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| Synonyms:Lead tetroxide Minium Red lead Molecular Formula:Pb₃O₄ Molecular Weight: 685.6 HS Code: 2824909000 Grade: Industrial grade97% Hazard Class: Class6.1 | |||||||||
1314-41-6
Boss Chemical
1314-41-6
Lead tetroxide (chemical formula Pb₃O₄, common name: red lead, lead oxide or bright lead, CAS 1314-41-6) is a mixed-valence oxide of lead (Pb(II) to Pb(IV) molar ratio 2:1), a bright red to orange-red powder. It is one of the oldest pigments ever used; the ancient Romans used it for frescoes, and mediaeval gilded manuscripts were called "miniatures" because of it. Today it is a classic pigment for rust inhibitive primers on steel structures, a feedstock for lead-acid batteries, a source of lead for piezoelectric ceramics and an industrial feedstock for glass, ceramics, rubber and fireworks.
Basic information: Molecular formula Pb₃O₄, molecular weight 685.60, CAS number 1314-41-6, EC number 215-235-6; Industrially produced by calcining and oxidising lead monoxide (PbO) in air at about 450–480℃ (6PbO + O₂ → 2Pb₃O₄). The natural mineral is called red lead (minium), which is extremely rare.
Physically, it is a bright red to orange-red powder, with a density of about 8.3 g/cm³; melting point about 500℃ (heating decomposes it into lead monoxide and oxygen, and at 580℃ it decomposes completely); it is almost insoluble in water and ethanol, soluble in hydrochloric acid (gastric acid can dissolve it, so it is toxic if taken orally), and soluble in glacial acetic acid and a mixture of nitric acid and hydrogen peroxide. The crystals are tetragonal at room temperature.
Lead tetroxide is chemically a mixed-valence oxide and can be formulated as lead(II) plumbate [Pb²⁺]₂[PbO₄]⁴⁻. It decomposes at 500℃ with evolution of oxygen to form lead monoxide. It reacts with nitric acid to give insoluble lead dioxide and lead nitrate. It reacts with iron and iron oxides to give insoluble iron(II/III) plumbate, which is the chemical basis for its anti-rust effect. It is an oxidising agent. Storage: Protect from moisture and heat; keep away from reducing agents and flammable materials.
Grade Definition: This article covers the industrial grade of lead tetroxide, including specifications of lead tetroxide for industrial applications such as rust preventive coatings, lead-acid batteries, glass ceramics, electronic ceramics, rubber, fireworks, etc. Lead monoxide, lead dioxide and metallic lead are tightly regulated. Reagent Grade is also available for analytical use. Lead tetroxide is not permitted for use in food, pharmaceuticals and cosmetics.
In terms of mechanism of action, industrial lead tetroxide plays an irreplaceable role due to its "oxidising properties + lead ion coordination and mixed-valence structure". The mechanisms of action in different applications are as follows:
Mechanism of rust prevention and passivation Red lead interacts with the surface of steel and iron oxides to produce an insoluble iron (II/III) lead salt passivation film that isolates water and oxygen and inhibits anodic corrosion. It reacts with oily base materials to form lead soap which further increases adhesion. It’s the key pigment in a classic steel anti-rust primer.
Active material mechanisms of lead-acid batteries Lead oxides such as red lead are used in the manufacture of lead-acid batteries to prepare positive electrode lead paste, which is converted to lead dioxide (PbO₂), the positive electrode active material, by chemical formation treatment. This material participates in charge and discharge reactions and serves as the lead-source raw material for the production of lead-acid batteries.
Mechanism of Piezoelectric and Electronic Ceramics Red lead acts as the lead source and enters perovskite structures such as lead zirconate titanate (PZT). It has strong piezoelectric and ferroelectric properties, and lead ions occupy the A sites, so it is an important raw material for ceramic capacitors, ceramic filters and piezoelectric ceramics.
Regulation mechanism of glass network The lead ion is highly polarisable and carries a large charge. When they enter the glass network, they can greatly increase the refractive index and glossiness, reduce the melting temperature and improve electrical insulation. They form part of the formulation of crystal glass and optical glass.
Curing mechanism of chloroprene rubber It is used as a curing agent for chloroprene rubber and synergistically crosslinks with magnesium oxide. Compared with the pure magnesium oxide system, it can greatly improve the water resistance and ageing resistance of the product.
Mechanism of oxygen release and high temperature decomposition Lead tetroxide decomposes at 500℃ to release oxygen and form lead monoxide. It has oxidising properties and can be used as an oxidant and combustion aid in pyrotechnic delay fuses and explosion effects (dragon eggs).
To put it simply, industrial lead tetroxide is a “classic industrial lead-based material.” Thanks to its oxidising properties and mixed-valence lead structure, it has found broad application in corrosion protection, energy, electronics, building materials and chemicals, ranging from anti-rust primers and lead-acid batteries to piezoelectric ceramics, glass glazes, neoprene rubber and fireworks fuses.
