The plastic cap on my Autoprop was lost a couple of years ago.  I have replaced it with a zinc cap made for this prop.  The problem is that the prop zincs do not last more than 3 or 4 months before enough zinc is eaten away and a hole appears in the prop cap anode.  I have a galvanic isolator and my rudder zincs loose about one-third or one-quarter of their  mass a year.  So why does the prop anode/cap do so poorly since it is not tied to the bonding system? Should I be concerned?

Mark Pitt, Sabbatical III, ASM#419, Porto Vecchio, Corsica