Test Method for Corrosiveness to Copper from Petroleum Products – Copper Strip Test (ASTM D130 & ISO 2160)
The Copper Strip Corrosion Test (ASTM D130, ISO 2160) evaluates the corrosive effects of petroleum products, lubricants, and fuels on copper components. It is widely used in industries like automotive, aviation, marine, and industrial lubrication to ensure that fuels and oils do not degrade copper-based engine and fuel system parts.
1️⃣ Why Perform the Copper Strip Corrosion Test?
🔹 Prevents damage to copper-containing components (e.g., fuel injectors, bearings, heat exchangers).
🔹 Detects sulfur and reactive compounds that may cause corrosion.
🔹 Ensures compliance with industry standards for fuel, lubricant, and additive quality control.
2️⃣ Test Method – ASTM D130 / ISO 2160
🔹 Principle
✔ A polished copper strip is immersed in the petroleum product at a specified temperature for a set time.
✔ After exposure, the copper strip is removed, cleaned, and visually compared to a standardized color scale.
✔ The results classify the fuel or oil’s corrosiveness from “slight tarnish” to “severe corrosion.”
3️⃣ Test Procedure
🔹 Equipment & Materials Required
✅ Copper Strip Corrosion Bath (Capable of maintaining test temperature)
✅ Polished Copper Strip (99.9% purity, ASTM D130 standard size)
✅ Petroleum Sample (Fuel, lubricant, or hydraulic fluid)
✅ Glassware & Test Tubes (For holding copper strips and test sample)
✅ Cleaning Solutions (Mixtures of toluene, acetone, and abrasive paper for copper polishing)
✅ Reference Corrosion Standards (ASTM Copper Strip Color Chart)
🔹 Test Conditions
| Test Parameter | Standard Condition |
|---|---|
| Sample Volume | 30 – 50 mL |
| Copper Strip Size | 75 × 12.5 × 1.5 mm |
| Temperature & Time | 50°C for 3 hours (lubricants & fuels) 100°C for 3 hours (aviation fuels) 150°C for 1 hour (gear oils & high-temp fluids) |
| Evaluation Method | Visual comparison with ASTM D130 color chart |
📌 Higher temperatures accelerate corrosive reactions.
4️⃣ Interpretation of Test Results
🔹 ASTM Copper Strip Corrosion Rating Scale
| Copper Strip Rating | Description | Corrosion Severity |
|---|---|---|
| 1a | Slight tarnish, light orange | Non-corrosive ✅ |
| 1b | Darker orange, slight discoloration | Non-corrosive ✅ |
| 2a | Moderate tarnish, multicolored | Mildly corrosive ⚠️ |
| 2b | Brown, slight surface roughness | Mildly corrosive ⚠️ |
| 3a | Dark brown to black | Corrosive ❌ |
| 3b | Spots, etching, or degradation | Corrosive ❌ |
| 4a | Severe corrosion, pitting, and blackening | Highly Corrosive ❌ |
📌 Grades 1a & 1b = Acceptable for fuels & lubricants.
📌 Grades 2a & higher = Indicates presence of corrosive sulfur, requiring further investigation.
5️⃣ Industries & Applications
| Industry | Application of Copper Corrosion Test |
|---|---|
| Automotive | Evaluates corrosion in gasoline, diesel, and engine oils |
| Aviation | Ensures aviation turbine fuels meet safety standards |
| Marine & Shipping | Tests bunker fuel, marine diesel oils for corrosion risks |
| Industrial Lubrication | Assesses gear oils, hydraulic fluids, and compressor oils |
| Refineries & Fuel Additive Testing | Detects corrosive sulfur in crude oil and blended fuels |
📌 Low-sulfur fuels and lubricants must pass this test to prevent engine damage.
6️⃣ Factors Affecting Copper Corrosion Test Results
🔹 Contaminants That Increase Corrosivity
❌ Active Sulfur Compounds – Found in certain fuels, cause severe corrosion.
❌ Acidic or Oxidized Additives – Accelerates copper degradation.
❌ Water & Moisture Presence – Promotes oxidation and corrosion.
✅ How to Reduce Corrosion Risk?
- Use low-sulfur fuels & lubricants.
