Where you at, Pete?
Even though Zinc & Aluminum
are very close on the galvanic series, I generally wouldn’t mix anode types, as the less noble Zinc (anodic) may corrode to protect the more noble Aluminum (cathodic) metal.
This has likely been happening, if you find the Zinc anodes eroding more quickly than the Aluminum.
Pure zinc has a theoretical capacity of 372 Ampere Hours per pound. That means at 1 amp,it would take 372 Hours to consume a pound of zinc. Now,zinc operates at about 95% efficiency so it would actually be approx.
On a steel hull
, the current
requirements for protection (to about -800 to -1050 mv) could be between .3 ma (milliamp) and 6 ma. per sq. ft. for submerged protection, depending on coating quality or lack thereof and very little water
So, for example, a 25lbs zinc anode, putting out 2 amps would last approx. (25lbs x 353 amphrs/ 2 amps/24hrs) or
8825/2= 4412.5/24= 183.8 days.
Keep in mind that this is all theoretical and has many variables
Anodes should be replaced at about 50% erosion.