Table 2. Continued 



Parameter 



Influence 



Effect on the Reaction 



Hydrogen gas 



Cell internal 



Gas bubbles displace 



volume in 



resistance; elec- 



electrolyte from con- 



electrolyte 



trolyte circulation 



tact with the anode, 

 reducing reaction rate. 

 (The effect of the gas 

 is particularly evident 

 near the top of the 

 cell where there is the 

 largest proportion of 

 gas bubbles. After the 

 anodes have reacted for 

 some time, they are 

 tapered, with the thick- 

 est portion being at 

 the top . ) 



Anode compo- 



Reaction product 



Pure magnesium produces 



sition 



consistency 



a fluffy product that 

 easily clogs the elec- 

 t ode gap (decreases 

 reaction rate). AZ- 

 31B-0 or AZ-31B-H24 

 magnesium alloy produces 

 a product that readily 

 precipitates (does not 

 slow reaction rate 

 except after much pre- 

 cipitation has accumu- 

 lated) . Other anode 

 compositions have been 

 investigated, but AZ31B 

 was selected on the 

 basis of availability, 

 performance, low cost, 

 and lack of pollutants, 

 such as Hg. 



Cathode 



Unknown 



Iron cathodes produce 



composition 





a reasonable reaction 

 rate; other cathodes 

 produce significantly 

 lower rates. 



continued 



53 