- Add anti-corrosion inhibitors (ZDDP, metal deactivators).
- Ensure proper filtration & moisture control in storage.
7️⃣ ASTM D130 vs. ISO 2160 – What’s the Difference?
| Standard | Primary Use | Test Procedure Differences |
|---|---|---|
| ASTM D130 | Automotive & industrial applications | Used for engine oils, fuels, and lubricants |
| ISO 2160 | Aviation & jet fuels | More stringent rating system for turbine fuels |
📌 For aviation fuels, always use ISO 2160 for stricter compliance.
Testing Concerns for Copper Strip Corrosion Test (ASTM D130 / ISO 2160)
When performing the Copper Strip Corrosion Test, several factors can impact accuracy, repeatability, and result interpretation. Below are common concerns and best practices to resolve them.
1️⃣ Common Testing Concerns & Solutions
🔹 1. Sample Contamination
✅ Concern:
- Presence of water, acids, or sulfur compounds in fuels or lubricants can cause false corrosive results.
- Improper sample handling may introduce contaminants.
✅ Solution:
- Use dry, clean glassware when preparing samples.
- Filter samples to remove solid contaminants before testing.
- Store fuel and lubricant samples in sealed, inert containers to prevent oxidation and moisture absorption.
🔹 2. Copper Strip Preparation Issues
✅ Concern:
- Poorly polished copper strips can lead to misinterpretation of corrosion results.
- Residue from previous tests or improper polishing techniques affects accuracy.
✅ Solution:
- Use fresh ASTM D130-compliant copper strips for each test.
- Polish strips carefully using silicon carbide paper, followed by toluene and acetone rinsing.
- Handle strips with tweezers (not fingers) to avoid contamination.
🔹 3. Temperature & Time Deviations
✅ Concern:
- Incorrect test bath temperature or immersion time variations can alter results.
- Temperature fluctuations lead to inconsistent corrosion reactions.
✅ Solution:
- Maintain strict temperature control (e.g., 50°C for 3 hours for lubricants, 100°C for aviation fuels).
- Use a calibrated constant temperature bath to ensure precision.
- Preheat the sample before inserting the copper strip to avoid sudden temperature shifts.
🔹 4. Poor Endpoint Detection (Visual Inspection Errors)
✅ Concern:
- Subjective interpretation of copper strip tarnish can lead to misclassification of corrosion severity.
- Differences in lighting conditions or observer experience affect result accuracy.
✅ Solution:
- Use standardized lighting conditions and a reference ASTM D130 color scale.
- Compare strips side-by-side with reference standards for consistency.
- When possible, automate evaluation using imaging or digital analysis.
🔹 5. Presence of Additives in Lubricants & Fuels
✅ Concern:
- Some lubricant additives (anti-wear, extreme pressure, detergents, ZDDP) may react with copper, leading to false corrosive readings.
- Sulfur-containing compounds (e.g., thiols, mercaptans) contribute to tarnishing.
✅ Solution:
- Analyze lubricant composition using ICP-OES or XRF spectroscopy to check sulfur content.
- Conduct additional sulfur speciation tests (ASTM D2622, ASTM D5453) for further investigation.
- Consider using alternative corrosion inhibitors in formulations.
🔹 6. Handling & Safety Concerns
✅ Concern:
- Toluene, acetone, and petroleum solvents used in the test are flammable and toxic.
- Exposure to sulfur compounds may pose health risks.
✅ Solution:
- Conduct tests in a well-ventilated fume hood.
- Wear PPE (gloves, goggles, lab coat) when handling chemicals.
- Dispose of chemical waste properly as per safety regulations.
2️⃣ Best Practices for Reliable Copper Strip Corrosion Testing
| Issue | Solution |
|---|---|
| Sample contamination | Use dry, clean glassware and store samples in sealed containers. |
| Copper strip preparation | Polish strips properly, handle with tweezers, and rinse with solvents. |
| Temperature fluctuations | Use a calibrated constant temperature bath and preheat samples. |
| Subjective visual ratings | Compare strips under standard lighting with ASTM reference charts. |
| Additive interference | Perform sulfur content analysis and cross-check with other test methods. |
| Lab safety | Work in a fume hood, wear PPE, and follow proper disposal methods. |