ABOUT HARBOR ISLAND SUPPLY
Harbor Island Supply is a third generation family owned casting facility that operates out of a 23,000 square foot plant, and has been manufacturing and distributing Zinc, Magnesium and Aluminum anodes for cathodic protection since 1981.
“HARBOR” anodes are produced to the latest military specifications with virgin, high-purity metals before adding controlled amount of additives for the alloys to insure quality. For maximum current output, proper bonding between the anode and the core must exist. Casting temperatures are computer controlled and cores are prepped to enable this bonding.
No production run is too large or small, and our in-house machine shop allows us the ability to design and build molds for quick lead times for custom or special orders. We can help with anode design to fit a particular application, and can make suggestions to alter some designs for economical reasons to the end user.
Anodes: Zinc, Aluminum & Magnesium
The three main metal alloys used as galvanic anodes are Zinc, Aluminum and Magnesium. Each alloy has both advantages and disadvantages, dependant on many variable situations. Care should be taken to determine which type of anode is installed
Magnesium has the most negative electro potential of the three and is more suitable for areas where the electrolyte (soil or water) resistivity is higher. This is usually on-shore pipelines and other buried structures, although it is also used on boats in fresh water and in water heaters.
Zinc is considered a reliable material, but is not suitable for use at higher temperatures, as it tends to passivate (becomes less negative); if this happens, current may cease to flow and the anode stops working. Zinc has a relatively low driving voltage, which means in higher-resistivity soils or water it may not be able to provide sufficient current.
Aluminum anodes have several advantages, such as a lighter weight, and much higher capacity than zinc. However, their electrochemical behavior is not considered as reliable as zinc, and greater care must be taken in how they are used.
Zinc and Aluminum are generally used in salt water, where the resistivity is generally lower. Typical uses are for the hulls of ships and boats, offshore pipelines and production platforms, in salt-water-cooled marine engines, on small boat propellers and rudders, and for the internal surface of storage tanks.