Industrial-grade 97% Lead oxide 1314-41-6

 What is lead tetroxide/red lead? How does it work?

Lead tetroxide (chemical formula Pb₃O₄, CAS 1314-41-6, common names red lead, lead oxide, bright lead oxide) is a mixed oxide of lead (Pb(II) to Pb(IV) molar ratio 2:1) and is a bright red to orange-red powder.

Basic information: Molecular formula Pb₃O₄, molecular weight 685.60, CAS number 1314-41-6, EC number 215-235-6, PubChem CID 16685188; Produced industrially by calcining and oxidising lead monoxide (PbO) in air at about 450–480℃ (6PbO + O₂ → 2Pb₃O₄). The natural mineral is called minium, and forms only under extreme oxidation conditions and is very rare.

It is a bright red to orange-red powder, it has a density of about 8.3 g/cm³, a melting point of about 500℃ (on heating it decomposes to lead monoxide and oxygen, and is completely decomposed at 580℃), it is almost insoluble in water and ethanol but soluble in hydrochloric acid (can be dissolved by gastric acid, therefore it is toxic if swallowed), it is soluble in glacial acetic acid and a mixture of nitric acid and hydrogen peroxide. 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 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 and can be used as such. Storage should be protected from moisture and heat, and away from reducing agents and flammable materials.

Definitions of Grades: This article is a complete version. All common grades of lead tetroxide are covered in this article, including industrial grade (rust-preventive coatings, lead-acid batteries, glass ceramics, electronic ceramics, rubber, fireworks, etc.), reagent grade (analytical grade/superior grade, used as analytical reagents and lead standard substances), etc. Note that its use in food, medicine and cosmetics is strictly prohibited. No food grade or food additive grades exist.

Lead tetroxide is irreplaceable from the viewpoint of its mechanism of action, because of its “oxidizing property + lead ion coordination and mixed-valence structure”. The mechanisms of action in different applications are:

1. 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 make lead soap which further increases adhesion. It’s the key pigment in a classic steel anti-rust primer.

2. 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) positive electrode active material by chemical formation treatment. This material is used in the charge and discharge reaction and is the lead source raw material used for the production of lead-acid batteries.

3. Mechanism of Piezoelectric and Electronic Ceramics Red lead as a source of lead enters perovskite structures like lead zirconate titanate (PZT). It has strong piezoelectric and ferroelectric properties, and lead ions are located in the A sites, so it is an important raw material for ceramic capacitors, ceramic filters and piezoelectric ceramics.

4. Regulation mechanism of glass network Lead ions have huge charge and are highly polarisable. Upon entering the glass network, they can significantly improve the refractive index and glossiness, reduce the melting temperature, and improve the electrical insulation and radiation absorption capacity. They are used in the formulation of crystal glass, optical glass and radiation-shielding glass.

5. Curing mechanism of chloroprene rubber It is used as a curing agent for chloroprene rubber and synergistically crosslinks with magnesium oxide. The substitution of the pure magnesium oxide system can greatly improve the water resistance and ageing resistance of the product.

6. Mechanism of oxygen release and high temperature decomposition Lead tetroxide decomposes at 500℃ to give oxygen and lead monoxide. It is an oxidiser and can be used as an oxidiser and combustion aid in pyrotechnic delay fuses and explosion effects (dragon eggs).

To summarise, lead tetroxide is a “classic lead-based material”. Also widely used in anti-rust primers, lead-acid batteries, piezoelectric ceramics, glass glazes, neoprene rubber and fireworks fuses, it covers corrosion protection, energy, electronics, building materials, chemicals and scientific research due to its oxidising properties and mixed-valence lead structure.

What are the uses of lead tetroxide / Red lead?

1. Primer pigments for rust inhibition (main application in the coatings industry)

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 rust prevention of steel. (The use of this pigment is limited by regulations due to the toxicity of lead and is being replaced by lead-free rust preventive pigments.)

2.Lead-acid battery production (core application in battery industry)

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, and positive electrode paste for energy storage batteries, etc.

Applicability Principle: Red lead and other lead oxides are converted into positive electrode paste and then converted into lead dioxide by formation. Lead dioxide is the active material for the positive electrode, participating in charge-discharge cycles. It is one of the main raw materials for the lead source in the manufacturing of lead-acid batteries.

3.Electronic ceramics and piezoelectric components (important applications in the electronics industry)

Application Field: Electronic ceramics, piezoelectric devices.

Corresponding Products: Lead zirconate titanate (PZT) piezoelectric ceramics, piezoelectric igniters, piezoelectric buzzers, ceramic filters, ceramic capacitors, ultrasonic transducers, piezoelectric sensors, high frequency ceramic dielectrics, etc.

