ASTM D1838 Test Method for Copper Strip Corrosion by Liquefied Petroleum (LP) Gases
10. Procedure
10.1 With Valve B (Fig. 1), open, place approximately 1 mL of distilled water into a clean test cylinder and swirl to moisten the walls; allow the remainder to drain from the cylinder, insert the freshly polished copper strip suspended from the hook on the dip tube making sure that the bottom of the strip is at least 6.4 mm (1/4 in.) from the bottom of the cylinder when assembled. After assembly of the apparatus, close both Valve A (Fig. 1), on closure assembly with outage tube, and Valve B.
10.2 Holding the test cylinder upright so as not to wet the copper strip with water, attach the sample source to the test cylinder Valve A (Fig. 1) by means of a short length of flexible inert hose that has been purged with the sample. Admit some sample to the cylinder by opening the valve at the sample source and then Valve A.
10.3 Close Valve A without disconnecting the test cylinder from the sample source. Invert the test cylinder and open Valve B to purge the air from the test cylinder. Return the test cylinder to the upright position and drain any residual liquid through the open Valve B. Close Valve B with the test cylinder now in its upright position, open Valve A and fill the test cylinder with the sample. When the test cylinder is full, close Valve A, the valve at the sample source, and disconnect the tubing.
10.3.1 (Warning - Provide a safe means for the disposal of vapors and liquids during this and subsequent procedures.)
10.4 As soon as the flexible inert hose is disconnected, and with the cylinder in its upright position, open Valve A slightly so that all liquid above the end of the outage tube will be removed from the test cylinder. When vapor first emerges from Valve A, close Valve A.
10.5 With minimal delay, and as soon as practical after filling and venting (described in 10.4) the test cylinder (see Note 3), immerse the test cylinder in the water bath maintained at 37.8 °C +/- 0.5 °C (100 °F +/- 1 °F). Allow the test cylinder to remain in the bath for 1 h +/- 5 min.
NOTE 3 - Any delay between preparing the test cylinder, collecting the sample, and immersing the test cylinder in the water bath gives the copper strip more time in the sample, and thus more time to potentially develop increased discoloration if corrosive species are present in the sample.
10.6 At the end of the test period remove the cylinder from the bath and, holding the cylinder in a vertical position, open the bottom valve to a suitable disposal unit (10.3.1) until all of the liquid and most of the vapor is discharged.
10.7 When only a slight pressure remains in the cylinder, disassemble immediately and compare at once the copper strip that has been exposed to the liquefied petroleum gases with the ASTM Copper Strip Corrosion Standard (ADJD0130).
10.8 Handling only with stainless steel forceps, compare the exposed strip with the ASTM Copper Strip Corrosion Standard (ADJD0130). See Section 11 for further guidance and clarification. Hold both the test strip and the standard in such a manner that light reflected from them at an angle of approximately 45° will be observed. In handling the test strip during the inspection and comparison, the danger of marking or staining can be avoided if it is inserted in a flat test tube which is then stoppered with absorbent cotton.
10.9 If the copper strip contacts the water-moistened walls of the cylinder, or water droplets are splashed onto the copper strip during sample filling, this can lead to isolated spots on the copper strip that are typically circular in nature or found along the edges of the strip, or both. The presence of these isolated spots shall be disregarded when rating the copper strip, unless the conditions in 10.9.1 are met, in which case, follow 10.9.1. Uneven patches or areas of discoloration on the copper strip are evidence of sample corrosivity.
10.9.1 If the presence or number of spots, or both, on the copper strip impacts the user's ability in any way to interpret or rate the copper strip according to the criteria in Table 1, results from the analysis shall be considered suspect and the sample analysis shall be repeated.
10.10 If the copper strip shows any appreciable discoloration, the interior of the cylinder shall be polished with steel wool and washed with wash solvent prior to using the cylinder for another test.
