Salt Spray Test Chamber for Anti-Rust Grease (ASTM B117, ISO 9227)
A Salt Spray Test Chamber is used to evaluate the corrosion resistance of anti-rust greases, coatings, and lubricants under controlled saline conditions. The test simulates marine and high-humidity environments to assess how well a grease protects metal surfaces.
1. Test Standards
✅ ASTM B117 – Standard Practice for Salt Spray (Fog) Testing
✅ ISO 9227 – Corrosion Tests in Artificial Atmospheres
✅ GB/T 10125 – Neutral Salt Spray Test
2. Salt Spray Test Chamber – Key Features
🔹 Temperature Range: 35°C to 55°C (adjustable)
🔹 Salt Solution Concentration: 5% NaCl (for neutral salt spray)
🔹 Fog Collection Rate: 1.0 – 2.0 mL/hr per 80 cm²
🔹 Chamber Material: Corrosion-resistant PP or FRP
🔹 pH Range: 6.5 – 7.2 (neutral) or 3.1 – 3.3 (acidic)
3. Testing Procedure for Anti-Rust Grease
1️⃣ Prepare the Sample
- Apply the anti-rust grease to metal test panels.
- Ensure a uniform film thickness.
2️⃣ Prepare the Salt Solution
- Dissolve 5% sodium chloride (NaCl) in deionized water.
- Adjust pH if needed.
3️⃣ Set Up the Test Chamber
- Maintain the chamber at 35°C ± 2°C.
- Adjust spray pressure (0.7 – 1.4 bar) for fine mist.
4️⃣ Run the Test
- 24 to 500+ hours depending on grease performance.
- Inspect corrosion levels at intervals.
5️⃣ Evaluate Results
- Check for rust formation, discoloration, or coating failure.
- Compare results against ASTM B117 or ISO 9227 rating scales.
4. Recommended Equipment
🔹 Standard Salt Spray Chambers (ASTM B117 Compliant)
🔹 Cyclic Corrosion Test Chambers (ISO 9227, Advanced Testing)
🔹 Benchtop vs. Walk-in Models (for large sample testing)
Detailed Evaluation Methods for Salt Spray Test Results (ASTM B117, ISO 9227, GB/T 10125)
After conducting a salt spray test on anti-rust grease, the results must be analyzed systematically. The evaluation depends on factors like corrosion degree, coating performance, and adhesion. Below are the key evaluation methods used in ASTM B117, ISO 9227, and GB/T 10125.
1. Key Evaluation Parameters
✔ Rust Formation (%) – Measure the percentage of rusted area.
✔ Corrosion Type – Identify red rust (ferrous corrosion) or white rust (zinc/aluminum oxidation).
✔ Coating Adhesion & Degradation – Assess peeling, cracking, or blistering.
✔ Time to First Corrosion (TFC) – Record the number of hours before rust appears.
✔ Weight Loss Measurement – Weigh the metal before and after the test.
2. Evaluation Standards and Rating Systems
2.1 Rust and Corrosion Rating (ASTM D610, ISO 10289)
This method assigns a numerical rating (0–10) based on rust coverage:
| Rating | Rust Coverage (%) | Evaluation |
|---|---|---|
| 10 | <0.01% | No visible corrosion |
| 9 | 0.01 – 0.03% | Very slight rust |
| 8 | 0.03 – 0.1% | Slight rusting |
| 7 | 0.1 – 0.3% | Light rusting |
| 6 | 0.3 – 1% | Moderate rusting |
| 5 | 1 – 3% | Significant rusting |
| 4 | 3 – 10% | Heavy rusting |
| 3 | 10 – 33% | Very heavy rusting |
| 2 | 33 – 50% | Severe rusting |
| 1 | >50% | Complete rust failure |
| 0 | 100% | Total failure |
✅ Pass Criteria: Most industrial anti-rust greases require a rating of 8 or higher after a set exposure time (e.g., 100, 240, or 500 hours).
2.2 Blistering Evaluation (ASTM D714)
Blistering refers to bubbles or raised areas on the grease or coating surface. The size and frequency are classified as:
| Blister Size | Description |
|---|---|
| 10 | No blisters |
| 8 | Very small blisters |
| 6 | Small blisters |
| 4 | Medium blisters |
| 2 | Large blisters |
| 0 | Extensive blistering |
✅ Pass Criteria: A rating of 6 or higher indicates good performance.
2.3 Adhesion Failure (ASTM D3359 Crosshatch Test)
To check if the grease film or protective coating remains intact:
- Make a crosshatch cut on the sample surface.
- Apply adhesive tape and pull it off.
- Rate adhesion based on coating removal.
| Adhesion Rating | Coating Removal |
|---|---|
| 5B | No peeling |
| 4B | <5% removed |
| 3B | 5–15% removed |
| 2B | 15–35% removed |
| 1B | 35–65% removed |
| 0B | >65% removed |
✅ Pass Criteria: At least 3B or higher after the test.
2.4 Red Rust and White Rust Evaluation (ISO 9227, GB/T 10125)
- Red Rust (RR): Indicates failure of the protective grease.
- White Rust (WR): Forms on zinc/aluminum coatings but does not indicate failure.
- Pass Criteria:
- Industrial grease: RR < 5% after 100–500 hours
- Zinc-coated parts: WR allowed, but RR must be minimal
2.5 Weight Loss Measurement (ISO 9227, ASTM G1)
- Weigh metal samples before and after the test.
- Calculate the weight loss due to corrosion.
- Use this formula to determine corrosion rate:
Corrosion Rate=Weight Loss×87.6/Sample Area × Exposure Time × Density
✅ Pass Criteria: Minimal weight loss over test duration.
3. Example Test Result Interpretation
| Test | Exposure Time (hrs) | Rust Rating | Adhesion (ASTM D3359) | Blistering (ASTM D714) | Weight Loss (%) | Pass/Fail |
|---|---|---|---|---|---|---|
| Sample A (Grease 1) | 240 | 9 | 4B | 8 | 0.02% | ✅ PASS |
| Sample B (Grease 2) | 240 | 7 | 3B | 6 | 0.05% | ❌ FAIL |
| Sample C (Grease 3) | 500 | 8 | 5B | 10 | 0.01% | ✅ PASS |
4. Summary of Pass/Fail Criteria
✅ Rust Rating ≥ 8 (ASTM D610)
✅ Blistering Size ≥ 6 (ASTM D714)
✅ Adhesion ≥ 3B (ASTM D3359)
✅ Red Rust (RR) < 5% after target test hours
✅ Minimal weight loss (<0.05%)