Selection of coating materials
【Analysis of the Advantages and Disadvantages of Solvent – based and Water – based Types】In the surface treatment process of fasteners, the choice of coating is a key factor affecting the coating quality, environmental impact, and production cost. With the increasing stringency of environmental protection regulations and the rising market demand for high – performance and low – pollution coatings, the coating industry has experienced a transformation from solvent – based to water – based coatings. This transformation not only conforms to the environmental protection trend but also brings sustainable development advantages to enterprises.
1. Solvent-based coatings
Solvent-based coatings mainly use organic solvents as the base, have good fluidity and coverage, and are widely used in high-demand fastener coatings. Its main advantages are as follows: Excellent coating performance: Solvent-based coatings have good fluidity, can evenly cover complex surfaces, and the coating is dense, providing strong corrosion resistance and wear resistance. High coating density: Due to the low solvent content, the structure of the coating is more compact, which can provide better environmental resistance for fasteners.
However, solvent-based coatings also have significant disadvantages: Environmental pollution: Volatile organic compounds (VOCs) in solvent-based coatings can pollute the environment and pose a potential threat to the health of operators.
High production cost: The procurement, storage, and recycling of solvents increase the production cost, and the waste caused by solvent volatilization also affects the cost. Difficulty in compliance: Many countries and regions have strict controls on VOC emissions, and enterprises using solvent-based coatings face higher compliance pressure.
2.Water-based Coating
Water-based coatings use water as the solvent, offering lower VOC emissions and higher environmental friendliness. With increasingly stringent environmental regulations, water-based coatings have gradually become the mainstream choice for fastener coating. Their advantages mainly include:
Environmental protection: Water-based coatings do not contain harmful solvents and have extremely low VOC emissions, complying with environmental regulations worldwide and meeting ever-stricter environmental standards.
Operational safety: Water-based coatings are free from volatile organic compounds, reducing fire hazards and ensuring workshop safety.
Cost advantage: The production cost of water-based coatings is relatively low. Water as a solvent is inexpensive and reduces costs related to solvent treatment and recovery.
Coating quality: Although water-based coatings have a slower drying speed, technological advancements have significantly improved their flowability and coverage, allowing them to provide relatively uniform and dense coatings.
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Of course, water-based coatings also have their limitations:
Slightly inferior coating performance: Compared with solvent-based coatings, water-based coatings generally offer slightly lower density and adhesion, and their performance under high temperatures or in special environments may not match that of solvent-based coatings.
Slower drying speed: Water-based coatings take longer to dry, which can affect production efficiency, especially on high-volume production lines where additional drying and curing equipment may be require.
3.Junhe Water-based Coatings
Junhe’s water-based zinc-aluminum micro-coating solutions have been developed and refined over more than 20 years of R&D investment and market application. With outstanding quality and stability, they have earned widespread customer recognition and have been certified by major automotive OEMs.
01 Junhe®9720
JUNHE®9720 Water-based Chromium-free Zinc-based Micro-coating Anti-corrosion Solution
JUNHE®9720 is a water-based, chromium-free zinc-based coating solution independently developed by Junhe Technology. It contains no heavy metal ions, complies with RoHS standards, and meets the requirements of China’s Environmental Protection Law for zero heavy metal emissions. This coating is suitable for anti-corrosion treatment of various fasteners and hardware components.
It offers excellent salt spray resistance and strong adhesion, making it ideal for anti-corrosion coating of fasteners and hardware parts used in the automotive, wind power, photovoltaic, high-speed rail, home appliance, and telecommunications industries.
I.Functional Features
1. Excellent Safety and Environmental Performance:
Water-based, low VOC, and free of heavy metals. Complies with standards GB24409-2020, GB30981-2020, and GB/T18178-2020, and also meets the requirements of the EU RoHS Directive and ELV Directive.
2. Superior Corrosion Resistance:
| Film thickness | Coating amount | Salt Spray Test (ISO9227/ASTM B117) |
| 12~15μm | ≥240mg/dm² | 720h and no red rust |
| 13~18μm | ≥240mg/dm² primer + one coat of Zincover®9130 topcoat | ≥1500h and no red rust (topcoat 1 – 3μm) |
3. Wide Coating Process Compatibility:
Can be applied using dip-spin, spraying, or dip-drain processes with appropriate fixtures.
4. Broad Functional Properties:
The coating withstands high temperatures up to 400°C, is hydrogen embrittlement-free, and has excellent recoatability.
5. Long Storage Stability:
After mixing components A and B, performance loss remains below 20% within 20 days of stirring at 20–25°C.
