Benzotriazole

Product Overview

1,2,3-Benzotriazole (BTA, C6H5N3) is the plating industry's standard anti-tarnish and corrosion-inhibition agent for copper and its alloys. A single BTA molecule is small enough to pack tightly on a copper surface, where it forms a transparent, self-repairing film only a few nanometers thick that stops oxygen, humidity and sulfur gases from reaching the metal. In a hardware plating line BTA earns its place in three everyday situations: protecting freshly copper-plated work that must wait before nickel (overnight racks, weekend barrels), stopping tarnish on brass and copper-tone finishes during storage and export packing, and acting as a functional component inside proprietary copper brighteners and process coolants. Market grades: technical BTA at ≥ 99% assay is the plating norm; cheaper grades carry higher sodium sulfate and organics that leave films or foam. BTA is directly water-soluble in warm water (about 2% at 25°C), which makes it far easier to handle than the alkali-soluble sulfur azoles.

Product Identity (Encyclopaedia Card)

What it is and what it does. Benzotriazole (BTA) is the copper corrosion inhibitor added to acid copper baths, to passivation rinses and to lacquer formulations, where it forms a protective film on the copper and zinc surface.

• White to pale yellow needle crystals; used at 20-200 mg/L in rinses and at low mg/L in plating baths.
• Forms a chemisorbed film on copper and on zinc that stops tarnishing and reduces staining of the plated parts.
• Also used in cooling-water treatment and in anti-tarnish papers and lacquers.

Typical Use in a Plating / Finishing Line

Safety, Handling & Storage

Quality Documents Shipped With Every Batch

Buyer Questions We Answer Every Week

How It Works: BTA Film Formation and Its Limits

BTA chemisorbs on copper and brass through its triazole ring and cross-links into a protective polymer film. Because the bond forms and repairs continuously at room temperature, a BTA dip does not need heat to work - but temperature and pH control decide whether the film is thick and uniform or patchy:

Standard verification is the same sulfur-vapor test used across the industry: a treated panel must stay bright over 30 minutes in dilute ammonium-sulfide vapor while an untreated panel darkens within minutes.

Working Concentrations on the Line

BTA is consumed almost entirely by drag-out. A dip tank that plates a known surface area loses roughly 5-15 g per 1000 dm² of work; top up to keep the measured concentration, and carbon-polish the tank monthly to remove oils that block film formation.

Quality Checks Before Use

How QLQ controls it: every lot is assay-verified and H2S-vapor tested on copper panels against a retained reference before release. Because a contaminated BTA lot (high sulfate, organics) shows up first as patchy tarnish on a customer's parts, the batch number travels with each drum and QLQ keeps a retained sample for 12 months for re-testing.

Common Problems & Fixes (Workshop Table)

Handling & Safety

• Health: BTA is a mild irritant; wear gloves and a dust mask when weighing, and avoid inhaling the powder. Wash hands after handling.
• Fire note: BTA is combustible as a dust - keep away from open flame and strong oxidizers; do not sweep into a dusty bin near ignition sources.
• Dissolving: add to warm water (50-60°C) with stirring; stock solutions of 5-10% are convenient for dosing. Do not boil - BTA sublimes slowly above 100°C.
• Storage: sealed drums in a cool, dry store. BTA is stable for 24 months sealed; protect from humidity and direct sun.
• Waste: dilute BTA dips are biodegradable, but used baths carry copper - treat as metal-bearing waste or recover the copper before discharge.

What It Does on Iron, Zinc Alloy, Copper and Stainless Steel Parts

FAQ

Copper finish tarnishing in humid weather or export? QLQ engineering runs H2S-vapor testing and humidity trials for plating customers in 10+ countries. Contact us with a sample of the failing part.