An accelerated laboratory corrosion test designed to measure the relative corrosivity of naphtha streams was developed by combining and modifying two known methods of corrosion testing. The test was developed because of the need for a rapid, highly sensitive means of measuring some relatively low corrosion rates being experienced in certain naphtha handling facilities. Test spool methods had not proved completely satisfactory for the precise analysis required.
The amount of corrosion was evaluated by measuring the change in electrical resistance of a carbon steel specimen (.001-inch shim stock) during exposure to the corrosive medium. Corrosion losses could be detected to a fraction of a microinch at any time during a test using the apparatus described without interrupting the test or using any special measuring devices or techniques. Measurable and reproducible corrosion losses were obtained in a test of six hours duration.
It was found that there was good correlation between results obtained with the resistivity test and with retractable coupons. Metal loss measurements made on retractable coupons showed catalytic naphtha to be 60 percent as corrosive as virgin naphtha whereas the electrical resistance tests showed it to be 58.2 percent as corrosive. A comparison of field and laboratory data on evaluation of an inhibitor gave comparable agreement. The electrical resistance technique thus far has been applied only to naphtha and distillate drum water drawoff streams but its use has been investigated and appears promising for other refinery streams. 2.3.5
