicator that creates the electrical field used to charge the coating. It may be positioned near the spray tip or incorporated into the applicator’s design.

The electrode should be kept clean and maintained according to the equipment manufacturer’s instructions. Coating buildup, physical damage, improper grounding, or incorrect spacing can reduce charging performance or contribute to electrical discharge.

Iron Phosphate

Industry areas: OEM liquid finishing, powder coating, appliances, metal furniture, and general metal fabrication.

Iron phosphate is a chemical pretreatment used primarily on ferrous metal to improve coating adhesion and corrosion resistance. It also helps prepare the surface for consistent wetting by the coating.

A pretreatment process may include cleaning, rinsing, phosphating, additional rinsing, sealing, and drying. Control of concentration, pH, temperature, contact time, water quality, rinsing, and final surface cleanliness is essential.

Residual cleaner, poorly rinsed chemicals, flash rust, or contamination introduced after pretreatment can cause coating defects or premature failure.

Isolation Coat

An isolation coat is a separating layer applied between materials that might otherwise be incompatible. It may reduce solvent attack, prevent staining or bleeding, isolate an unknown existing finish, or provide a compatible surface for the next coat.

An isolation coat should not be assumed to solve every compatibility problem. A test patch and written coating manufacturer approval are recommended when the existing coating or substrate condition is uncertain.

ISO — International Organization for Standardization

ISO is an independent international organization that publishes consensus standards used in manufacturing, testing, quality management, corrosion protection, surface preparation, and coating inspection.

Project documents should identify the complete standard number, part, and edition. Requirements can differ between editions, and a general reference to “ISO standards” is not sufficiently specific.

Information about ISO standards is available from the International Organization for Standardization.

ISO 12944

ISO 12944 is a multi-part standard addressing the corrosion protection of steel structures by protective paint systems. Its parts cover subjects such as environmental classification, design considerations, surface preparation, coating-system selection, laboratory performance testing, execution, and inspection.

Coating systems are selected using factors that include the corrosivity category, expected durability range, substrate, exposure, surface preparation, application conditions, and maintenance strategy.

A durability range is a technical planning period and should not automatically be interpreted as a product warranty.

ISO 8501-1

ISO 8501-1 is a widely referenced visual standard for evaluating rust grades and preparation grades of uncoated steel and steel from which previous coatings have been removed.

It includes visual preparation grades associated with abrasive-blast cleaning and hand- or power-tool cleaning. The visual grade addresses visible surface condition. It does not by itself establish surface profile, soluble salt concentration, dust level, or freedom from invisible contamination.

Isocyanate

Industry areas: Automotive refinishing, aerospace, OEM finishing, floor coatings, industrial maintenance, and polyurethane coating systems.

Isocyanates are reactive chemical groups commonly found in hardeners or activators used with two-component polyurethane and polyurea materials. Exposure can affect the respiratory system, skin, and eyes and may lead to sensitization.

Work involving isocyanate-containing materials requires a properly developed safety program based on the product SDS, exposure assessment, ventilation, work practices, protective clothing, eye protection, and appropriate respiratory protection. Workers should not rely on odor as an exposure warning.

Employers and applicators should consult current information from OSHA’s Isocyanates Safety and Health Topics page and follow all applicable regulations.

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J

Japanese Industrial Standards — JIS

Japanese Industrial Standards are technical standards used for industrial products, processes, testing, and measurement in Japan. JIS references may appear in international equipment specifications, coating requirements, automotive standards, and inspection documents.

A specification should state the exact JIS designation and edition. A result obtained under one national or international standard should not be assumed equivalent to another without a documented technical comparison.

Job Hazard Analysis — JHA

A Job Hazard Analysis is a task-level review that breaks work into steps, identifies the hazards associated with each step, and establishes controls before work begins. Some organizations use the term Job Safety Analysis, or JSA, for a substantially similar process.

For coating work, a JHA may address respiratory exposure, flammable vapors, static electricity, high-pressure injection, abrasive blasting, confined spaces, work at height, heat stress, chemical contact, electrical equipment, noise, and material handling.

The JHA should reflect actual jobsite conditions and should be updated when materials, equipment, personnel, weather, or work activities change.

