In the fields of heavy anti-corrosion and high-temperature resistance, silicate-based coatings have long held an irreplaceable position due to their "inorganic film formation and chemical bonding" characteristics. Unlike organic coatings that rely on physical adhesion, they react chemically with the steel substrate to form a strong bond, thus remaining stable under extreme conditions such as high temperature, strong UV, and severe corrosion where organic coatings tend to fail. With the maturity of water-based technology, water-based silicate coatings retain the advantages of inorganic coatings while elevating construction safety and environmental friendliness to a new level, becoming an important choice for the protection of substrates such as bridges, ships, storage tanks, and high-temperature pipelines.
I. Film Formation Principle of Silicate Coatings
Silicate coatings use potassium silicate, sodium silicate, or alkyl silicates (such as ethyl silicate) as the base material. After application, the silicate undergoes a condensation reaction with the active hydroxyl groups on the substrate surface, forming an Si—O—Me (Me being metal or silicon) inorganic network that produces a bond with the steel substrate almost like "chemical welding." This chemical bonding is the fundamental reason why the adhesion of inorganic coatings far exceeds that of ordinary organic coatings. The water-based system uses water as the dispersion medium, reducing flammability and occupational health risks, and also better meets green construction requirements.
II. Water-Based Silicate and Inorganic Zinc-Rich Primer
Mixing zinc powder into a water-based silicate base yields a water-based inorganic zinc-rich primer. It combines two anti-corrosion mechanisms:
- Cathodic protection: Zinc is more active than iron and is sacrificed preferentially in the corrosion cell; even if the paint film is locally damaged, the zinc continues to protect the exposed steel substrate.
- Barrier sealing: The corrosion products of zinc (such as basic zinc carbonate) densely fill the pores and become even denser over service time, blocking the intrusion of corrosive media.
This is why the Inorganic Zinc-Rich Primer TDS performs excellently in harsh environments, and is also the core value of the water-based silicate system.
III. Reference for Key Technical Parameters
| Item | Typical Indicator | Description |
|---|---|---|
| Zinc powder content | ≥ 80% (dry film) | Inorganic zinc-rich primer |
| Temperature resistance | ≤ 400℃ long-term | Short-term may be higher |
| Salt spray resistance | ≥ 1000 h | Single zinc-rich layer |
| Dry film thickness | 60–80 μm | Single coat |
| VOC content | Extremely low | Inorganic water-based system |
| Surface dry | 15–30 min | Depends on humidity |
IV. High-Temperature and Fire-Resistant Properties
The inorganic silicate network can withstand temperatures of several hundred degrees Celsius, and can even endure higher thermal shock for short periods, without carbonizing, peeling, or blistering and failing like organic coatings. This property makes it particularly suitable for the following scenarios:
- High-temperature equipment: Exhaust pipes, chimneys, and heat exchange equipment (see high-temperature coating).
- Fireproof systems: Cable fireproofing and tunnel fireproofing systems (see cable fire-retardant coating and intumescent fire-retardant coating).
- Petrochemical piping and storage: Bottom-layer protection for external walls of high-temperature pipelines and storage tanks.
V. Environmental and Compliance Advantages
Under the context of the new GB 30981 national standard (implemented on 2026-06-01), water-based silicate coatings have extremely low VOC and contain no or little organic solvent, making it easier to meet the hazardous substance limits for industrial protective coatings, and also better aligned with the industry trend of "water-based rate 60%+". For export projects and green building projects, inorganic water-based systems have greater advantages in passing environmental assessment and certification.
VI. Construction and Substrate Requirements
- Sandblasting treatment: Must reach Sa 2.5 grade or above, with clean and oil-free surface, to ensure chemical bonding between silicate and substrate.
- Curing environment: Relative humidity is recommended at 50%–80%; appropriate humidity helps silicate hydrolysis and condensation; too low humidity requires atomized humidification to promote curing.
- Topcoat compatibility: Above the zinc-rich base layer, an epoxy micaceous iron intermediate coat or weather-resistant topcoat should be applied for sealing, to avoid white rust and powdering of the zinc layer.
- Technical parameters: Subject to the WS Water-Based Silicate TDS and Construction Guide.
VII. Frequently Asked Questions (FAQ)
Q: Why does inorganic zinc-rich primer need a topcoat? Pure zinc layer exposed to humid environments will develop white rust and gradually powder; applying an epoxy intermediate coat and weather-resistant topcoat can seal the zinc layer, delay white rust, and provide decoration and weather resistance, forming a complete system.
Q: Can water-based silicate be applied directly over old paint? Not recommended. It relies on chemical bonding with clean steel substrate for film formation, and old paint and rust must be completely sandblasted to Sa2.5 grade to perform; application over old paint will lead to adhesion failure.
Q: How high a temperature can it actually resist? Inorganic silicate zinc-rich systems can generally withstand about 400℃ long-term, with higher short-term thermal shock; the specific temperature rating should be selected according to the product specification sheet for the corresponding model.
Further Reading
- Water-Based Micaceous Iron Oxide Coating: Water-Based Long-Term Protection for Heavy Anti-Corrosion Steel Structures
- Heavy Anti-Corrosion Coating System: Complete Compatibility from Primer to Topcoat
- Heavy Anti-Corrosion Coating Market 2026: Marine and Wind Power Drive Growth
- Product Center: WS Water-Based Silicate