If your roller chains are used in environments with high humidity or salt exposure — such as marine equipment, outdoor machinery, or food processing lines — you’ll want to make sure the chains you choose have corrosion-resistant properties.
To enhance performance under harsh conditions, we use salt spray testing to verify corrosion protection and provide various anti-corrosion coatings tailored for different applications. From our experience, we will teach you how these two strategies work together to extend chain life and reduce downtime.
Why Roller Chains Need Corrosion Protection
Carbon steel roller chains offer excellent strength and wear resistance but are vulnerable in corrosive environments. Exposure to moisture, salt, chemicals, or acidic/alkaline substances can lead to:
- Accelerated wear and reduced strength: Corrosion damages the chain’s surface and structural integrity, affecting precision and load capacity.
- Shortened service life: Unprotected chains deteriorate quickly outdoors or in humid conditions.
- Higher maintenance costs: Frequent replacement or lubrication increases downtime and labor expenses.
Selecting a roller chain with corrosion protection is essential for lowering total cost of ownership (TCO).
Salt Spray Testing for Corrosion Resistance
What Is a Salt Spray Test?
The salt spray test is an accelerated corrosion test that simulates natural environmental conditions inside a sealed chamber. Salt mist is continuously sprayed onto the test specimen, and the time until corrosion appears is recorded.
Common industry standards include:
- ASTM B117 – Developed by ASTM (American Society for Testing and Materials), first used in 1919, officially standardized in 1962, and still the most widely adopted salt spray test worldwide. MCC uses this method for all testing.
- ISO 9227 – Developed by the International Organization for Standardization, widely used in Europe, with slight procedural differences from ASTM B117.
| Specification | ASTM B117 | ISO 9227 |
|---|---|---|
| Saltwater Specific Gravity | 1.024286–1.037261 @ 25°C | 1.029–1.036 @ 25°C |
| Salt Content per Liter | 53 ± 10.6 g | 50 ± 5 g |
| Conductivity of Distilled Water | Max 5.0 µS/cm @ 25°C | Max 20 µS/cm @ 25°C ± 2°C |
| Impurity Requirements | Total impurities ≤ 0.3% Halides (Br⁻, F⁻, I⁻) ≤ 0.1% Copper < 0.3 ppm No anti-caking agents | Total impurities ≤ 0.5% Cu + Ni + Pb ≤ 0.005% (50 ppm) Sodium iodide ≤ 0.1% No anti-caking agents |
| Specimen Hanging Angle | 15–30° | 15–25° |
| Salt Concentration | 5% | 5% |
| pH of Salt Solution | 6.5–7.2 | 6.5–7.2 |
| Test Temperature | 35 ± 2°C | 35 ± 2°C |
| Salt Fog Deposition Rate | 1–2 ml/hour collected on an 80 cm² surface | 1–2 ml/hour collected on an 80 cm² surface |
Salt Spray Test Method
Salt spray test equipment primarily uses a tower-type airflow spray system. Its operation is based on Bernoulli’s principle: compressed air from an external source is directed through a nozzle, creating a high-speed airflow.
This airflow passes over a brine (salt solution) feed tube, generating negative pressure that draws the salt solution up to the nozzle. The solution is atomized into a fine mist, which is then dispersed through the tower spray outlet.
The mist circulates and fills the test chamber evenly, ensuring that the surfaces of all test specimens are uniformly exposed to the salt fog environment.
(Salt Spray Test Machine)
Salt Spray Test Results
For example, our NP (Nickel-Plated) chains are tested to evaluate performance in humid or mildly corrosive environments. The results provide customers with clear data for selecting the most suitable chain coating for their application.
Anti-Corrosion Coating Options from MAXTOP
We offer a range of carbon steel roller chain coatings designed for different environments, combining high tensile strength with enhanced corrosion resistance.
CRF Coating
- Outstanding corrosion protection, resistant to extreme temperatures
- Chromium-free and free of toxic metals, compliant with RoHS, ELV, and REACH regulations
- More cost-effective than stainless steel chains while delivering superior anti-rust performance in corrosive conditions
Zinc-Nickel Coating (GN)
- Electroplated zinc-nickel alloy with a stainless-like finish
- Several times more corrosion-resistant than zinc or nickel plating
- Same strength as carbon steel chains, suitable for a wide range of applications
Mechanical Zinc Plating (MZP)
- Applied mechanically instead of electrolytic plating—no hydrogen embrittlement risk
- Free from trivalent and hexavalent chromium residues
- Good corrosion resistance and maintains the same strength as carbon steel chains
Nickel Plating (NP)
- Widely used, offering moderate corrosion protection
- Ideal for humid or mildly corrosive environments
- Same tensile strength as carbon steel chains
Comparison of Anti-Corrosion Coatings
| Coating | Key Features | Salt Spray Test (ASTM B117) | Hydrogen Embrittlement | Strength vs. Carbon Steel |
|---|---|---|---|---|
| CRF | Excellent corrosion resistance, eco-friendly | 600+ hrs | No | 5–10% lower |
| GN | High corrosion resistance, stainless-like look | 500+ hrs | No | Same |
| NP | Decorative finish, moderate resistance | ~20 hrs | No | Same |
| MZP | Mechanical application, no hexavalent chromium | 60+ hrs | No | Same |
The Right Coating for Longer Chain Life
Salt spray testing and anti-corrosion coatings are key to ensuring roller chains perform reliably in harsh environments.
By following ASTM B117 testing standards and offering multiple coating options, MCC helps customers extend chain life, reduce maintenance costs, and ensure long-term operational stability.
How to Choose the Right Chain
Selecting the right roller chain depends on your working conditions — temperature, humidity, and overall environment cleanliness. Choosing properly ensures longer service life and stable performance.
- Temperature Conditions
- High-temperature environments: Choose chains that can maintain strength and lubrication stability under heat.
- Low-temperature or refrigerated areas: Use chains designed to prevent brittleness and ensure smooth operation even in cold conditions.
- Humidity Levels
- High-humidity or wet conditions: Opt for chains with corrosion-resistant coatings or self-lubricating designs to minimize rust and wear.
- Dry or indoor environments: Standard chains can usually meet performance requirements with regular maintenance.
- Cleanliness & Contamination
- Clean environments (e.g., food, electronics, pharmaceuticals): Select clean or low-lubrication chains to prevent contamination.
- Dusty or outdoor environments: Chains with sealed or protected structures reduce contamination and extend service life.
- Maintenance & Longevity
- Difficult-to-access locations: Consider self-lubricating or long-life chains that reduce the need for frequent maintenance.
- Frequent cleaning or washdown areas: Use chains resistant to moisture and chemicals for stable operation.
- Cost & Efficiency Balance
- The best choice depends on balancing performance requirements with cost — selecting a chain that matches your operating environment without unnecessary expense.
Have chain-related needs or questions?
Feel free to contact us — our professional team and engineers are ready to help you find the most suitable solution!
