BENZOTRIAZOLE

Benzotriazole is a nitrogen-containing aromatic heterocycle used primarily as a corrosion inhibitor and metal-passivation agent for copper, brass, bronze, silver and related non-ferrous metal systems. Benzotriazole has CAS Number 95-14-7, EC Number 202-394-1, molecular formula C6H5N3 and molecular weight approximately 119.12 g/mol. Benzotriazole is normally supplied as a white to off-white crystalline solid, powder, granule, needle or flake depending on commercial form, with a melting point around 96-100°C, density around 1.35-1.36 g/cm³ and significant water solubility near room temperature. The principal technical value of Benzotriazole comes from its strong interaction with copper surfaces and copper ions, producing an adsorbed and complexed protective film that suppresses oxidation, staining, pitting and metal dissolution. Benzotriazole is therefore widely relevant to cooling-water treatment, antifreeze and coolant formulations, metalworking fluids, hydraulic and heat-transfer fluids, copper and brass surface treatment, metal polishes, anti-tarnish systems, industrial cleaners, heritage conservation and specialty chemical synthesis. Because Benzotriazole is environmentally mobile and persistent enough to raise regulatory concern, and because current European assessment has concluded endocrine-disrupting properties for the environment, modern use should combine corrosion-performance design with careful discharge control, wastewater management and current regulatory review.

PRODUCT IDENTITY

Chemical Name: Benzotriazole
Preferred Specific Name: 1H-Benzotriazole
CAS Number: 95-14-7
EC Number: 202-394-1
Molecular Formula: C6H5N3
Molecular Weight: Approximately 119.12 g/mol
Chemical Class: Fused aromatic triazole / nitrogen heterocycle
Ring System: Benzene ring fused to a 1,2,3-triazole ring
Physical Form: Crystalline solid, powder, flakes, needles or granules depending on commercial form
Appearance: White to off-white or light-tan crystalline material
Odor: Essentially odorless to faint characteristic odor depending on grade
Melting Point: Commonly approximately 96-100°C; high-purity reference material is often near 98.5°C
Density: Approximately 1.35-1.36 g/cm³ around room temperature
Bulk Density: Commercial powder or granule bulk density depends strongly on particle form; reference laboratory material can be around 500 kg/m³
Water Solubility: Significant; published values commonly range from approximately 19-28 g/L near room temperature, with lower values also reported depending on method and form
Solubility in Organic Solvents: Soluble in alcohols and several polar or aromatic organic solvents
pKa: Approximately 8.2-8.4 for the weak-acid dissociation in water
Octanol/Water Partition Coefficient: Relatively low, with published log Kow values around approximately 1.1-1.3
Vapor Pressure: Low at room temperature
Thermal Behavior: Can decompose on strong heating; published boiling data vary because measurements are often under reduced pressure or affected by decomposition
Flash Point: High and method-dependent; published closed-cup values include approximately 170°C, while other reference methods report values above 200°C
Primary Function: Copper and copper-alloy corrosion inhibitor
Secondary Functions: Metal passivator, anti-tarnish additive, surface-treatment additive, corrosion-control component in coolants and industrial fluids, photographic antifoggant and specialty chemical intermediate
Principal Metal Targets: Copper, brass, bronze and other copper-containing alloys; silver protection is also technically relevant
Principal Current Industrial Areas: Water treatment, cooling systems, antifreeze and coolants, metalworking fluids, hydraulic fluids, heat-transfer systems, surface treatment, metal polishes, detergent anti-tarnish systems and chemical synthesis
Current EU Harmonized Classification at the Time of the 2026 CLH Proposal: Aquatic Chronic 2, H411
Current 2026 CLH Proposal Status: Opinion development; additional hazard classes have been proposed but are not yet final harmonized classifications
Environmental Endocrine-Disruptor Assessment Outcome: ED ENV concluded in the current European assessment process
Current Storage Principle: Store dry, tightly closed, protected from moisture, contamination, strong oxidizers and excessive heat

SYNONYMS

Benzotriazole, 1H-Benzotriazole, 1,2,3-Benzotriazole, Benzotriazol, 1,2,3-Benzotriazol, BTA, BTAH, Azimidobenzene, Aziminobenzene, Benzene Azimide, Benzene Azimide Compound, 1H-Benzo[d][1,2,3]triazole, Benzo[d][1,2,3]triazole, Benzotriazole 1H Form, Benzotriazole Corrosion Inhibitor, Benzotriazole Copper Inhibitor, Benzotriazole Copper Corrosion Inhibitor, Benzotriazole Metal Passivator, Benzotriazole Anti-Tarnish Agent, Benzotriazole BTA, BTA Corrosion Inhibitor, BTA Copper Passivator, Copper Corrosion Inhibitor BTA, Copper Passivator Benzotriazole, CAS 95-14-7, EC 202-394-1, C6H5N3, Benzotriazole Crystals, Benzotriazole Powder, Benzotriazole Granules

WHAT IS BENZOTRIAZOLE?

Benzotriazole is a fused aromatic nitrogen heterocycle consisting of a benzene ring joined to a five-membered 1,2,3-triazole ring.
The molecule contains three neighboring nitrogen atoms that provide strong coordination and adsorption capability toward copper-containing surfaces and ions.
This surface affinity is the basis of the most important commercial application: corrosion inhibition of copper and copper alloys.
Benzotriazole is effective because it can adsorb on metal, interact with surface copper species and form a compact copper-benzotriazole protective layer.
The protective film reduces access of oxygen, chloride and other corrosive species to active copper sites.
Benzotriazole is therefore best understood as a highly specialized yellow-metal inhibitor rather than as a general-purpose corrosion inhibitor for every metal.

MOLECULAR STRUCTURE

Benzotriazole contains a benzene ring fused to a 1,2,3-triazole heterocycle.
The triazole ring contains three nitrogen atoms with lone-pair and aromatic electronic character that enable adsorption and coordination at metal surfaces.
Benzotriazole can exist in tautomeric forms in which the ring proton is associated with different nitrogen atoms.
In aqueous solution the molecule behaves as a weak acid, with a pKa commonly reported around 8.2-8.4 for deprotonation.
Acid-base state influences solubility, adsorption and interaction with copper ions.
The aromatic fused-ring structure also gives Benzotriazole sufficient chemical stability for use in recirculating industrial-fluid systems.

PHYSICAL PROPERTIES

Benzotriazole is normally a crystalline solid at room temperature.
High-purity material typically melts close to 98°C, while commercial specifications can use a broader melting interval depending on purity and particle form.
The solid density is approximately 1.35-1.36 g/cm³ around room temperature.
Benzotriazole has low vapor pressure under ordinary storage conditions.
The material is substantially water soluble compared with many aromatic corrosion inhibitors.
Strong heating can cause decomposition, so thermal handling should follow product-specific safety guidance rather than relying on one nominal atmospheric boiling point.

