A material once regarded as a secret weapon for high-end equipment is moving beyond niche applications and becoming increasingly important across industrial sectors. That material is perhydropolysilazane, commonly known as PHPS.

With its distinctive molecular structure and ability to convert into a dense inorganic ceramic layer, PHPS offers a new approach to corrosion protection under high temperatures, aggressive chemicals and other demanding operating conditions.

1. What Is Perhydropolysilazane?

Perhydropolysilazane is a fully inorganic ceramic precursor polymer. Its molecular structure contains only silicon, nitrogen and hydrogen, without any carbon-chain organic side groups. Its backbone consists primarily of high-bond-energy silicon–nitrogen covalent bonds.

Under normal conditions, PHPS is a transparent, low-viscosity liquid. It can undergo hydrolysis and crosslinking through exposure to moisture in the air, heat or ultraviolet radiation. After curing, it is converted into a dense inorganic ceramic film composed mainly of silicon dioxide and silicon nitride.

This conversion mechanism helps prevent the thermal decomposition, swelling and performance degradation commonly associated with organic resin coatings at elevated temperatures.

2. Why Is PHPS Becoming Important in Industrial Corrosion Protection?

2.1 Strong Chemical Inertness

The cured PHPS ceramic film forms a dense three-dimensional network with extremely low porosity. It can resist penetration during extended exposure to environments ranging from strong acids at pH 1 to strong alkalis at pH 13.

The ceramic layer also remains stable when exposed to aromatic hydrocarbons, glacial acetic acid, thiocyanates and other aggressive media, without the swelling commonly seen in some organic coatings.

Conventional epoxy and polyurethane coatings may blister or delaminate after several months of exposure to high-temperature steam. Silicate coatings, meanwhile, may provide limited resistance to certain organic solvents. A properly formulated PHPS ceramic layer offers a more durable barrier against the penetration of corrosive substances.

2.2 Stability Across a Wide Temperature Range

PHPS-derived ceramic films can remain stable during long-term use at temperatures of approximately 400°C in air. Under inert atmospheres, their temperature resistance can exceed 1,000°C.

The coating does not readily decompose or release volatile organic compounds at high temperatures. It can also withstand repeated heating and cooling cycles without developing significant cracks, making it suitable for heat exchangers, industrial furnaces and equipment exposed to alternating temperature conditions.

2.3 High Hardness and Resistance to Wear

A PHPS coating cured at elevated temperatures can reach a pencil hardness of up to 9H, while its mineral hardness approaches that of corundum.

This hardness enables the coating to resist erosion by moving materials, dust and flowing media. It can therefore be used on the inner walls of pipelines, towers and vessels where prolonged abrasion could otherwise expose the substrate.

The coating can also achieve Grade 0 adhesion in cross-cut testing. Chemical bonding with carbon steel, stainless steel and cast iron substrates helps reduce the risk of peeling around welded joints, flanges and other difficult-to-coat areas.

2.4 Dense Barrier Performance and Weather Resistance

The permeability of PHPS ceramic films to water molecules, chloride ions and small organic-solvent molecules can be approximately one-twentieth that of conventional anticorrosive coatings.

Salt spray resistance may exceed 3,000 hours under suitable formulation and curing conditions. The coating contains no organic volatile matter after complete ceramic conversion and offers a high level of cleanliness, reducing the risk of contaminating processed products.

These characteristics make PHPS suitable for high-purity production environments in the fine chemical industry.

3. Key Technical Parameters: From Laboratory Research to Industrial Application

Properties of the Liquid Material

• Appearance: Colorless, transparent liquid

• Density: 0.95–1.31 g/cm³

• Typical industrial solids content: 20%

Curing Options

• Complete ceramic conversion after approximately seven days of moisture curing at room temperature

• Approximately two hours of curing at 150°C under humidified conditions

• Rapid curing in approximately five minutes when used with a suitable UV light source

• Adaptable to continuous production lines

Mechanical Properties of the Film

• Hardness after high-temperature curing: 8–10 GPa

• Pencil hardness: Up to 9H

• Cross-cut adhesion: Grade 0

• Elastic modulus: 100–130 GPa

Thermal Stability

• Long-term operation at approximately 400°C in air

• Weight loss below 5% at 1,000°C under an inert atmosphere

Corrosion-Protection Performance

• Weight loss below 5% after 168 hours of immersion in a mixed medium containing acids, alkalis and organic solvents

• Dielectric breakdown strength above 30 kV/mm

• Combined electrical insulation and corrosion-protection performance

Recommended Coating Thickness

• General corrosion protection: 20–80 μm

• High-temperature and severe-corrosion environments: 50–100 μm

• Can be applied as a single integrated coating system without a separate primer and topcoat in suitable applications

Actual performance depends on the PHPS formulation, substrate preparation, film thickness, curing conditions and test method.

4. Applications Across High-End Industries

4.1 New Energy Applications

Lithium-Ion Battery Separator Coatings

The inorganic coating formed from PHPS can improve the thermal stability and puncture resistance of battery separators, contributing to improved battery safety.

Battery Pack Components and Inverter Protection

Its high-temperature resistance and electrical insulation properties can help protect electronic components used in battery packs and inverters.

Photovoltaic Module Encapsulation

Vacuum ultraviolet curing can be used to produce a film with very low water-vapor transmission. By limiting the penetration of moisture and oxygen, the coating can help extend the service life of photovoltaic modules.

4.2 Semiconductor and Electronics Applications

Wafer Insulation and Chip Passivation

After curing, PHPS forms a silicon-dioxide-based coating with favorable dielectric properties, thermal resistance and chemical stability.

