Multiple crevice assembly

EPDM Ethylene propylene elastomer MCA Multiple crevice assembly... 

To overcome these limitations. Method D measures the critical crevice corrosion temperature, using a multiple crevice assembly (MCA). The test solution is 6 wt. percent FeCl3 acidified with 1 wt. percent HCl. This test method is also referenced in ASTM G 157 for evaluating the corrosion properties of wrought iron- and nickel-based corrosion resistant alloys for the chemical process industries. 

The multiple crevice assembly (MCA) consists of two "serrated washers made of TFE-fluorocarbon bolted together through a hole drilled in the specimen, as illustrated in Fig. 2(b). The bolts, made of a highly corrosion resistant alloy, are electrically isolated from the specimen. The MCA eliminates the crevices created where the rubber band contacts the specimen and facilitates the measurement of the crevice area to boldly exposed area ratio. The advantage of the MCA is that the crevice geometry can be made very severe by... 

FIG. 2—Standardized crevice corrosion test specimen assemblies described in ASTM G 48 B (top) [25,44] and ASTM G 78 (bottom) [78,79], commonly referred to as the rubber band assembly and multiple crevice assembly (MCA), respectively. 

Kain, R. M., Crevice Corrosion Testing in Natural Seawater Significance and Use of Multiple Crevice Assemblies, Journal ofTestingandEvaluation, Vol. 18, No. 5,1990, pp. 309-318. 

ASTM G 78, Guide for Crevice Corrosion Testing of Iron Base and Nickel Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environment, descrihes the use of multiple crevice assemblies and other devices applicable to nickel alloy testing in chloride environments. These procedures can be used to identify conditions most likely to result in crevice corrosion and provide a basis for assessing the relative resistance of various alloys to crevice corrosion under certain specified conditions. 

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