MELTING POINT

Benzotriazole commonly melts in the approximate 96-100°C range.
High-purity reference material is often reported near 98.5°C.
A narrow melting range can provide a useful identity and purity indicator.
Organic impurities, residual solvent or isomeric contamination can shift or broaden the melting interval.
Molten processing is not required for most applications because Benzotriazole can be dissolved in water, alkaline solution or compatible organic carrier systems.

THERMAL BEHAVIOR

Published boiling-point data for Benzotriazole vary because measurements are reported at different pressures and the substance can decompose at elevated temperature.
Reduced-pressure data include boiling near approximately 204°C at about 15 mmHg.
Some atmospheric-pressure references give values in the approximately 350°C range, while international safety references emphasize decomposition around approximately 260°C.
For practical industrial use, decomposition behavior is more important than assigning one universal normal boiling point.
Unnecessary high-temperature exposure should therefore be avoided.

FLASH POINT

Benzotriazole has a relatively high flash point compared with conventional low-boiling organic solvents.
Published values differ with test method and commercial form.
Closed-cup data around approximately 170°C are widely reported, while other reference material gives values above 200°C.
The current product-specific SDS should control formal fire classification and handling limits.
Combustible dust and decomposition fumes should still be considered in hot or dusty operations.

DENSITY

The solid density of Benzotriazole is approximately 1.35-1.36 g/cm³ at room temperature.
Bulk density is lower because commercial powder, flake or granule beds contain void space.
Particle size and manufacturing form therefore influence packaging volume and feeder calibration.
Weight-based dosing is usually more reliable than volume dosing for solid corrosion-inhibitor concentrates.
The batch COA should be used where a specific bulk-density requirement is important.

WATER SOLUBILITY

Benzotriazole has significant water solubility compared with many aromatic heterocyclic corrosion inhibitors.
Published room-temperature values include approximately 19-28 g/L, although lower measured ranges have also been reported depending on method, purity and equilibrium conditions.
Solubility generally increases with temperature.
Alkaline conditions increase practical dissolution because deprotonated benzotriazolate species are more water compatible.
Commercial water-treatment formulations frequently use dissolved or neutralized Benzotriazole rather than adding coarse solid directly to a circulating system.
A clear concentrate should be checked for precipitation after cooling and after mixing with salts or other treatment chemicals.

PKA AND ACID BASE BEHAVIOR

Benzotriazole is a weak acid with a pKa commonly reported around 8.2-8.4 at room temperature.
Below this pH range the neutral form becomes increasingly important.
Above the pKa, deprotonated benzotriazolate species become increasingly significant.
Benzotriazole can also be protonated under strongly acidic conditions because the ring nitrogens can accept a proton.
This amphoteric-type acid-base behavior influences solubility and metal-complex chemistry.
Formulators should therefore evaluate final pH rather than assuming identical performance across acidic, neutral and strongly alkaline systems.

CORROSION INHIBITION MECHANISM

Benzotriazole protects copper through adsorption, coordination and protective-film formation at the metal surface.
The triazole nitrogen atoms interact strongly with copper and copper(I) species.
Surface complexes can polymerize or organize into an insoluble copper-benzotriazole layer.
The protective layer blocks active corrosion sites and restricts transport of oxygen, chloride and other aggressive species.
Research has described both chemisorption and formation of copper-benzotriazole complexes as important contributors.
The detailed molecular structure of the protective film can vary with oxidation state, pH, surface condition and solution composition.

COPPER FILM FORMATION

Copper exposed to Benzotriazole develops a thin protective surface layer.
The layer contains Benzotriazole coordinated with copper surface species and can strongly reduce copper dissolution.
Film formation can occur directly from inhibitor-containing water or through pretreatment of a clean copper surface.
Warm pretreatment solutions can accelerate film development in selected industrial or conservation processes.
The protective film is not equivalent to a thick paint coating; it is a chemically bound surface-passivation layer.
Film performance depends on surface cleanliness and the continuing chemical environment.

COPPER CORROSION CONTROL

Copper corrosion control is the most established Benzotriazole application.
The inhibitor can reduce general dissolution, staining, pitting and surface oxidation in appropriately treated systems.
Copper corrosion can release dissolved copper ions that subsequently plate onto steel and create galvanic attack elsewhere in a mixed-metal circuit.
Suppressing copper dissolution can therefore protect both the copper component and downstream ferrous equipment.
Benzotriazole dosage should be sufficient to satisfy both surface-film demand and any dissolved-copper demand in the circulating fluid.
Water chemistry, oxidants, chlorides and flow velocity all affect the required treatment program.

BRASS CORROSION CONTROL

Brass contains copper and responds well to triazole corrosion-inhibitor chemistry.
Benzotriazole can adsorb and complex at the copper-rich alloy surface.
This can reduce tarnishing and general corrosion in water, coolant and cleaning environments.
Brass composition, zinc content, dezincification risk and water chemistry still influence total corrosion behavior.
Benzotriazole should therefore be part of a complete water-treatment or fluid-formulation strategy rather than viewed as a universal solution to every brass-corrosion mechanism.

BRONZE PROTECTION

Bronze and copper-rich heritage alloys can be treated with Benzotriazole to reduce ongoing corrosion.
The material has long been used in conservation practice, particularly where active copper corrosion or so-called bronze disease is present.
Conservation treatment normally requires careful removal or stabilization of active corrosion products before inhibitor application.
Benzotriazole can penetrate porous corrosion layers and complex with copper species.
Heritage conservation should use controlled procedures because appearance, residual inhibitor and reversibility considerations differ from industrial water treatment.

SILVER AND ANTI-TARNISH USE

Benzotriazole also has technical relevance to silver and silver-containing surfaces.
The inhibitor can reduce tarnish or staining in selected detergent, cleaner, polish and protective formulations.
Dishwashing formulations have historically used triazole chemistry to reduce attack on decorative silver or silver-plated items.
The optimum concentration depends on surfactants, alkalinity, oxidants and wash temperature.
Strong oxidizing bleach systems can interact with or consume azole inhibitors, so compatibility should be demonstrated on the complete formulation.

APPLICATIONS

Cooling-water treatment
Benzotriazole is one of the most established copper and brass corrosion inhibitors in industrial cooling-water programs. Benzotriazole forms a protective surface film that reduces yellow-metal corrosion and dissolved-copper release.

Open recirculating cooling systems
Copper and brass heat-exchanger components in recirculating cooling water can be protected with Benzotriazole when inhibitor residual, oxidant demand and water chemistry are properly controlled.

