ASTM D7095 Standard Test Method for Rapid Determination of Corrosiveness to Copper from Petroleum Products Using a Disposable Copper Foil Strip
7. Corrosion Standards
7.1 ASTM Copper Strip Corrosion Standards consist of reproductions in color of typical test strips representing increasing degrees of tarnish and corrosion, the reproductions being encased for protection in plastic and made up in the form of a plaque.
7.1.1 Keep the plastic-encased ASTM Copper Strip Corrosion Standards protected from light to avoid the possibility of fading. Inspect for fading by comparing two different plaques, one of which has been carefully protected from light (for example, new plaque). Observe both sets in diffused daylight (or equivalent) first from a point directly above and then from an angle of 45°. If any evidence of fading is observed, particularly at the left-hand end of the plaque, it is suggested that the one that is the more faded with respect to the other be discarded.
7.1.1.1 Alternatively, place a suitably sized opaque strip (for example, 20 mm (3/4 in.) black electrical tape) across the top of the colored portion of the plaque when initially purchased. At intervals remove the opaque strip and observe. When there is any evidence of fading of the exposed portion, the standards shall be replaced.
7.1.1.2 These plaques are full-color reproductions of typical strips. They have been printed on aluminum sheets by a four-color process and are encased in plastic for protection. Directions for their use are given on the reverse side of each plaque.
7.1.2 If the surface of the plastic cover shows excessive scratching, it is suggested that the plaque be replaced.
8. Samples
8.1 In accordance with Practice D4057 or Practice D4177, or both, it is particularly important that all types of fuel samples that pass a low-tarnish strip classification, be collected in clean, dark glass bottles, plastic bottles, or other suitable containers that will not affect the corrosive properties of the fuel. Avoid the use of tin-plate containers for collection of samples, since experience has shown that they can contribute to the corrosiveness of the sample.
8.2 Fill the containers as completely as possible and close them immediately after taking the sample. Adequate headspace in the container is necessary to provide room for possible thermal expansion during transport. It is recommended that volatile samples be filled between 70 % and 80 % of the container's capacity. Exercise care during sampling to protect the samples from exposure to direct sunlight or even diffused daylight. Carry out the test as soon as possible after receipt in the laboratory and immediately after opening the container.
8.3 If suspended water (that is, haze) is observed in the sample, dry by filtering a sufficient volume of sample through a medium rapid qualitative filter, into the prescribed clean, dry test tube. Carry out this operation in a darkened room or under a light-protected shield.
8.3.1 Contact of the copper foil strip with water before, during, or after completion of the test run will cause staining, making it difficult to evaluate the copper foil strips.
9. Preparation of Test Strips
9.1 Surface Preparation - To prevent possible surface contamination during preparation, do not allow fingers to come in contact with the copper foil strip. Wear disposable gloves or hold the strip in the fingers protected with ashless filter paper.
9.1.1 Using a new/unused portion of a small strip of the 400 grit scouring-pad (see Note 1) first polish the ends, then the sides of the copper foil strip giving gentle, unidirectional strokes. Next, gently and unidirectionally, scour the long axis of the copper foil strip, carrying the stroke beyond the end of the strip before reversing the direction, until both surfaces demonstrate uniform asperities (roughness). Do not polish in a circular motion.
9.1.2 Alternatively, clamp the copper foil strip in a vise to facilitate uniform polishing.
9.1.3 Wash the copper foil strip with wash-solvent (see 6.1), until it is free from metal dust and other foreign matter. Immediately immerse the prepared copper foil strip in either the test sample, or store it in the wash-solvent for future use.