Industrial lead tetroxide has the following 9 application fields:
Application Field: Heavy duty anti-corrosion applications and rust preventive coatings
Corresponding Products: Red lead anti-rust primer, steel structure anti-rust paint, ship bottom anti-rust paint, bridge steel structure primer, storage tank pipeline anti-rust paint, oil-based red lead paint, industrial equipment primer, etc.
Applicability Principle: Red lead reacts with the surface of steel and iron oxides to form a passivation film of insoluble iron-lead salt which isolates water and oxygen and inhibits anodic corrosion. It also reacts with oil-based bases to form lead soaps, which enhance adhesion. It is the most classical pigment for steel rust prevention. (The use of this pigment is restricted by regulations due to lead toxicity and is being replaced by lead-free rust preventive pigments.)
Application Field: Lead-acid batteries, Energy storage.
Corresponding Products: automotive starting batteries, electric bicycle batteries, forklift and industrial batteries, UPS uninterruptible power supply batteries, backup power batteries, positive electrode paste for energy storage batteries, etc.
Applicability Principle: Red lead and other lead oxides are made into positive electrode paste and then converted into lead dioxide by formation treatment. Lead dioxide is the positive electrode active material and participates in charge-discharge cycles. It is one of the main lead-source raw materials for manufacturing lead-acid batteries.
Application Field: Electronic ceramics and piezoelectric devices.
Corresponding Products: Lead zirconate titanate (PZT) piezoelectric ceramics, piezoelectric igniters, piezoelectric buzzers, ceramic filters, ceramic capacitors, ultrasonic transducers, piezoelectric sensors, etc.
Applicability Principle: Red lead is used as the lead source and incorporated into the PZT perovskite structure. Lead ions occupy the A sites and endow the material with strong piezoelectric and ferroelectric properties. It is an important raw material for piezoelectric ceramics and ceramic filters.
Application Field: Glass industry.
Corresponding Products: crystal glass, optical glass, high-refraction index glass, electron tube glass, radiation shielding glass, lighting glass, glass ornaments, etc.
Applicability Principle: Lead ions have high polarisability. When incorporated into the glass network, they can greatly improve the refractive index and gloss, reduce the melting temperature and enhance electrical insulation and radiation absorption properties. They are important ingredients for producing crystal and optical glass.
Application Field: Manufacture of enamel and ceramics.
Corresponding Products: Coloured glazes, artistic ceramic glazes, enamel pigments, enamel glazes, ceramic pigment fluxes, low temperature glazes, etc.
Applicability Principle: Red lead is used as a flux and gloss component in glazes and enamels, lowering the firing temperature and increasing the gloss and colour vibrancy of the glaze. (Lead glazes for daily-use ceramics must meet lead and cadmium leaching limits and are gradually being replaced by lead-free alternatives.)
Application Field: Chloroprene rubber and special rubber areas.
Corresponding Products: Chloroprene rubber products, diving suits, chloroprene rubber wire and cable sheaths, seals and gaskets, adhesives, waterproof rubber products, conveyor belts, etc.
Applicability Principle: Red lead is used as a curing agent in chloroprene rubber and has a synergistic effect in promoting cross-linking with magnesium oxide. It significantly enhances the water resistance and ageing resistance of the products in comparison with the magnesium-oxide-only system.
Application Field: Fireworks and Pyrotechnics.
Corresponding Products: Firework delay charges, crackling microstars, fireworks powder components, ignition powder, etc.
Applicability Principle: Lead tetroxide decomposes at 500℃, releasing oxygen and exhibiting oxidising properties. It may be used in delay charges and crackling effects to provide a stable oxidant for fireworks formulas and control the combustion rate. (Its use in fireworks is restricted due to its toxicity.)
Application Field: Machining and assembly work.
Corresponding Products: Red lead for fitter marking, colour developer for mating surfaces, colour developer for scraping, colour developer for machine alignment, colour developer for assembly inspection, etc.
Applicability Principle: Red lead powder is smeared onto mating surfaces; after scraping, distinct colour appears at contact points and it does not flow readily under pressure. It is used for scraping, alignment and inspection of machine tool guideways and mating surfaces. It has been largely replaced by engineer's blue, though red lead marking delivers higher accuracy.
Application Field: Analytical Chemistry and Scientific Research Laboratory.
Corresponding Products: Lead tetroxide (analytical grade), Lead standard solutions, Reagents for determination of lead, Reagents for mineral analysis, Laboratory teaching reagents, etc.
Applicability Principle: Due to its high purity and definite composition, reagent-grade lead tetroxide can be used as a standard substance and reagent for lead analysis to ensure accurate detection. (Strict lead protection is required during operation.)
To summarise, industrial grade lead tetroxide (CAS 1314-41-6) is a “classic lead-based industrial material.” It features oxidising properties and a mixed-valence lead structure. It has nine mature applications: anti-rust primer pigment, lead-acid battery manufacturing, electronic ceramics and piezoelectric components, lead glass and optical glass, ceramic glaze and enamel, neoprene rubber curing agent, pyrotechnic fuse oxidiser, red lead marking for metalworking, and analytical reagent. The largest consumption volumes are for anti-rust primers and lead-acid batteries, while the highest value-added electronic application is for piezoelectric ceramics.