Closed-loop cooling systems
Benzotriazole is useful in closed cooling circuits containing copper tubing, heat exchangers or brass fittings because the inhibitor can maintain a persistent protective film.

Electronic-equipment cooling systems
Copper cooling jackets and liquid-cooling loops can use Benzotriazole to suppress copper dissolution where fluid purity and inhibitor concentration are controlled.

Heat exchangers
Copper and copper-alloy heat exchanger surfaces can be passivated by Benzotriazole in cooling and heat-transfer circuits.

Chiller systems
Benzotriazole can be part of chiller-water treatment where copper tubes or brass components require corrosion protection.

HVAC systems
Closed and recirculating HVAC water systems can use Benzotriazole for yellow-metal protection when compatible with the complete inhibitor package.

Antifreeze formulations
Benzotriazole is used in antifreeze concentrates to protect copper and brass components in engine and industrial cooling circuits.

Automotive coolants
Engine coolants can use Benzotriazole or related azole inhibitors to reduce copper and brass corrosion, subject to the coolant specification and current 
restricted-substance requirements.

Industrial coolants
Industrial glycol or water-based coolant packages can include Benzotriazole for yellow-metal corrosion protection.

Ethylene glycol heat-transfer fluids
Benzotriazole is compatible with many inhibited glycol heat-transfer systems and can protect copper surfaces when dissolved and maintained at the required 
concentration.

Propylene glycol heat-transfer fluids
Selected propylene glycol systems can use Benzotriazole where yellow-metal compatibility and environmental requirements are satisfied.

Solar thermal fluids
Closed solar-heating loops containing copper components can use azole inhibitor chemistry in compatible heat-transfer formulations.

Hydraulic fluids
Benzotriazole can be incorporated into selected water-based or specialty hydraulic-fluid packages to protect copper-containing components.

Metalworking fluids
Benzotriazole is widely relevant to water-miscible and synthetic metalworking fluids where copper, brass or bronze components must be protected from 
staining and corrosion.

Machining fluids
Benzotriazole can reduce staining of copper and brass during cutting, grinding or machining operations.

Grinding fluids
Water-based grinding formulations can use Benzotriazole to protect yellow-metal workpieces and machine components.

Synthetic cutting fluids
Benzotriazole can be dissolved into synthetic metalworking concentrates where copper-alloy compatibility is required.

Semi-synthetic metalworking fluids
Azole corrosion inhibition can supplement emulsifier, buffer and biocide packages in semi-synthetic fluids.

Copper drawing fluids
Copper and brass forming operations can use Benzotriazole-containing fluids to reduce staining and oxidation.

Wire drawing
Copper wire-drawing systems can use passivating additives where residue and downstream process compatibility have been validated.

Metal cleaners
Benzotriazole can be added to alkaline or neutral metal-cleaning formulations to inhibit attack on copper and brass during cleaning.

Industrial detergents
Cleaning products used around mixed metals can include Benzotriazole to reduce yellow-metal corrosion.

Automatic dishwashing formulations
Triazole chemistry can help protect silver, copper-colored decorative metals and related surfaces from tarnish in aggressive wash environments.

Metal polishes
Benzotriazole can be incorporated into polishing formulations to provide residual copper or brass tarnish protection after cleaning.

Protective waxes
Metal waxes can include Benzotriazole as a passivating additive for copper-rich surfaces.

Copper polish formulations
Copper polishes can combine mechanical or chemical cleaning with Benzotriazole treatment to delay re-tarnishing.

Brass polish formulations
Brass-care products can use Benzotriazole where the final surface should remain bright after cleaning.

Anti-tarnish coatings
Thin protective coatings and conversion treatments can use Benzotriazole to increase tarnish resistance on copper and copper-alloy surfaces.

Copper surface pretreatment
Clean copper can be pretreated with Benzotriazole solution before storage, assembly or exposure to corrosive environments.

Brass surface pretreatment
Brass components can be passivated with Benzotriazole prior to packaging or subsequent processing.

Printed circuit manufacturing
Copper-containing electronic components can use benzotriazole-type passivation chemistry in selected manufacturing or cleaning steps, subject to 
electronics-process compatibility.

Electronic connectors
Copper and brass connector surfaces can benefit from anti-tarnish treatment where electrical-contact performance is not compromised.

Copper foil protection
Benzotriazole can reduce oxidation and staining of copper foil during storage or aqueous processing.

Electroplating baths
Selected plating and surface-finishing processes use Benzotriazole as a suppressor, passivator or corrosion-control additive where bath chemistry is 
compatible.

Post-plating treatment
Copper-containing plated parts can receive Benzotriazole passivation after rinsing to reduce staining during storage.

Jewelry and decorative metal protection
Copper, brass and bronze decorative items can be treated with Benzotriazole-containing formulations to slow tarnish.

Heritage conservation
Benzotriazole is used in conservation of archaeological and historic copper-alloy objects to stabilize active corrosion.

Bronze conservation
Bronze artifacts can be treated with Benzotriazole as part of controlled conservation procedures for active chloride-related corrosion.

Museum metal conservation
Conservators use Benzotriazole selectively to passivate copper-containing artifacts before protective coating or controlled storage.

Water-treatment concentrates
Benzotriazole can be blended into concentrated liquid or solid water-treatment products designed for copper and brass protection.

Yellow-metal inhibitor packages
Benzotriazole is a core component in treatment packages specifically designed for copper and copper-alloy systems.

Boiler auxiliary systems
Ancillary cooling or condensate equipment containing copper alloys can use Benzotriazole in compatible treatment programs, although main boiler chemistry requires separate evaluation.

Process-water systems
Industrial process-water loops containing copper heat-transfer surfaces can use Benzotriazole where discharge and environmental limits are controlled.

Fire-water and standby loops
Selected stagnant or intermittently used water circuits containing yellow metals can use Benzotriazole after microbiological, compatibility and discharge review.

Hydrotest fluids
Temporary aqueous hydrotest fluids can use Benzotriazole to reduce copper-alloy staining during test exposure.

Packaging corrosion protection
Benzotriazole can be incorporated into specialty corrosion-control formulations used around copper components during storage and shipping.

Vapor-phase inhibitor systems
Benzotriazole has historical relevance to vapor-phase or enclosed-package corrosion-inhibitor concepts, although actual delivery depends on formulation and volatility.

Photographic processing
Benzotriazole has long been used as an antifoggant or restrainer in silver-halide photographic processing because it can suppress unwanted silver development.

Photographic developers
Small controlled quantities can restrain fog formation in selected photographic developer formulations.

Silver-halide systems
Benzotriazole interacts with silver-containing photographic materials and can influence image and fog density.

