Crevice magnesium alloys

Crevice corrosion is often observed in clearances between metals and in places of loose contact between the metal and dielectric (including corrosion resistant materials). Passivating materials and alloys, such as stainless chromium and nickel-chromium steels, aluminum and magnesium alloys are most inclined to crevice corrosion [2,12,13]. 

Crevice corrosion does not occur with magnesium alloys because magnesium corrosion is relatively insensitive to differences in oxygen concentration (Makar and Kruger, 1993). 

Crevices in Waters In most fiesh waters crevice corrosion of aluminum is negligible. In seawater, crevice corrosion takes the form of pitting, and the rate is low. Resistance to crevice corrosion has been found to parallel resistance to pitting corrosion in seawater and is higher for aluminum-magnesium alloys than for alu-minum-magnesium-silicon alloys (Ref 14). 

The resistance to crevice corrosion of the duplexes is superior to the resistance of the 300-series austenitics. They also provide an appreciably greater resistance to SCC. Like 20Cb3, the duplexes are resistant to chloride see in chloride-containing process streams and cooling water. However, under very severe conditions, such as boiling magnesium chloride, the duplexes will crack, as will alloy 20eb3. 

Rosenfeld also studied the influence of aluminum idloy on the rate of crevice corrosion and obtained the results plotted in Fig. 5. Aluminum-coppo and aluminum-zinc-magnesium-copper idloys coroded many times fasto than 1100, Sxxx, or Sxxc alloys. Again, crevice gap width is important, because corrosion rates are low for crevice openings gieato than 2S4 pm (10 mils). 

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