Job Safety Analysis — JSA

A Job Safety Analysis is a structured process for identifying hazards and defining safe procedures for a specific task. The terms JSA and JHA are often used interchangeably, although individual companies may define their formats differently.

A coating-related JSA should be reviewed with the people performing the work. A signed form alone is not a substitute for effective training, supervision, hazard control, and stop-work authority.

Job Specification

The job specification is the collection of written requirements governing a coating project. It may define surface preparation, approved materials, number of coats, film thickness, colors, environmental limits, application methods, inspection frequency, acceptance criteria, repairs, safety responsibilities, and required documentation.

When project documents conflict, the contractor should obtain written clarification through the project’s established communication process. Field personnel should not independently choose which conflicting requirement to follow.

Jobsite

A jobsite is the location where construction, maintenance, repair, installation, or field coating work is performed. The term is particularly appropriate for bridges, tanks, buildings, pipelines, roofs, floors, and other field-applied coating projects.

“Plant,” “shop,” or “production facility” is generally more appropriate for a permanent manufacturing or OEM finishing operation. Both “field” and “jobsite” are correct, but “jobsite testing” more clearly distinguishes on-location inspection from laboratory testing.

Joint

A joint is the location where two materials, components, or sections meet. Joints may be designed to remain rigid or to accommodate movement caused by temperature change, vibration, loading, shrinkage, or structural settlement.

Coating over a moving joint without the proper joint treatment can lead to cracking, splitting, or water intrusion. The joint design and expected movement should be understood before selecting a coating, sealant, reinforcement, or transition detail.

Joint Sealant

A joint sealant is a flexible material installed in a joint to limit the passage of water, air, chemicals, debris, or other substances while accommodating expected movement.

Sealants may be based on polyurethane, silicone, polysulfide, acrylic, or other technologies. Compatibility between the sealant, substrate, primer, and surrounding coating must be confirmed.

Some coatings should not be applied across flexible joints unless the complete detail has been designed and approved to accommodate movement.

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K

Key — Mechanical Key

A mechanical key is the surface texture, roughness, or profile that allows a coating, adhesive, or repair material to grip the substrate. Abrasive blasting, sanding, grinding, and concrete profiling are common methods of creating a mechanical key.

More roughness is not always better. The profile must be appropriate for the coating’s thickness and ability to wet the surface. A profile that is too deep may leave peaks insufficiently covered, while a profile that is too shallow may not provide adequate adhesion.

Key Coat

A key coat is a layer applied to promote adhesion between a substrate or existing coating and a subsequent coating. Depending on the industry, it may also be called a tie coat, bond coat, or adhesion-promoting coat.

The term is not defined identically by every manufacturer. The applicator should confirm the key coat’s required thickness, recoat interval, compatibility, and intended function before use.

Kilopascal — kPa

The kilopascal is a metric unit of pressure used on gauges, regulators, spray equipment, compressed-air systems, and technical data sheets. One kilopascal equals 1,000 pascals.

For practical conversion, 1 psi is approximately 6.895 kPa, and 100 kPa is approximately 14.5 psi.

Operators should verify the unit printed on a gauge before adjusting equipment. Confusing psi, bar, MPa, and kPa can result in serious equipment setup errors.

Kinetic Energy

Kinetic energy is the energy an object possesses because of its motion. In abrasive blasting, the velocity and mass of the abrasive particles help determine the energy delivered to the surface.

Abrasive type, particle size, air pressure, nozzle condition, nozzle distance, and angle of impact affect the cleaning rate and resulting surface profile.

Excessive energy can damage thin metal or create an unsuitable profile, while insufficient energy may leave rust, mill scale, or an inadequate anchor pattern.

Knife Adhesion Test

A knife adhesion test evaluates the adhesion of a coating by cutting into the film with a knife and attempting to lift or remove it from the substrate. The resistance encountered and the manner in which the coating breaks or separates are assessed.

The test is destructive and leaves a damaged area that normally requires repair. Results can be influenced by coating thickness, hardness, flexibility, cure, substrate, number of layers, knife condition, and operator technique.