Chemical synthesis
Benzotriazole is a useful nitrogen heterocycle and intermediate in specialty organic synthesis.

UV-absorber intermediates
Benzotriazole chemistry is used in the synthesis of hydroxyphenyl benzotriazole ultraviolet absorbers used in plastics and coatings; the simple parent 
Benzotriazole should not be confused with the finished UV absorber.

Pharmaceutical intermediates
Benzotriazole can serve as an intermediate or synthetic building block in specialty pharmaceutical chemistry.

Agrochemical intermediates
Benzotriazole chemistry can be used in the synthesis of specialty agrochemical and heterocyclic intermediates.

Dye and pigment intermediates
The triazole ring can serve as a building block in selected colorant and specialty-aromatic syntheses.

Research reagent
Benzotriazole is widely used in corrosion, coordination, photochemistry and heterocyclic-synthesis research.

Analytical reference material
High-purity Benzotriazole is used as an analytical reference standard for environmental and wastewater analysis.

COOLING WATER CORROSION CONTROL

Cooling systems containing copper or brass often require a dedicated yellow-metal inhibitor.
Benzotriazole is among the most effective aromatic triazoles for this purpose.
The inhibitor interacts with cuprous oxide and surface copper species to form a chemisorbed and complexed protective film.
Dissolved copper in the bulk water can consume part of the available Benzotriazole, creating an inhibitor demand before complete surface filming is achieved.
The treatment residual should therefore be monitored rather than assuming that the initial dose remains available indefinitely.
Water-treatment design should consider pH, chloride, sulfate, oxidant residual, conductivity, copper concentration, temperature and flow.

OPEN RECIRCULATING SYSTEMS

Open recirculating cooling systems continuously concentrate dissolved salts through evaporation.
Copper surfaces in heat exchangers can therefore experience chloride, sulfate, oxygen and oxidizing-biocide stress.
Benzotriazole can provide yellow-metal protection when a sufficient active residual is maintained.
Makeup water, blowdown and treatment-feed rates affect the inhibitor concentration.
Biofilm, suspended solids and corrosion products can interfere with clean surface filming.
A complete cooling-water program should therefore coordinate Benzotriazole with scale control, microbiological control and ferrous-metal corrosion inhibition.

CLOSED LOOP SYSTEMS

Closed cooling loops can provide favorable conditions for long-term Benzotriazole protection because inhibitor loss through blowdown is limited.
The initial treatment must still account for adsorption on metal and reaction with dissolved copper.
Leaks, makeup water and maintenance can dilute the inhibitor residual over time.
Routine analysis should confirm that the inhibitor remains above the validated minimum.
Closed systems containing glycol require compatibility testing because glycol, buffers and other inhibitors alter the total solution chemistry.

COPPER BTA COMPLEX FILM

A central concept in Benzotriazole performance is formation of a copper-BTA complex layer.
The layer is strongly adsorbed and can become polymeric or network-like on the metal surface.
This film reduces anodic copper dissolution and can also influence cathodic reactions.
The exact mechanism remains chemically complex, and scientific literature supports contributions from chemisorption, complex formation and electronic stabilization of surface oxides.
The practical result is lower corrosion rate when the film is continuous and chemically stable.

SURFACE CONDITION

Clean copper surfaces generally form protective Benzotriazole films more predictably than heavily fouled or oxidized surfaces.
Oil, grease, scale and thick corrosion deposits can prevent uniform access of the inhibitor to active metal.
Precleaning can therefore improve passivation.
Existing copper ions and corrosion products can also consume Benzotriazole.
In severely corroded equipment, the initial treatment demand can be higher than the maintenance demand after the surface stabilizes.

PH EFFECTS

Benzotriazole can protect copper over a broad pH range, but inhibitor chemistry changes with pH.
The molecule behaves as a weak acid with a pKa around 8.2-8.4.
At alkaline pH, benzotriazolate anion becomes increasingly important and can interact strongly with metal ions.
At lower pH the neutral form dominates.
Very aggressive acid or alkaline environments can alter both corrosion rate and film stability.
The complete treatment program should therefore be validated at the actual operating pH.

CHLORIDE EFFECTS

Chloride is a major driver of copper pitting and localized corrosion.
Benzotriazole can substantially reduce copper attack in chloride-containing water when the inhibitor film is maintained.
Higher chloride concentration can increase inhibitor demand and make defects in the film more consequential.
Flow and temperature can further increase mass transfer of corrosive ions.
Treatment residual should be evaluated under realistic chloride loading rather than only in deionized-water laboratory tests.

OXIDIZING BIOCIDE COMPATIBILITY

Oxidizing biocides can react with or deactivate triazole corrosion inhibitors.
Excessive chlorination is especially important because strong oxidizing conditions can reduce Benzotriazole protection and increase copper corrosion.
Cooling-water programs should coordinate oxidant dose, contact time and azole residual.
Shock treatment can require temporary adjustment or restoration of inhibitor concentration.
Compatibility should be established for chlorine, bromine, chlorine dioxide, peroxide or other oxidizing programs used at the site.

FLOW EFFECTS

Water velocity changes copper corrosion and inhibitor-film stability.
Research under flowing chloride conditions shows that Benzotriazole remains protective, but increasing flow can increase uninhibited corrosion severity.
High shear can expose defects or increase transport of chloride and oxygen to the surface.
Adequate inhibitor residual and clean film formation are therefore important in high-flow heat exchangers.
Laboratory static immersion data should not be the only basis for severe dynamic service.

ANTIFREEZE AND COOLANT FORMULATION

Benzotriazole is used in antifreeze and coolant packages to protect copper and copper-alloy components.
The inhibitor can be blended with glycol, buffers and inhibitors for aluminum, steel and other metals.
A mixed-metal coolant must balance all metal requirements because an additive favorable to copper is not necessarily sufficient for aluminum or cast iron.
Benzotriazole concentration should remain soluble across the full coolant concentration and temperature range.
Freeze-thaw cycling and hard-water dilution can influence precipitation and corrosion performance.
Coolant qualification should use recognized corrosion tests appropriate to the equipment.

METALWORKING FLUID FORMULATION

Benzotriazole can prevent staining of copper and brass during metalworking.
Water-miscible machining fluids may contain amines, surfactants, lubricants, buffers and biocides that influence Benzotriazole solubility and adsorption.
The inhibitor should remain available in the aqueous phase and should not precipitate during concentrate dilution.
Copper corrosion tests and stain tests should be performed at the actual use dilution.
Biocide and oxidant compatibility should also be checked because aggressive chemistry can reduce azole effectiveness.

