This project will take me a while to complete, but need suggestions to start it right.

An under seawater beacon is needed. Aiming for a carbon-magnesium cell, a DC to DC converter to bring up to about 5 Volts, a low loss capacitor to store some energy to emit a 1 second signal burst of 100mW every 5 seconds.
Alternative to the capacitor, to keep instead a lithium cell topped for operation, using the Mg-C cell only when recharging is needed.

The beacon is activated/awakened only on command and shuts off itself after 10 minutes. The commanding circuitry is not part of this thread.
The aim for a Mg-C cell is to keep it on and alive longer time, as its receiver is always on.

Question is... Would the always submerged Mg-C cell anode and cathode be consumed/eroded by seawater in periods of no current consumption ?

Question 2... From the galvanic series table, what would be the detrimental effect of holding the carbon fibers with stainless steel SS wire support as a wire brush is constructed ? I mean SS interaction with C, Mg.

1 = carbon fibers cathode
2 = twisted stainless wire SS holding them and as a contact.
Anode is magnesium rod - not shown.

 

If you intend to have the magnesium in continuous contact with sea water, I don't think it will last very long.

John