Sacrificial anodes
Aluminum anode alloy compositions
The Deep7 aluminum alloy was designed as an effective, offshore alloy, for use in cold, deep water environments. The low Iron (Fe) content of the alloy ensures that it activates in lower temperatures and protects the platform or pipeline it is connected to for the designed life of the cathodic protection system.
The Deep10 aluminum alloy was designed as an effective, general purpose offshore alloy, for use in tropical water environments.
Aluminum anode chemical composition
| Alloy type |  |
 |
|---|---|---|
| Iron (Fe) | 0.07 max | 0.10 max |
| Silicon (Si) | 0.10 max | 0.10 max |
| Copper (Cu) | 0.003 max | 0.006 max |
| Zinc (Zn) | 4.75 - 5.25 | 2.0 - 6.0 |
| Indium (In) | 0.015 - 0.025 | 0.01 - 0.05 |
| Titanium (Ti) | 0.025 max | 0.025 max |
| Others (each) | 0.02 max | 0.02 max |
| Aluminum (Al) | remainder | remainder |
Electrochemical properties
| Alloy type | |
|
|---|---|---|
| Open circuit potential | (-) 1.08 V vs Ag/AgCl sw. | (-) 1.08 V vs Ag/AgCl sw. |
| Closed circuit potential(1) | (-) 1.05 V vs Ag/AgCl sw, | (-) 1.05 V vs Ag/AgCl sw, |
| Seawater capacity @25C | 1100 A-Hr/lb. (2420 A-Hr/Kg.) | 1100 A-Hr/lb. (2420 A-Hr/Kg.) |
| Seawater capacity @ 5C | 1100 A-Hr/lb. (2420 A-Hr/Kg.) | Variable (2) |
| Seabed mud capacity (3) | 950 A-Hr/lb (2090 A-hr/Kg.) | 950 A-Hr/lb (2090 A-hr/Kg.) |
| Seabed mud capacity @ 5C | 950 A-Hr/lb (2090 A-hr/Kg.) | Variable (2) |
Physical properties
| Alloy type | |
|
|---|---|---|
| Alloy density | 0.098 lb/in3 (2.71 gm/cm3) | 0.098 lb/in3 (2.71 gm/cm3) |
| Cost ratio | Low Iron (Fe) Aluminum (Al) Ingot < 0.05 Fe |
Normal Grade Al Sows |
| Raw material & conversion | 1.10 | 1.00 |
Recommended applications
| Alloy type | |
|
|---|---|---|
| Offshore structures (Platforms, Pipelines, FPS, FPSO, MODU, SPAR, Subsea Structure, Risers, Wind Turbine, etc) | Any Ocean. Any Depth. Any Temperature. | 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, Any Depth, Any Temperature with Chloride Ion Concentration > 12 ppt. Resistivity < 200 ohm-cm. | 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). No improvement over Deep 10 alloy. | Any produced brine < 140 F(60 C)(4) |
| Seawater ballast tanks | Suitable for most seawater applications (5). No improvement over Deep 10 alloy. | 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, please contact Deepwater. | ||