DETERGENT AND CLEANER FORMULATION

Alkaline cleaners can attack copper and silver surfaces even when the detergent performs well on soils.
Benzotriazole can reduce this unintended metal attack.
The inhibitor must remain soluble in the detergent concentrate and use solution.
High alkalinity, chelants and oxidizing bleach can change film formation.
Silver-protection claims should be tested with the actual wash cycle, temperature and detergent composition.

METAL POLISHES AND WAXES

Benzotriazole can be applied after cleaning to delay re-tarnishing of copper and brass.
Wax and polish carriers can deposit the inhibitor together with hydrophobic protective components.
The metal surface should be free from abrasive residue and active cleaner before passivation.
Too much residual inhibitor or incompatible carrier can alter gloss or leave haze.
Decorative formulations should therefore be optimized for both corrosion protection and appearance.

HERITAGE CONSERVATION

Benzotriazole is one of the best-known chemical treatments for copper-alloy conservation.
The inhibitor can stabilize copper chloride-related corrosion by interacting with copper ions and surfaces.
Treatment can be performed by immersion, brushing, local application or other controlled conservation methods.
Concentration, solvent, application time and subsequent coating depend on artifact condition.
Conservation work should consider appearance, porosity, residual chloride and ethical conservation requirements.
Industrial water-treatment practice should not be copied directly to museum objects.

PHOTOGRAPHIC USE

Benzotriazole has a long history as an antifoggant and restrainer in silver-halide photography.
The compound interacts with silver-containing surfaces and can suppress unwanted development.
Small concentration changes can alter image tone, development speed and fog density.
Photographic use therefore requires formulation-specific control rather than corrosion-inhibitor dosage logic.
Although traditional photographic demand has declined, the chemistry remains technically and historically important.

CHEMICAL INTERMEDIATE

Benzotriazole is also a useful building block in synthetic chemistry.
The ring nitrogens permit substitution and functionalization that lead to many specialty benzotriazole derivatives.
Hydroxyphenyl benzotriazole derivatives are widely used as ultraviolet absorbers in plastics, coatings and other materials.
The simple parent Benzotriazole should not be described as equivalent to these high-molecular-weight UV absorbers.
Benzotriazole can also appear in routes to pharmaceutical, agrochemical, dye and coordination-chemistry intermediates.

UV ABSORBER INTERMEDIATE

Benzotriazole chemistry is central to an important class of ultraviolet absorbers.
Hydroxyphenyl benzotriazoles contain additional aromatic and hydroxyl substituents that create strong ultraviolet absorption and excited-state proton-transfer behavior.
Those derivatives are chemically distinct from simple 1H-Benzotriazole.
Benzotriazole can therefore be described accurately as an intermediate or heterocyclic building block for UV-stabilizer chemistry rather than as a direct drop-in UV stabilizer for polymers.

DOSAGE PRINCIPLE

There is no single universal Benzotriazole dosage for all applications.
Cooling-water dose depends on copper surface area, dissolved copper, water chemistry, flow and oxidant demand.
Metalworking-fluid concentration depends on use dilution and copper-stain performance.
Polish, detergent and conservation systems use different contact times and carrier chemistries.
Published historical cooling-water examples include concentrations from tens to low hundreds of milligrams per liter, but these should not be copied blindly into current systems.
A validated treatment program should establish initial passivation dose, maintenance residual and analytical monitoring.

CONCENTRATE PREPARATION

Benzotriazole can be incorporated into water-treatment concentrates as solid, aqueous solution or neutralized soluble salt form.
Warm water, agitation and alkaline neutralization can improve dissolution.
Concentrates should be checked for crystal formation after cooling.
High salt concentration can reduce solubility through ionic-strength effects.
Mixing sequence should avoid local supersaturation.
Preservatives, surfactants and other treatment chemicals should be tested for compatibility.

ALKALINE SOLUTIONS

Alkaline solutions can improve practical Benzotriazole solubility because deprotonated benzotriazolate species form above the pKa.
Sodium or potassium hydroxide can be used in controlled formulation to prepare more water-compatible inhibitor concentrates.
Neutralization changes pH and ionic composition of the final product.
Strong caustic addition should be controlled because dissolution and heat evolution can be localized.
The final treatment solution should be evaluated for both copper protection and compatibility with the rest of the water-treatment package.

PRECIPITATION RISK

Benzotriazole can crystallize from concentrated solution when temperature, pH or salt content changes.
A clear warm concentrate may become supersaturated after cooling.
Acidifying a benzotriazolate solution can increase the neutral Benzotriazole fraction and reduce practical solubility.
Hard-water salts or other formulation components can also influence clarity.
Cold-storage testing should therefore be part of concentrate development.

ANALYTICAL MONITORING

Benzotriazole residual can be monitored in water-treatment systems using analytical methods selected for the concentration range and matrix.
High-performance liquid chromatography and related chromatographic methods are commonly used in environmental and laboratory analysis.
Field colorimetric or proprietary treatment-control methods may also be used in industrial programs.
Residual measurement is important because copper ions, surfaces, oxidants and blowdown can consume or remove inhibitor.
A treatment target should be based on active residual rather than only calculated feed.

QUALITY CONTROL

Important Benzotriazole quality-control parameters include identity, assay, melting range, appearance, color, moisture, ash, insoluble matter and particle form.
High-purity commercial material commonly uses assay specifications around 99% or higher, although exact industrial grades vary.
Melting range near approximately 96-100°C provides a useful identity and purity check.
Color is important in clear coolant, cleaner and surface-treatment formulations.
Moisture and insoluble matter can affect dissolution and concentrate clarity.
The current Ataman Chemicals specification and batch COA should control commercial acceptance.

ASSAY

Assay defines the proportion of Benzotriazole in the commercial grade.
Higher-purity material provides more predictable inhibitor activity and reduces unknown organic residue.
Corrosion performance should still be evaluated on the final formulation because purity alone does not define film formation.
Chromatographic assay can distinguish Benzotriazole from related organic impurities.
A batch COA should state the applicable test method and release limit where required.

MELTING RANGE AS QUALITY INDICATOR

A high-purity Benzotriazole sample normally melts close to approximately 98°C.
A broadened or shifted melting range can indicate impurities, residual solvent or mixed isomers.
Melting behavior is useful as a classical identity check.
Modern chromatographic and spectroscopic methods can provide complementary identity confirmation.

COLOR

Commercial Benzotriazole is typically white to off-white or light tan.
Darkening can indicate oxidation, thermal history or contamination.
Low color is especially important in clear coolants, metal polishes and high-appearance formulations.
The applicable color scale and maximum should follow the product specification.

MOISTURE

Moisture content can influence flowability, caking and precise assay on an as-received basis.
Very damp material can dissolve differently from dry material and can create storage caking.
Packaging should protect the solid from humid air and liquid contamination.
The product-specific moisture or loss-on-drying limit should be used where controlled.