Applicability Principle: Red lead is employed as the lead source and integrated into the PZT perovskite structure. Lead ions occupy the A sites which make it have strong piezoelectric and ferroelectric properties. It is one of the key raw materials of piezoelectric ceramics and ceramic filters.

4.Lead glass and optical glass (glassmaking)

Application Field: Glass manufacturing industry

Corresponding Products: Crystal glass, optical glass, high refraction glass, electron tube glass, radiation shielding glass (X-ray/gamma-ray protective windows), lighting glass, glass ornament, glass enamel frit, etc.

Applicability Principle: Lead ions are highly polarisable and when added to the glass network they greatly increase the refractive index and shine, reduce the melting temperature and improve electrical insulation and radiation absorption properties. They are an important component in the formulation of crystal glass, optical glass and radiation shielding glass.

5.Ceramic glazes, enamels and colourants (ceramic industry)

Application Field: Manufacture of ceramics, enamel and glass. Corresponding Products: ceramic glaze, coloured glazes, art ceramic glazes, enamel pigments, enamel glaze, cloisonne enamel glaze, glass glaze, ceramic pigments fluxes, low temperature glaze, 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 the lead and cadmium leaching limits and are gradually becoming lead-free).

6.Chloroprene rubber curing agent (rubber industry)

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 greatly improves the water resistance and ageing resistance of products compared with the system of only magnesium oxide.

7. Fireworks and pyrotechnics Industry Application Field: Fireworks, pyrotechnics.

Corresponding Products: Firework delay charges, crackling microstars, fireworks powder components, ignition powder etc

Applicability Principle: Lead tetroxide decomposes at 500℃, releasing oxygen and has oxidising properties. It may be used in delay charges and crackling effects and provide a stable oxidant for fireworks formulas and control the combustion rate (it is limited in use in fireworks due to its toxicity).

8.Red lead for the fitter's mark (the field of machine work)

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 rubbed on the mating surfaces and scraped off shows definite colour at the contact points and does not flow readily under pressure. Scraping, alignment and inspection of machine tool guideways and mating surfaces. Largely replaced by engineer's blue now but red lead marking is more accurate.

9.Analytical Reagents and Laboratory Applications (Analytical Chemistry)

Application Field: scientific research and analytical chemistry laboratories.

Corresponding Products: Reagents for determining lead content, Lead standard solutions, Lead tetroxide analytical grade, Reagents for mineral analysis, Reagents for steel analysis, Teaching reagents for laboratories, etc.

Applicability Principle: Reagent-grade lead tetroxide has high purity and defined composition, making it suitable as a standard substance and reagent for lead analysis, ensuring accurate detection (strict lead protection is required when operating).

10. Creation of art and art pigments (in the fields of fine arts and conservation of cultural relics)

Application Field: Art pigments, conservation of art and cultural relics.

Corresponding Products: Gold paint for manuscripts with few pigments, red pigment for ancient Roman frescoes, red lead paint for oil painting, vermilion paint (substitute for cinnabar), classic red paint for anti-rust, traditional pigments for cultural relic restoration, museum collection restoration materials, etc.

Applicability Principle: Red lead has a brilliant red colour, good hiding power, and forms a durable film with drying oils such as linseed oil. It has been used since ancient times as a red mineral pigment in frescoes, manuscripts and oil painting primers and is still used in cultural relic restoration according to traditional techniques (lead protection is required during restoration).

11.Scientific research and physics demonstrations (in scientific research and educational fields)

Application Field: Demonstration and research in physics teaching.

Corresponding Products: Lichtenberg pattern test powder, dielectric surface dust experiment materials, electrostatic discharge demonstration materials, high voltage discharge test powder, popular science experimental consumables, etc.

Applicability Principle: Red lead powder is a powder with a low conductivity, fine particles and a distinct colour. When sprinkled on the surface of dielectric materials, it can produce dendritic discharge patterns (Lichtenberg patterns) during high voltage discharge, used for studying the discharge characteristics of insulating materials and for physics teaching demonstrations (must be carried out under ventilated and protective conditions).

To summarise, lead tetroxide (CAS 1314-41-6) is a "classic lead-based material. It is used in eleven applications because of its oxidising properties and mixed-valence lead structure, including anti-rust primer pigments, lead-acid battery manufacture, electronic ceramics and piezoelectric components, lead glass and optical glass, ceramic glazes and enamel, neoprene rubber curing agents, pyrotechnic fuse oxidisers, red lead for metalworking marking, analytical reagents, art pigments, and scientific research.