Type Galvalum III

The Type Galvalum III Aluminum Alloy is an Al/In/Zn alloy for use in ambient temperature seawater, produced water or marine (seabed) silts. The chemistry of this alloy is optimized for a wide range of applications where temperatures are between 7-60° Celsius (45-140° Fahrenheit), and where Chloride Ion concentration is > 12 ppt. This range covers most of the world’s tropical oceans down to 200 meters (650 ft.) water depths. Chemical composition and electrochemical performance data are provided below:

Chemical Composition (% by weight)

Iron (Fe) 0.09 max
Silicon (Si) 0.08 - 0.12
Copper (Cu) 0.006 max
Zinc (Zn) 2.0 - 6.0
Indium (In) 0.01 - 0.02
Cadmium (Cd) 0.002 max
Others (each) 0.02 max
Aluminum (Al) remainder


Open Circuit Potential (-) 1.15 V vs Cu/CuS04 sw.
Closed Circuit Potential (1) (-) 1.05 V vs Ag/AgCl sw,
Seawater Capacity @25C 1150 A-Hr/lb. (2530 A-Hr/Kg.)
Seawater Capacity @5C Variable (2)
Seabed Mud Capacity (3) 950 A-Hr/lb. (2090 A-hr/Kg.)
Seabed Mud Capacity @ 5C Variable (2)


Alloy Density 0.098 lb/in3 (2.71 gm/cm3)
Cost Ratio Normal Grade Al Sows
Raw Material & Convesion 1.00

Recommended Applications

Offshore Structures (Platforms, Pipelines, FPS, FPSO, MODU, SPAR, Subsea Structure, Risers, Wind Turbine, etc) Any Tropical Ocean < 600 fsw (180 Msw) with mean water temperature higher than 45 F (7C)
Inshore Structures (Ports, Harbors, Jetties, Wind farms, Locks, Dams, Bridges, Piers etc.) Any Body of water < 600 fsw (180 Msw) with mean water temperature higher than 45 F (7C), Chloride Ion Concentration > 12 ppt. Resistivity < 200 ohm-cm
Produced Water Vessels & Tanks Any produced brine < 140 F(60 C)(4)
Seawater Ballast Tanks Suitable for most seawater applications (5)


1 - Recommended number to use when designing CP systems.
2 - Activation can be a problem with chemistries at extremes of specification in cold water.
3 - Recommended number to use when designing CP systems for offshore pipelines using bracelet or sub bottom anode systems.
4 - Consult a CP Specialist for guidance at elevated temperatures as performance de-rating will be needed.
5 - Exercise care with variable ballast tanks as dangerous volumes of hydrogen can be generated under certain conditions.
For additional guidance in application of these alloys, contact Houston.

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