A commonly cited method is ASTM D6677, Standard Test Method for Evaluating Adhesion by Knife. The specified rating system and project acceptance criteria should be documented before testing.

Knife-Grade Coating

A knife-grade coating is a high-viscosity, non-sag material formulated for application with a putty knife, trowel, squeegee, or similar tool. It may be used to fill voids, smooth transitions, cover weld irregularities, or reinforce localized areas.

Knife-grade products are common in lining, waterproofing, flooring, roofing, repair, and composite applications. The term describes application consistency and should not be assumed to identify a particular chemistry or performance level.

Knifing

Knifing is the process of applying or working a coating, filler, glazing compound, surfacer, or repair material with a flexible knife or blade. The technique may be used to fill pinholes, level minor defects, force material into voids, or produce a thin localized layer.

The repaired area should be properly prepared and feathered where required. Heavy knifing with an unsuitable material can trap solvent, shrink during cure, print through a finish coat, or create a visible edge.

Krebs Unit — KU

The Krebs Unit is a commonly used measurement of the viscosity of paints and related materials under defined test conditions. It is typically obtained with a Stormer-type viscometer.

KU values are frequently used for architectural and industrial coatings, but they should not be treated as direct equivalents of seconds measured with a flow cup or viscosity expressed in centipoise. Each method uses different test geometry and conditions.

Temperature strongly affects viscosity, so the test temperature and method should be reported with the result. One commonly referenced procedure is ASTM D562, Consistency of Paints Using the Stormer-Type Viscometer.

kV — Kilovolt

A kilovolt equals 1,000 volts. In electrostatic liquid and powder coating, kV describes the high electrical potential used to charge coating particles and create attraction toward a grounded workpiece.

Higher kV can increase charging and wraparound under suitable conditions, but maximum voltage is not always the best setting. Excessive voltage can contribute to back-ionization, poor penetration into recesses, uneven film build, or difficulty coating areas affected by the Faraday cage effect.

kV Adjustment

kV adjustment is the process of setting the output voltage of an electrostatic applicator for the part geometry, coating material, gun distance, conveyor arrangement, and desired deposition pattern.

Operators may use a higher setting on broad, open surfaces and reduce the voltage when coating corners, recesses, weldments, or complex shapes.

The best setting is the one that produces stable charging, effective penetration, uniform film build, and safe operation—not necessarily the highest available number.

kV and Microampere Control

Electrostatic systems may monitor or control both voltage in kilovolts and current in microamperes. Voltage establishes the electrical potential, while current reflects electrical charge movement within the system.

As a spray gun approaches a grounded part, current may rise and the effective voltage may fall. Modern controls can limit output or automatically adjust it to improve application stability.

Operators should understand the equipment manufacturer’s display and recommended settings rather than evaluating electrostatic performance from kV alone.

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Referenced Standards and Industry Resources

• International Concrete Repair Institute
• International Organization for Standardization
• AMPP Standards and Technical Resources
• ASTM D2794 — Impact Resistance of Organic Coatings
• ASTM D3276 — Guide for Painting Inspectors
• ASTM D6677 — Evaluating Adhesion by Knife
• ASTM D562 — Consistency Using a Stormer-Type Viscometer
• OSHA Isocyanates Safety and Health Information

Continue Building Your Coatings Vocabulary

Understanding industry terminology helps applicators, inspectors, equipment operators, specifiers, and facility owners communicate more accurately. Continue with the next installment of The Language of Finishing for definitions beginning with the letters L and M.

For assistance selecting professional spray guns, pumps, pressure equipment, powder coating systems, electrostatic equipment, spray booths, ovens, or genuine replacement parts, contact AirSprayTech.com—The Finishing Authority® at 817.490.1777.

Copyright © 2026 Azimuth Spray Systems, LLC. All rights reserved. AirSprayTech.com—The Finishing Authority®. No portion of this glossary may be reproduced, distributed, or republished without prior written permission.

Tags: paint coatings glossary I-K, industrial coating terms, coating inspection terms, immersion coating terminology, intumescent coating, inorganic zinc coating, isocyanate safety, knife adhesion test, electrostatic coating terms