II. Technical Specifications
| Specific Gravity | 1.3~1.4g/ml | Centrifugal Speed (Ø800 mm) | 230–300 rpm |
| Solid Content | 38~40% | Working Viscosity (Zahn No. 2 Cup) | Dip: 60–80 sSpray: 30–60 s
Drain: 20–40 s |
| Fineness | ＜20μm | Preheating / Time | 120 ± 10°C / ≥10 min |
| Viscosity (Zahn No. 2 Cup) | 20~30 （A+B) | Sintering / Time | 320 ± 10°C / ≥20 min |
02 Zincover®9730
Zincover®9730 Water-based Chromium-free Zinc-based Micro-coating Anti-corrosion Solution is independently developed by Junhe Technology. This chromium-free, water-based zinc coating contains no heavy metal ions, complies with RoHS standards, and meets the requirements of China’s Environmental Protection Law for zero heavy metal emissions. It is suitable for anti-corrosion coating of various fasteners and hardware components.
This coating exhibits excellent salt spray resistance and strong adhesion, meeting the coating standards required by most automotive manufacturers for fasteners and hardware parts.
I. Functional Features
1. Excellent Safety and Environmental Performance:
Water-based, low VOC, and free of heavy metals. Complies with standards GB24409-2020, GB30981-2020, and GB/T18178-2020, and also meets the requirements of the EU RoHS and ELV Directives.
2. Superior Corrosion Resistance:
| Coating Thickness | Coating Weight | Salt Spray Test (ISO 9227 / ASTM B117) |
| 12~15μm | ≥240mg/dm² | 1000 h with no red rust |
| 13~18μm | ≥240 mg/dm² base coat + one layer of Zincover®9130 top coat | ≥1600 h with no red rust (top coat 1–3 μm) |
3. Wide Coating Process Compatibility:
Can be applied using dip-spin, spraying, or dip-drain processes with appropriate fixtures.
4. Broad Functional Properties:
The coating withstands high temperatures up to 400°C, is free from hydrogen embrittlement, and has excellent recoatability.
5. Long Storage Stability:
After mixing components A and B, performance loss remains below 20% within 20 days of stirring at 20–25°C.
II. Technical Specifications
| Specific Gravity | 1.3~1.4g/ml | Centrifugal Speed at Ø800 mm | 230–300 rpm |
| Solid Content | 38~40% | Working Viscosity (Zahn No. 2 Cup) | Dip: 60–80 sSpray: 30–60 s
Drain: 20–40 s |
| Fineness | ＜20μm | Preheating / Time | 120 ± 10°C / ≥10 min |
| Viscosity (Zahn No. 2 Cup) | 20~30 （A+B) | Sintering Time | 320 ± 10°C / ≥20 min |
*These properties may vary depending on the substrate, process, batch, and the shape of the workpiece.
03 Zincover®9130
Zincover®9130 Water-based Nano Top Coat is a new water-based functional top coat independently developed by Junhe. It contains no heavy metal ions, complies with RoHS standards, and meets the requirements of China’s Environmental Protection Law for zero heavy metal emissions.
This top coat can be applied over water-based and oil-based zinc coatings, hot-dip galvanizing, electro-galvanizing, and blackened parts. It enhances coating hardness and significantly improves salt spray resistance to over 1600 hours. It also addresses issues such as poor acid and alkali resistance, and insufficient impact resistance of base coatings.
I. Functional Features
1. Excellent Safety and Environmental Performance:
Water-based, low VOC, and free of heavy metals. Complies with standards GB24409-2020, GB30981-2020, and GB/T18178-2020, and also meets the requirements of the EU RoHS and ELV Directives.
2. Excellent Scratch Resistance:
Ceramic-like coating with outstanding scratch, sandblasting, impact, and abrasion resistance.
3. Acid and Alkali Corrosion Resistance:
The base coat + top coat system significantly enhances the salt spray resistance, acid resistance, and alkali resistance of the original base coating.
| Coating Thickness | Coating Weight | Salt Spray Test (ISO 9227 / ASTM B117) |
| 1~3μm | ≥30mg/dm² | 180 h with no red rust |
| 180 h with no red rust10~16μm | ≥240 mg/dm² base coat + one layer of Zincover®9130 top coat | 1600 h with no red rust (top coat 1–3 μm) |
4. Simple Coating Process:
Excellent coating performance with a wide process window for dip coating and spraying. Application is simple and convenient.
5. Low Coating Cost:
With a base coat thickness of 8–12 μm and a dry film thickness of 1–3 μm providing full functionality, combined with low-temperature and wide-range baking, the overall usage cost is low.
II. Technical Specifications
| Specific Gravity | 0.9~1.2g/ml | Centrifugal Speed (Ø800 mm) | 210–270 rpm |
| 210–270 rpmSolid Content | 25-35% | Working Viscosity (Zahn No. 2 Cup) | Dip: 40–60 s, Spray: 30–50 s |
| Dip: 40–60 s, Spray: 30–50 sColor | Translucent Liquid | Baking / Time | 180~300℃/20~30min |
| Viscosity (Zahn No. 2 Cup) | 50~80s | Coating Surface Hardness | ≥6H (Pencil Hardness) |
*These properties may vary depending on the substrate, process, batch, and the shape of the workpiece.
Post time: Jul-18-2025