PARTICLE FORM

Commercial Benzotriazole can be supplied as powder, flakes, granules or other low-dust solid forms.
Powder dissolves quickly but can create more airborne dust.
Granules improve flowability and can reduce dust during bag handling.
Flakes provide another compromise between dissolution rate and low-dust handling.
Particle form should match feeder design, dissolution equipment and workplace exposure controls.

CURRENT EU HARMONIZED CLASSIFICATION

As of October 2026, the harmonized classification identified in the current European CLH process includes Aquatic Chronic 2 with hazard statement H411.
H411 means toxic to aquatic life with long-lasting effects.
Commercial SDS documents can contain additional self-classified hazards such as acute oral toxicity and eye irritation based on supplier data.
The current product-specific regional SDS should therefore control workplace labeling while the harmonized-classification process is followed separately.
Environmental release prevention is essential regardless of the final outcome of the pending hazard proposal.

2026 CLH PROPOSAL

A 2026 European harmonized-classification dossier proposes substantial additional hazard classifications for 1H-Benzotriazole and its inorganic salts.
The proposal includes Acute Toxicity Category 4 by the oral route with H302.
The proposal includes Carcinogenicity Category 2 with H351.
The proposal includes Reproductive Toxicity Category 2 with H361d.
The proposal also includes environmental endocrine-disruptor Category 1 with EUH430, persistent-mobile-toxic classification with EUH450 and very-persistent-very-mobile classification with EUH451.
These are proposed classifications under opinion development and should not be described as final harmonized classifications as of October 2026.

CLH STATUS

The Benzotriazole harmonized-classification proposal entered public consultation in March 2026 and the consultation closed in May 2026.
The process remains in opinion development.
The legal deadline shown for scientific opinion adoption is July 2027.
Final harmonized classification can therefore change from the dossier proposal before regulatory adoption.
Current compliance documents should be reviewed periodically because the hazard profile is actively developing.

ENVIRONMENTAL ENDOCRINE DISRUPTION

The completed European endocrine-disruptor assessment has concluded that Benzotriazole has endocrine-disrupting properties for the environment.
The assessment outcome is identified as ED ENV.
This conclusion is distinct from the separate CLH process that proposes formal ED ENV 1 classification under the newer hazard framework.
Environmental endocrine activity strengthens the case for minimizing uncontrolled Benzotriazole discharge from cooling systems, cleaners, antifreeze, metalworking fluids and industrial wastewater.
Treatment programs should therefore include both corrosion-performance and environmental-release management.

PERSISTENCE AND MOBILITY

Benzotriazole is highly relevant to environmental monitoring because it is water soluble, relatively mobile and not readily removed by conventional wastewater treatment.
The low log Kow means the substance does not behave like a strongly hydrophobic contaminant that simply binds to sludge or sediment.
Benzotriazole has been detected in wastewater effluent, rivers and other surface-water systems.
The current 2026 hazard proposal includes PMT and vPvM classifications, reflecting concern about persistence and mobility.
Wastewater discharge and blowdown should therefore be managed under current local requirements rather than assuming dilution eliminates environmental concern.

AQUATIC TOXICITY

Benzotriazole is currently harmonized in the European Union as Aquatic Chronic Category 2, H411.
This means the substance is toxic to aquatic life with long-lasting effects.
Cooling-tower blowdown, antifreeze disposal and metalworking-fluid waste can become significant release pathways if not controlled.
The inhibitor's corrosion benefit does not justify direct discharge to drains or surface water.
Wastewater-treatment compatibility and discharge permits should be evaluated for the actual concentration and flow.

OCCUPATIONAL SAFETY

Commercial Benzotriazole SDS documents commonly classify the material as harmful if swallowed and as causing serious eye irritation in addition to aquatic hazard.
Some datasets also report concern for inhalation exposure to dust.
The exact workplace classification should follow the current regional SDS for the supplied grade.
Dust generation should be minimized through enclosed charging, local exhaust ventilation and low-dust particle form.
Suitable gloves and eye protection should be used during handling.
Good hygiene is important because powder can transfer from gloves or work surfaces to the mouth.

FIRST AID

After eye contact, rinse cautiously and thoroughly with clean water and obtain medical attention if irritation persists or as directed by the current SDS.
After skin contact, wash exposed skin with water and remove contaminated clothing.
After inhalation of dust, move the affected person to fresh air and obtain medical advice if symptoms occur.
After accidental ingestion, rinse the mouth and contact a poison center or medical professional according to the current SDS.
Do not induce vomiting unless specifically directed by medical guidance.

SPILL MANAGEMENT

Avoid generating airborne dust when collecting spilled Benzotriazole solid.
Prevent the material from entering drains, soil, surface water and groundwater.
Use dry mechanical collection, suitable chemical vacuum equipment or compatible absorbent for dissolved product where appropriate.
Recovered material should be placed in a labeled container for reuse only if quality and contamination controls permit; otherwise manage it as waste.
Contaminated wash water should not be discharged uncontrolled because Benzotriazole is environmentally mobile and aquatic-toxic.
Current SDS and local environmental requirements should govern cleanup and disposal.

FIRE RESPONSE

Benzotriazole is a combustible organic solid with a relatively high flash point.
Fine dust can behave differently from bulk crystalline material and should not be allowed to accumulate around ignition sources.
Strong heating can cause decomposition and release nitrogen oxides and other irritating fumes.
Firefighters may require self-contained breathing apparatus and appropriate protective clothing.
Extinguishing media should be selected according to the surrounding fire and the current SDS.
Closed containers exposed to fire should be cooled when this can be done safely.

STORAGE

Benzotriazole should be stored in tightly closed compatible packaging in a dry, cool and well-ventilated area.
The product should be protected from moisture, strong oxidizing agents, excessive heat and contamination.
Direct sunlight and repeated temperature cycling should be minimized where they affect color or caking.
Powder and granule packaging should be resealed promptly after partial use.
Storage areas should prevent uncontrolled release to drains in the event of a spill.
The current package label and Ataman Chemicals SDS should control shelf-life and storage details for the supplied grade.

INCOMPATIBILITIES

Benzotriazole should be kept away from strong oxidizing agents.
Strong oxidants can degrade triazole chemistry and can also destroy corrosion-inhibitor performance in operating water systems.
Very strong acids or bases alter the protonation state and can change solubility and reaction behavior.
Metal salts can complex with Benzotriazole and may cause precipitation or consume active inhibitor.
Formulation compatibility should therefore be tested rather than inferred solely from individual raw-material solubility.

