Cathodic protection of aluminium
You might want to look at this link which has a nice general discussion about cathodic protection, with an abbreviated activity series for the metals of interest in cathodic protection.  Typically, aluminum, magnesium and zinc are used as sacrificial anodes for cathodic protection.

Strictly speaking from a thermodynamic standpoint, one would suspect that magnesium would be needed to protect aluminum.  However aluminum boat manufacturers state that zinc can be used for protecting aluminum boats in salt water.  

I'm completely unfamiliar with the die casting industry, but they use Al/Zn alloys which, if affordable, may provide an interesting pedagogical component to your corrosion activity (namely, what do scientists do when the properties of the elements on the periodic table don't quite fit what we have in mind).