The Corrosivity of Magnesium Alloys in 5 and 20 Percent Salt Fog Environments

摘要

The report presents the results and analysis of a factorial experiment undertaken to determine the corrosivity of variously protected magnesium alloys when exposed to 5 and 20 percent salt fog environments. The investigation considers two lots of magnesium sand castings and one lot of magnesium sheet alloy, each given two preparatory chemical pretreatments and coated with three different batches of a thermosetting epoxy resin coating using two methods of application. For cast magnesium alloy, corrosion was noted to vary widely within and between the alloy lots investigated and their pretreatments. The relative corrosivity of the exposure environments on the alloy lots was found to depend upon the pretreatment used. For the more corrosion resistant pretreatment, 20 percent salt fog was substantially more corrosive than 5 percent. For the less effective pretreatment, no significant difference in the corrosivity of the two salt fog environments was apparent. For sheet magnesium alloy, corrosion was significantly less extensive and less variable than for cast alloy in both exposure environments. Regardless of the pretreatments, coatings used, and methods of application, 20 percent salt fog was found substantially more corrosive than 5 percent. (Author)