ENVIRONMENTAL MANAGEMENT

Environmental management is especially important for Benzotriazole because the substance is used in applications that can generate aqueous discharge.
Cooling-water blowdown, used antifreeze, metalworking-fluid disposal and cleaner wastewater should be treated as controlled release pathways.
Source reduction, inhibitor-recovery strategies, optimized residual control and appropriate wastewater treatment can reduce environmental loading.
Excessive feed should be avoided because corrosion protection eventually reaches a practical plateau while discharge mass continues to rise.
Analytical monitoring can support both process control and environmental compliance.

REGULATORY CONSIDERATIONS

Benzotriazole is undergoing active European hazard-classification development.
As of October 2026, Aquatic Chronic 2 H411 is the existing harmonized classification identified in the current CLH record.
Additional classifications including H302, H351, H361d, EUH430, EUH450 and EUH451 are proposed but are not yet final harmonized classifications.
The environmental endocrine-disruptor assessment has separately concluded ED ENV.
Customers should review current regional SDS, REACH obligations, wastewater requirements and customer restricted-substance lists before supply or use.
Future classification changes can affect labeling, workplace controls, substitution decisions and discharge management.

COMMON FORMULATION PROBLEMS

Benzotriazole does not dissolve completely
The concentration may exceed room-temperature solubility or the water can be too cold. Increase temperature, agitation or controlled alkaline neutralization and then verify cold-storage stability.

Crystals form after cooling
A warm concentrate can become supersaturated at lower temperature. Reduce concentration or adjust pH and solvent balance.

Crystals form after acidification
Lower pH increases the neutral Benzotriazole fraction and can reduce practical solubility. Improve dilution and avoid local acid over-concentration.

Cooling-water copper corrosion remains high
The active residual may be too low, copper ions may be consuming inhibitor or the surface may be fouled. Measure residual and inspect water chemistry rather than only increasing feed blindly.

Copper corrosion rises after chlorination
Strong oxidizing biocide can deactivate triazole inhibitor. Coordinate chlorine or bromine dose with Benzotriazole residual and treatment timing.

Brass still tarnishes
Surface contamination, inadequate passivation time or insufficient inhibitor concentration can produce incomplete film coverage. Clean and revalidate treatment conditions.

Copper concentration in water remains high
Existing corrosion deposits and dissolved copper can create a large initial inhibitor demand. Continue controlled passivation while monitoring both copper and active inhibitor.

Steel corrosion increases downstream
Dissolved copper can plate onto steel and create galvanic attack. Improve copper corrosion control and review the ferrous-metal inhibitor program.

Benzotriazole residual drops rapidly
Surface adsorption, dissolved copper, oxidants, blowdown or biological/chemical degradation can consume inhibitor. Identify the dominant loss mechanism.

Coolant develops haze
Benzotriazole can precipitate because of concentration, low temperature, hard-water salts or additive incompatibility. Conduct concentrate and dilution 
stability testing.

Antifreeze forms sediment
Check inhibitor solubility across glycol concentration, water hardness and temperature. Avoid over-concentrated solid addition.

Metalworking fluid stains copper
The use-dilution inhibitor level may be insufficient or the fluid pH and biocide package may interfere with film formation. Test at actual dilution.

Metalworking concentrate is clear but use dilution is hazy
Hard water, pH change or additive interactions can reduce Benzotriazole solubility. Test with representative plant water.

Cleaner attacks brass
High alkalinity, chelants or oxidant can overpower the inhibitor. Increase protection only after checking cleaner chemistry and metal exposure.

Dishwashing formulation tarnishes silver
Bleach or alkalinity may consume the triazole. Optimize anti-tarnish chemistry on the complete detergent formulation.

Metal polish leaves haze
Too much Benzotriazole, incomplete cleaning or incompatible wax carrier can leave visible residue. Reduce level and optimize application.

Conservation treatment changes bronze appearance
Surface porosity, corrosion products and solvent choice can change visual response. Use conservation-specific test areas before full treatment.

Benzotriazole powder cakes
Moisture, pressure or temperature cycling can cause caking. Improve packaging and dry-storage control.

Powder generates excessive dust
Use granule or flake form where available and improve enclosed charging and local exhaust ventilation.

Assay is below specification
Check moisture, related organic impurities and analytical method. Hold the batch until identity and purity are confirmed.

Melting range is broad
Organic impurities, residual solvent or mixed material can broaden the melting interval. Confirm purity by chromatography or spectroscopy.

Product becomes yellow or tan
Thermal history, oxidation or trace impurities can increase color. Review storage and production conditions.

Copper inhibitor performance differs between batches
Compare assay, moisture, particle form, dissolution and actual water chemistry. Corrosion performance is a system property, not only a raw-material 
property.

Water-treatment feed point causes local crystals
The concentrate can encounter unfavorable pH or high salt concentration before dilution. Improve injection location and mixing.

High chloride overwhelms passivation
Increase monitoring and optimize the total water-treatment program; severe chloride loading can require more than Benzotriazole alone.

Very high flow causes copper loss
Flow increases mass transfer and can challenge film defects. Validate inhibitor residual under actual velocity rather than static beaker conditions.

Benzotriazole is described as a UV stabilizer
Simple Benzotriazole is mainly a corrosion inhibitor and synthetic building block. Hydroxyphenyl benzotriazole derivatives are the established polymer UV 
absorbers.

Environmental discharge exceeds target
Reduce unnecessary overfeed, optimize residual control and improve wastewater or blowdown management. Benzotriazole is mobile and aquatic-toxic.

Wastewater treatment removes little Benzotriazole
Conventional treatment can provide incomplete removal. Evaluate source control and treatment technologies appropriate to the discharge requirement.

Customer asks whether Benzotriazole is an endocrine disruptor
The current European environmental assessment has concluded ED ENV. Formal CLH classification as ED ENV 1 is proposed and remains under opinion development 
as of October 2026.

Customer asks whether Benzotriazole is carcinogenic
Carcinogenicity Category 2 H351 is proposed in the 2026 CLH dossier but is not yet a final harmonized classification as of October 2026.

Customer asks whether Benzotriazole is reproductive toxicant
Reproductive Toxicity Category 2 H361d is proposed in the 2026 CLH dossier but is not yet final harmonized classification as of October 2026.

SDS classifications differ between suppliers
Self-classified hazards can differ while harmonized classification and scientific review evolve. Use the current regional SDS for the supplied grade and distinguish it from pending CLH proposals.

Corrosion inhibitor concentration is copied from another system
Copper area, dissolved copper, pH, oxidants, chloride, temperature and flow differ between systems. Determine dose through actual treatment testing and monitoring.

Benzotriazole is proposed for food-contact water without review
Industrial corrosion-inhibitor use does not establish suitability for potable-water or direct food-contact applications. Use only where current regulatory approval and system documentation support the application.

