The thing that I like about using a combo tank is that I can use mild steel anodes with no degradation. The high ph neutralizes the acidity produced at the anode that will eat anodes in a lower ph solution. I use the same strength lye solution that most people use for their lye tank, 2.5% w/w (1lb / 5 gal). It works fast and well as you can see in the picture album that I posted in referenced thread.
http://www.castironcollector.com/forum/showthread.php?t=1928
https://picasaweb.google.com/105980170291882110053/CastIron02#6138084356065412082
-Shawn
http://www.castironcollector.com/forum/showthread.php?t=1928
https://picasaweb.google.com/105980170291882110053/CastIron02#6138084356065412082
-Shawn