Coastal Angler Magazine · Tampa Bay Edition · October 2026
It is the most common corrosion question on the dock. In the October Tampa Bay edition of Coastal Angler Magazine, Misting Monsoon Diving founder Jarrett Maryon answers it with electrochemistry instead of a calendar.
The short answer
“A zinc still bolted on is not proof of protection; the millivolt number is.”
Jarrett Maryon, Misting Monsoon Diving — Coastal Angler Magazine, October 1, 2026
A sacrificial anode is the most active metal in the galvanic cell your boat forms in seawater. It corrodes so the propeller, shaft, struts and rudder do not. How quickly it goes depends on salinity, water temperature, how much metal it protects, the condition of the bonding system, and stray current in the slip. That is why two boats in the same Tampa Bay marina can run very different anode lives and both be normal.
From the article
Underwater photos published with the Coastal Angler article. Every Misting Monsoon dive is documented the same way — photo and video of what is actually on the hull.
Key points
| Material | Capacity (per lb) | Water |
|---|---|---|
| Aluminum (indium-activated) | ~1,100 amp-hours | Salt, brackish, fresh |
| Zinc | ~368 amp-hours | Salt; can passivate in brackish |
| Magnesium | — | Fresh only |
Figures as stated in the Coastal Angler article.
Anode life calculator
The article explains why anode life follows load, not the calendar. This puts numbers to it: anode metal and weight, the bare underwater metal it protects, and conditions at the slip. The formula and the numbers behind your result are shown with it, so you can check the math.
Preferred for Florida salt and brackish water. Protects well in both.
Total of all anodes protecting the same bonded metal. A common shaft anode is about 1 lb.
Square metres of exposed bronze and stainless. Painted hull is not counted.
Replace by
—months
How this is calculated
current demand = area × current density
life = (mass × fraction consumed × capacity) ÷ demand
© 2026 Misting Monsoon Diving LLC. All rights reserved. This calculator, including its method, design, text and code, is the proprietary property of Misting Monsoon Diving LLC. It may not be copied, reproduced, adapted, embedded or published, in whole or in part, without the express written permission of Misting Monsoon Diving LLC. Permission requests: beneaththewaterline@mistingmonsoon.com.
A planning estimate, not a substitute for looking. Wear that runs well ahead of it is a stray-current signal worth chasing. Same tool as the standalone Anode Life Calculator; method follows Under the Waterline, Chapter 5.
On your boat
Misting Monsoon Diving inspects anodes on every hull-cleaning visit in Pinellas County and replaces them in the water, with no haul-out. Each visit is documented with photo and video, so you see the same condition the diver sees. See Zinc & Prop Replacement, read Zinc Anodes Explained, or get the full picture in Jarrett’s free handbook, Under the Waterline.
Media & interviews: Jarrett Maryon, PADI Advanced Master Diver & Instructor, is available for interviews on anodes, galvanic corrosion, and what happens below the waterline of a Tampa Bay boat. Reach us at 727 344 9848 or beneaththewaterline@mistingmonsoon.com.
More coverage on the In the News page.
Get your anodes checked
Hull cleaning, anode inspection and in-water replacement by a certified diver who documents every dive.