ISO 2160 Petroleum products - Corrosiveness to copper - Copper strip test
6 Samples and sampling
6.1 Unless otherwise specified, samples shall be taken according to the procedures described in ISO 3170 or ISO 3171.
6.2 Samples that are required to be tested against a "low-tarnish" strip classification shall be collected in clean, dark-glass bottles, or other suitable containers that will not affect the corrosive properties of the liquid. Appropriate plastic containers are suitable for some low-volatility products, but not for gasolines. Avoid the use of tinplate containers for samples, since they may contribute to sample corrosiveness.
6.3 Fill the container as completely as possible and close it immediately after sampling. Take care to protect the sample from direct sunlight, or even diffused daylight. Carry out the test as soon as possible after receipt, and immediately after opening the container.
6.4 If suspended water (haze) is observed in the test sample, or when filling the test tube (5.3), dry the sample by filtering a sufficient volume of it through a medium rapidity qualitative filter paper into a clean, dry test tube. Carry out this operation in a darkened room or under a light-protected shield.
NOTE - Contact of the copper strip with water before, during, or after the completion of the test period will cause staining, making it difficult to evaluate the strips.
7 Preparation of test strips
7.1 Surface preparation
Remove all surface blemishes from all six sides of the copper strip (5.1) with silicon-carbide paper or cloth (4.2.1) of such degrees of fineness as are needed to achieve the desired results efficiently. Finish with 65 µm silicon-carbide paper or cloth, removing all marks that may have been made by other grades of paper or cloth used previously. Immerse the copper strip in wash solvent (4.1). Withdraw immediately for final polishing, or store for future use.
For manual surface preparation, place a sheet of the abrasive paper or cloth on a flat surface, moisten it with the wash solvent and rub the copper strip against the paper or cloth with a rotary motion, protecting the strip from contact with the fingers with an ashless filter paper. Alternatively, prepare the surface of the copper strip by means of motor-driven machines, using appropriate grades of dry paper or cloth.
7.2 Final polishing
Remove a strip from the wash solvent. Holding it in the fingers protected by ashless filter paper, polish first the ends and then the sides with the 1 05 µm silicon-carbide powder (4.2.2) picked up from a clean glass plate with a wad of absorbent cotton (4.2.3) moistened with a drop of wash solvent. Wipe vigorously with fresh pads of absorbent cotton and subsequently handle only with forceps (5.8). Do not touch the strip with the fingers. Clamp in the vice (5.6) and polish the main surfaces with silicon-carbide powder on absorbent cotton. Rub in the direction of the long axis of the copper strip, carrying the stroke beyond the end of the strip before reversing the direction. Clean all metal dust from the strip by rubbing vigorously with clean pads of absorbent cotton until a fresh pad remains unsoiled. When the strip is clean, immediately immerse it in the prepared sample.
It is important to polish the whole surface of the strip uniformly to obtain a uniformly stained strip. If the edges show wear (surfaces elliptical), they will be likely to show more corrosion than the centre of the strip. The use of a vice will facilitate uniform polishing.
