⛽ Copper strip corrosion

Petrochemistry PN-EN ISO 2160

Overview

STATUS (as of 30.10.2026). PN-EN ISO 2160:2004 — Polish version, published 13.04.2004, implements EN ISO 2160:1998 and ISO 2160:1998 [IDT]; it replaced PN-EN ISO 2160:2002 (English version). The PKN catalogue card has no withdrawal note and no “Replaced by” field — the standard is current. ISO 2160:1998 (third edition, replaced ISO 2160:1985) is the current ISO edition.

SCOPE (clause 1). Method for determining the corrosiveness to copper of liquid petroleum products and certain solvents, including volatile products with a vapour pressure of up to 124 kPa at 37.8 °C. Products with a higher vapour pressure are tested according to ISO 6251, and electrical insulating oils according to ISO 5662. The standard warns that some products, particularly natural gasolines, may have a vapour pressure markedly higher than is characteristic of their class: a pressure vessel containing such a product is not placed in a bath at 100 °C, because the pressure may rupture it.

TEST CONDITIONS (8.1). Time and temperature depend on the class of product: aviation fuels are tested in a pressure vessel at 100 °C, natural gasolines at 40 °C, and other liquid products in a test tube at 50 °C, 100 °C or a higher temperature; other conditions may be set by specifications or by agreement between the parties. The standard does not give a single test duration — it is set by the product specification.

RESULT (clauses 9–11, Table 1). The appearance of the strip is assigned to the classification of the corrosion standards: 1 — slight tarnish (a, b), 2 — moderate tarnish (a–e), 3 — dark tarnish (a, b), 4 — corrosion (a–c). The result is reported as the classification number together with the test time and temperature, in the form “Corrosion copper strip (X h/Y °C), Class Z”; the letter descriptions are informative only and do not represent intermediate levels. The test is essentially a pass/fail procedure — there is no generally accepted method for determining its precision. Specifications limiting the result to classification 1 should not state “maximum”, because no other satisfactory level is reportable (clause 10).

LEGAL REQUIREMENTS. Motor petrols and diesel fuel: copper strip corrosion test (3 h at 50 °C) — class 1 (Regulation of the Minister of Climate and Environment of 26.06.2024 on quality requirements for liquid fuels, Journal of Laws 2024, item 1018: Annexes 1 and 2 item 9, Annex 3 item 12). Methyl ester used as a stand-alone fuel (B100): class 1 in the 3 h test at 50 °C (Journal of Laws 2025, item 426, Annex 1 item 6).

WHAT WE DO NOT GIVE HERE. The publicly available text of the standard covers clauses 1–12 with Table 1; outside it are the informative Annexes A and B (among other things, the composition and maintenance of the corrosion standards) — we do not give those details. The American method ASTM D130 on the same subject explains that some of the sulfur compounds remaining in a product after refining can have a corroding action on metals, and that this corrosivity is not directly related to the total sulfur content.

Method principle

A polished copper strip is immersed in a specified volume of sample (30 ml) and heated under time and temperature conditions specific to the class of product being tested. Aviation fuels and natural gasolines are tested in a test tube placed in a pressure vessel, other products in a test tube at atmospheric pressure. At the end of the heating period the strip is removed, washed with solvent and its colour is assessed by comparison with corrosion standards (clause 3).

Applications

• Motor petrols and diesel fuel — class 1 in the 3 h test at 50 °C (Journal of Laws 2024, item 1018)
• Methyl ester used as a stand-alone fuel (B100) — class 1 in the 3 h test at 50 °C (Journal of Laws 2025, item 426, Annex 1)
• Aviation fuels — test in a pressure vessel at 100 °C (8.1)
• Natural gasolines — test at 40 °C (8.1)
• Other liquid petroleum products and certain solvents with a vapour pressure of up to 124 kPa at 37.8 °C (clause 1)

Key parameters

Standard

Standard number

PN-EN ISO 2160:2004

Title (PL)

Przetwory naftowe — Korodujące działanie na miedź — Badanie na płytce miedzianej

Title (EN)

Petroleum products — Corrosiveness to copper — Copper strip test

Step-by-step procedure

1. Sampling and storage

   The sample is taken according to ISO 3170 or ISO 3171. When the result is to be compared with a low-tarnish classification, clean dark-glass bottles or other suitable containers are used — not tinplate, and plastic containers are not used for gasolines. The container is filled as completely as possible, protected from light, and the test is carried out as soon as possible, immediately after opening the container (clause 6).

2. Removing water from the sample

   If suspended water (haze) is visible, the sample is dried by filtering it through a medium-rapidity qualitative filter paper into a clean, dry test tube, in a darkened room or under a light-protected shield (6.4).

3. Surface preparation of the strip

   Blemishes are removed from all six sides of the strip with silicon-carbide paper or cloth, finishing with the 65 µm grade; the strip is immersed in the wash solvent and polished at once or stored for later use (7.1).

4. Final polishing

   Holding the strip through ashless filter paper, it is polished with 105 µm silicon-carbide powder on cotton moistened with solvent — first the ends and sides, then, clamped in the vice, the main surfaces along the long axis. Metal dust is removed with clean cotton until a fresh pad remains unsoiled; from then on the strip is handled only with forceps and immediately immersed in the sample (7.2).

5. Immersing the strip

   A 30 ml test portion, clear and free of suspended water, is placed in a clean, dry test tube, and the strip is slid in within 1 min of completing the polishing. The tube is closed with a vented cork; for aviation fuels and natural gasolines the tube is slid into the pressure vessel and the lid is screwed on tight (8.2–8.3).

6. Heating

   The pressure vessel is completely immersed in the liquid bath, and the test tube placed in the bath, at the test temperature ± 1 °C, for the period required by the specification ± 5 min. After removal, the pressure vessel is immersed in cool water for a few minutes before it is opened. If the liquid level in the tube has fallen below the strip, the test is repeated with a 35 ml test portion (8.2–8.3).

   🌡 Temperature: 40 °C, 50 °C, 100 °C or higher — according to the class of product

7. Removing and washing the strip

   The contents of the tube are emptied into a beaker (e.g. a 150 ml tall-form beaker), letting the strip slide in gently; the strip is immediately withdrawn with forceps, immersed in the wash solvent, withdrawn and dried with quantitative filter paper by blotting, not wiping (8.4).

8. Assessment

   The strip is compared with the corrosion standards, holding both so that light reflected at an angle of about 45° is observed. A transition state between two standards is judged by the more tarnished one; a strip darker orange than standard 1b still belongs to class 1, but any red colour means class 2. The tests in 9.3–9.4 are used to distinguish classes 2 and 3 (8.4, 9.1–9.4).

9. Repeating the test

   The test is repeated if the strip shows fingerprints, marks of particles or water droplets, or if the sharp edges of the strip appear to be in a higher class than most of the strip (9.5–9.6).

10. Result and report

    The classification number from Table 1 is reported together with the test time and temperature, e.g. “Corrosion copper strip (3 h/50 °C), Class 1”; the report also gives the reference to the standard, identification of the product, any deviations and the date of the test (clauses 10, 12).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard warns that its use may involve hazardous materials, operations and equipment, and that the user establishes the safety and health practices (warning before clause 1)
• A pressure vessel containing natural gasoline is not placed in a 100 °C bath — it may rupture (clause 1)
• Before opening, the pressure vessel is cooled for a few minutes in cool water (8.2)
• Fuel samples and the wash solvent are handled according to their safety data sheets

Frequently asked questions