FREQUENTLY ASKED QUESTIONS

What is Benzotriazole?
Benzotriazole is an aromatic 1,2,3-triazole heterocycle used primarily as a corrosion inhibitor for copper and copper alloys.

What is the CAS Number?
95-14-7.

What is the EC Number?
202-394-1.

What is the molecular formula?
C6H5N3.

What is the molecular weight?
Approximately 119.12 g/mol.

What is another common name?
1H-Benzotriazole and 1,2,3-Benzotriazole are common names; BTA and BTAH are common abbreviations.

What is the physical form?
A white to off-white or light-tan crystalline solid supplied as powder, flakes, needles or granules depending on commercial form.

What is the melting point?
Commonly approximately 96-100°C, with high-purity material often near 98.5°C.

What is the density?
Approximately 1.35-1.36 g/cm³ around room temperature.

Is Benzotriazole soluble in water?
Yes. Published room-temperature values commonly fall around approximately 19-28 g/L, although measured values vary with method, purity and pH.

What is the pKa?
Approximately 8.2-8.4 for the weak-acid dissociation.

What is the main use of Benzotriazole?
The main use is corrosion inhibition and passivation of copper, brass and related copper alloys.

How does Benzotriazole protect copper?
It adsorbs and complexes with copper surface species to form a thin protective copper-benzotriazole film that reduces metal dissolution and oxidation.

Can Benzotriazole protect brass?
Yes. Brass is a major application because the copper-rich alloy surface responds well to triazole passivation.

Can Benzotriazole protect bronze?
Yes. It is used industrially and in heritage conservation for copper-rich bronze surfaces.

Can Benzotriazole protect silver?
It can provide anti-tarnish protection in selected cleaner, detergent and surface-treatment formulations.

Is Benzotriazole used in cooling water?
Yes. Benzotriazole is a standard yellow-metal inhibitor in many cooling-water and closed-loop treatment programs.

Is Benzotriazole used in antifreeze?
Yes. Benzotriazole is used in antifreeze and coolant formulations to protect copper and brass components.

Is Benzotriazole used in metalworking fluids?
Yes. It is used to reduce copper and brass staining and corrosion in water-based machining and grinding fluids.

Can Benzotriazole be used in hydraulic fluids?
Yes, in compatible specialty hydraulic-fluid formulations where copper protection is required.

Can Benzotriazole be used in detergents?
Yes. Triazole chemistry is used in selected detergents and cleaners to reduce attack on silver, copper and brass.

Is Benzotriazole a UV stabilizer?
Simple Benzotriazole is primarily a corrosion inhibitor. Hydroxyphenyl benzotriazole derivatives are the established polymer UV absorbers.

Is Benzotriazole used in photography?
Yes. It has a long history as an antifoggant or restrainer in silver-halide photographic systems.

What is the current EU harmonized classification?
As of October 2026, the current harmonized classification identified in the CLH record includes Aquatic Chronic 2, H411.

What new EU classifications are proposed?
The 2026 dossier proposes Acute Tox. 4 H302, Carc. 2 H351, Repr. 2 H361d, ED ENV 1 EUH430, PMT EUH450 and vPvM EUH451 in addition to Aquatic Chronic 2 H411.

Are those proposed classifications final?
No. As of October 2026 the CLH process remains in opinion development, with scientific opinion due by July 2027.

Has an environmental endocrine-disruptor assessment been completed?
Yes. The current European assessment has concluded ED ENV for Benzotriazole.

Is Benzotriazole hazardous to aquatic life?
Yes. The current harmonized classification includes Aquatic Chronic 2, H411, meaning toxic to aquatic life with long-lasting effects.

Is Benzotriazole persistent in wastewater systems?
Benzotriazole is environmentally mobile and can be incompletely removed in conventional wastewater treatment, which is one reason release control is important.

How should Benzotriazole be stored?
Store it cool, dry and tightly closed, protected from moisture, strong oxidizers, excessive heat and contamination.

What documents should be checked before use?
Use the current Ataman Chemicals TDS, SDS and COA together with current regional chemical, environmental and discharge requirements.

FINAL TECHNICAL SUMMARY

Benzotriazole is a defined aromatic heterocycle with CAS Number 95-14-7, EC Number 202-394-1, molecular formula C6H5N3 and molecular weight approximately 119.12 g/mol.
The material is normally a white to off-white crystalline solid with melting point around 96-100°C and density around 1.35-1.36 g/cm³.
Benzotriazole has significant water solubility, commonly reported in the approximate 19-28 g/L range near room temperature, and behaves as a weak acid with pKa around 8.2-8.4.

The principal industrial function is corrosion inhibition of copper, brass, bronze and related copper alloys.
Benzotriazole interacts with surface copper species to form a strongly adsorbed copper-benzotriazole protective film that suppresses oxidation, dissolution, staining and pitting.
Important applications include cooling-water treatment, closed-loop systems, HVAC, antifreeze and coolants, metalworking fluids, hydraulic fluids, heat-transfer fluids, industrial cleaners, metal polishes, anti-tarnish systems, surface treatment and heritage conservation.
Benzotriazole also has historical use as a photographic antifoggant and is an important synthetic building block for specialty benzotriazole derivatives.
Simple Benzotriazole should not be confused with hydroxyphenyl benzotriazole UV absorbers used directly as polymer light stabilizers.
Cooling-water performance depends on pH, chloride, dissolved copper, oxidant residual, temperature, surface condition and flow.

Strong oxidizing biocides can consume or deactivate azole inhibitor and should be coordinated carefully with the corrosion-control program.
Benzotriazole residual should be monitored because metal surfaces, dissolved copper, blowdown and oxidants can reduce the active concentration.
As of October 2026, the current EU harmonized classification identified in the active CLH record includes Aquatic Chronic 2 H411.
A 2026 harmonized-classification dossier additionally proposes Acute Tox. 4 H302, Carc. 2 H351, Repr. 2 H361d, ED ENV 1 EUH430, PMT EUH450 and vPvM EUH451.
Those additional classifications remain proposed and are not final harmonized classifications as of October 2026 because the process is still in opinion development.

The separate European environmental endocrine-disruptor assessment has concluded ED ENV.
Benzotriazole is environmentally mobile, is incompletely removed in many conventional wastewater systems and has been detected in surface water, so uncontrolled discharge should be minimized.
Quality control should include identity, assay, melting range, appearance, color, moisture, insoluble matter and particle form according to the agreed commercial specification.

For Benzotriazole technical specifications, corrosion-inhibitor formulation support, TDS, SDS, COA and commercial supply, contact Ataman Chemicals with the intended metal, water chemistry, application system, target concentration and regulatory market.

Ataman Chemicals
Phone: +90 216 577 10 10
Email: info@atamankimya.com