⛽ Copper strip corrosion
Assessment of the corrosiveness of petroleum products and fuels towards copper by immersing a polished copper strip in the sample at elevated temperature and comparing with ASTM corrosion standards.
Overview
Copper strip corrosion test is one of the most important quality tests used in the petroleum industry to evaluate the chemical aggressiveness of fuels and petroleum products towards copper and its alloys. The presence of sulfur compounds, acids and other corrosive substances in fuels can cause damage to fuel system components made of copper and brass — pumps, lines, injectors and tanks.
The method involves immersing a polished electrolytic copper strip (purity >99.9%) in the petroleum product under test and heating at a specified temperature for a given time. After exposure, the strip is removed, washed and visually compared with ASTM corrosion standards on a scale of 1–4. Class 1 indicates slight tarnish, class 4 — severe corrosion with dark deposit.
According to quality standard requirements PN-EN 228 (gasoline), PN-EN 590 (diesel fuel) and PN-EN 14214 (FAME), the permissible copper corrosion class at 50°C is 1. Exceeding this limit disqualifies the fuel from commercial circulation. The test is mandatory for every batch of fuel introduced to the market.
The method has wide application — from quality control of automotive and aviation fuels, through evaluation of lubricating oils and solvents, to testing of crude petroleum. It is routinely used in refinery laboratories, fuel depots and independent accredited laboratories.
Method principle
A polished copper strip (70 mm × 12.5 mm × 3 mm) is immersed in 30 mL of the petroleum product under test in a glass tube or pressure bomb. The sample is heated in a thermostatic bath to a specified temperature (typically 50°C or 100°C) for 3 hours (or other time depending on product type). Sulfur compounds, acids and other corrosive substances present in the product react with the copper surface, causing tarnishing or corrosion. After exposure, the strip is washed with acetone, dried and visually compared with ASTM corrosion standards, classifying the result on a scale from 1a (slight tarnish) to 4c (black corrosion).
Applications
- Quality control of unleaded gasoline (PN-EN 228) — class 1 at 50°C
- Diesel fuel testing (PN-EN 590) — class 1 at 50°C
- FAME / biodiesel evaluation (PN-EN 14214)
- Aviation fuel control (Jet A-1) — class 1 at 100°C in pressure bomb
- Testing of lubricating oils, greases and petroleum solvents
- LPG corrosiveness assessment (PN-EN 15779, 40°C)
- Quality monitoring of fuels at storage depots and fuel stations
Key parameters
| Parameter | Value |
|---|---|
| Test temperature | 50°C (automotive fuels) or 100°C (aviation fuels, oils) |
| Exposure time | 3 h (typical), 2 h (aviation fuels in bomb) |
| Rating scale | 1a–4c (16 degrees of ASTM standards) |
| Strip dimensions | 70 × 12.5 × 3 mm, electrolytic copper >99.9% |
| Sample volume | 30 mL in glass tube |
| PN-EN 590/228 requirement | Class 1 (maximum) |
Standard
- Standard number
- PN-EN ISO 2160:2004
- Title (PL)
- Przetwory naftowe — Korozyjność dla miedzi — Próba na płytce miedzianej
- Title (EN)
- Petroleum products — Corrosiveness to copper — Copper strip test
Step-by-step procedure
1. Copper strip preparation
Polish the strip with SiC abrasive paper P150, then P240, rubbing along the long axis. Remove metal dust with clean cotton wool soaked in acetone.
2. Visual inspection of strip
Check that the surface is uniformly shiny, without scratches, stains and discoloration. Do not touch the surface with bare fingers.
3. Sample preparation
Measure 30 mL of petroleum product under test into a clean, dry glass tube. For volatile samples use pressure bomb.
4. Strip immersion
Place the polished strip in the tube with sample so that it is completely immersed. Close the tube with stopper or pressure bomb.
5. Heating in bath
Place the tube in thermostatic bath heated to required temperature (50°C for diesel/gasoline, 100°C for aviation fuels). Maintain temperature ±1°C.
6. Strip removal
After exposure time, remove tube from bath. Carefully extract strip with non-metallic tongs.
7. Washing and drying
Immediately wash strip with acetone or isooctane. Dry with clean filter paper — do not rub the surface.
8. Visual evaluation
Compare strip color with ASTM corrosion standards under good daylight or equivalent illumination. Assign class from 1a to 4c.
9. Result recording
Record corrosion class (e.g., "1a — slight tarnish"). For commercial fuels required class 1 (1a or 1b).
10. Equipment cleaning
Rinse tubes with toluene, then acetone. Dry. Dispose of used copper strips for metal recycling.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Copper corrosion bath | Koehler K25330/K25339, Stanhope-Seta 11300-2, Tamson TV 2000 | 15 000–35 000 PLN |
| Pressure bomb (aviation fuels) | Koehler K25308, Stanhope-Seta 11310-0 | 8 000–15 000 PLN |
| ASTM corrosion standards (Copper Strip Corrosion Standards) | Set of standards 1a–4c, ASTM certified | 3 000–6 000 PLN |
| Copper strips for testing | Cu >99.9%, 70×12.5×3 mm, Inkom Instruments | 300–600 PLN / 50 pcs. |
| SiC abrasive paper and cotton wool | SiC P150/P240, cotton for polishing | 50–150 PLN |
| Glass tubes with stoppers | Tubes 25×150 mm borosilicate | 20–50 PLN/pc. |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Acetone | 67-64-1 | Analytical grade, for washing strips before and after test |
| Isooctane (2,2,4-trimethylpentane) | 540-84-1 | Reference solvent for rinsing volatile samples |
| Toluene | 108-88-3 | For washing tubes and equipment, analytical grade |
| Silicon carbide abrasive paper | 409-21-2 | Granulation P150 and P240, for polishing copper strips |
Health and safety (OHS)
- Acetone, toluene — flammable, work under fume hood, away from ignition sources
- Fuel samples — flammable and volatile, use nitrile gloves and safety glasses
- Thermostatic bath — burn risk (50–100°C), use heat-resistant gloves
- Pressure bomb — cool to room temperature before opening
- Ventilation — ensure good ventilation of test area