ISO 2160 Petroleum products - Corrosiveness to copper - Copper strip test
9 Interpretation of results
9.1 Interpret the corrosiveness of the test portion in accordance with one of the classifications for the corrosion standards as listed in table 1.
9.2 When a strip is in the obvious transition state between that indicated by any two adjacent standards, judge the sample by the more tarnished standard. Should a strip appear to have a darker orange colour than standard 1b, consider the observed strip as still belonging in classification 1; however, if any evidence of red colour is observed, the observed strip belongs in classification 2.
9.3 A claret red strip in classification 2 can be mistaken for a magenta overcast on brassy strip in classification 3 if the brassy underlay of the latter is completely masked by a magenta overtone. To distinguish between the two, immerse the strip in wash solvent (4.1); the former will appear as a dark orange while the latter will not change.
9.4 To distinguish between multicoloured strips in classifications 2 and 3, place the test strip in a test tube (5.3) and bring it to a temperature of 340 °C +/- 30 °C in 4 min to 6 min with the tube lying on a hotplate. Adjust the temperature while observing a high-range distillation thermometer in a second test tube. If the strip belongs in classification 2, it will assume the colour of a silver and then a gold strip. If the strip belongs in classification 3, it will take on the appearance of a transparent black, as described in classification 4a.
9.5 Repeat the test if blemishes are observed due to fingerprints or to spots from any particles or water droplets that may have touched the test strip during the digestion period.
9.6 Repeat the test if the sharp edges along the flat faces of the strip appear to be in a classification higher than the greater portion of the strip.
NOTE - In this case, it is likely that the edges were burnished during polishing.
10 Expression of results
Report the classification number in accordance with the descriptions in table 1, together with the time and temperature of the test, in the form:
Corrosion copper strip (Xh/Y °C), Class Z
Specifications limiting the maximum tarnish level to classification 1, should not indicate "maximum", since there is no other satisfactory level reportable.
NOTE - Reporting of descriptive classifications is informative only, as these do not represent intermediate corrosion levels, merely alternative appearances for similar corrosivity. Limiting values cannot be set at one of these descriptions.
11 Precision
The test method is essentially a pass/fail procedure, and no generally acceptable method for determining precision is currently available.
12 Test report
The test report shall contain at least the following information:
a) a reference to this International Standard;
b) all details necessary for complete identification of the product tested;
c) the result of the test (see clause 10);
d) any deviation, by agreement or otherwise, from the procedure specified;
e) the date of the test.