In selected applications, it may provide an alternative to conventional high-temperature deposition processes, potentially reducing processing complexity and production costs.

Conformal Protection for Printed Circuit Boards

PHPS coatings can withstand the elevated temperatures associated with reflow soldering without readily decomposing, helping improve the reliability of electronic assemblies.

Flexible Electronics Encapsulation

A dense PHPS-derived barrier layer can protect flexible electronic devices against moisture, oxygen and other environmental influences.

4.3 Industrial Protection

Aerospace, Automotive and Mechanical Equipment

PHPS can be used to develop high-temperature anticorrosion and oxidation-resistant coatings for components exposed to severe thermal and environmental conditions.

Rail Transportation

Corrosion- and wear-resistant coatings can be applied to vehicle bodies and components to help extend their service life.

Anti-Graffiti Protection for Buildings

The dense, smooth surface of a cured PHPS coating makes it more difficult for graffiti materials to adhere and can simplify cleaning.

Protection of Precious Metals

PHPS coatings can help isolate precious-metal products from corrosive environments while preserving their appearance.

4.4 Additional Applications

Gas-Barrier Films

PHPS-derived films can be used in food packaging and electronic-device packaging to restrict the transmission of oxygen and water vapor.

Water- and Oil-Repellent Coatings

Modified PHPS systems can provide low surface energy and favorable water- and oil-repellent properties for self-cleaning applications.

Nanocomposite Ceramic Materials

PHPS can serve as a precursor for producing high-performance nanocomposite ceramic materials.

5. The Development of the PHPS Industry in China

High-purity PHPS raw materials were previously dominated by suppliers from Germany and Japan. High import prices and long delivery cycles restricted the wider industrial adoption of the material.

Over the past five years, the Institute of Chemistry at the Chinese Academy of Sciences and other domestic organizations have made progress in PHPS synthesis, purification and scaled production, gradually changing the structure of the industry.

General-Purpose PHPS

The localization rate of PHPS used for electronic isolation and room-temperature corrosion protection has reportedly reached approximately 90%. Production capacity has expanded, while market prices have declined significantly.

Medium- and High-End Industrial Anticorrosion Grades

Domestically produced PHPS designed for aromatic-hydrocarbon resistance and high-temperature industrial corrosion protection reportedly accounts for approximately 65% of the Chinese market.

These materials are already being supplied in volume to the new energy, semiconductor, aerospace and other advanced manufacturing sectors.

Ultra-High-Purity Semiconductor Grades

Approximately 35% of this market is still reported to depend on imported materials. Ultra-high-purity semiconductor-grade PHPS therefore remains an important development target for domestic producers.

The industry continues to have a high technical threshold because PHPS synthesis and purification are complex. Fewer than ten companies in China are currently believed to possess stable mass-production capabilities for corrosion-resistant PHPS grades.

Demand from the new energy, semiconductor and aerospace sectors continues to increase, and annual industry growth is reported to remain above 25%. Compared with conventional silicate and epoxy anticorrosion markets, PHPS still has considerable room for expansion.

6. PHPS Development Trends Over the Next Three Years

6.1 Replacement of Conventional Coatings in High-End Manufacturing

Stricter environmental protection and workplace safety standards are highlighting the disadvantages of conventional anticorrosion coatings, including limited service life and frequent maintenance.

Ultra-thin, long-lasting PHPS ceramic coatings are expected to gain wider use in equipment-upgrade projects and may become a standard supporting technology in selected high-end manufacturing applications.

6.2 Growth of Modified and Composite Formulations

Pure PHPS films can provide limited wear resistance in certain thin-film applications. To address this issue, formulators are increasingly combining PHPS with silicon carbide, aluminum oxide, mullite and other ceramic powders.

These composite coatings are designed to combine erosion resistance, corrosion protection and high-temperature stability. Application-specific formulations may also provide greater commercial value than general-purpose products.

6.3 Wider Adoption of Low-Temperature, Rapid-Curing Technologies

Traditional high-temperature curing requires substantial energy. New UV-assisted and low-temperature PHPS curing systems can achieve rapid ceramic conversion at temperatures below 120°C.

These technologies are more suitable for field application on large equipment and can reduce energy consumption associated with industrial baking and heat treatment.

6.4 Faster Localization Across the Supply Chain

Domestic manufacturers are continuing to expand high-purity raw-material capacity and reduce dependence on imported high-end anticorrosion and electronic-grade PHPS.

As production capacity increases and raw-material costs decline, PHPS is expected to move from a specialized high-end material toward broader use in heavy-duty corrosion protection.

6.5 Expansion into Multifunctional Coatings

Beyond corrosion and wear resistance, PHPS is being developed for electrical insulation, hydrogen-barrier and self-cleaning applications.

Multifunctional PHPS coatings could serve the new energy, semiconductor, aerospace and energy-storage sectors, further expanding the boundaries of the market.

7. Conclusion: PHPS Is Not a Conventional Silicone Coating

Perhydropolysilazane is an advanced precursor material used to produce inorganic ceramic films at relatively low processing temperatures. Under combined high-temperature and highly corrosive conditions, properly formulated PHPS coatings can outperform conventional epoxy, polyurethane and general silicate anticorrosion systems.

The principal limitation is that high-end corrosion-resistant PHPS raw materials remain more expensive than conventional coating materials. However, their longer maintenance intervals and ability to reduce production-line downtime may result in lower total operating and maintenance costs.

Successful application depends on selecting the appropriate film thickness, substrate-treatment process, formulation and curing method. When these conditions are properly matched, PHPS can provide a practical solution to long-term corrosion and repeated equipment maintenance.

-- Originally published by the WeChat public account “Liquid Ceramic Precursors.”