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The American Water Works Association (AWWA) developed a numerical soil corrosivity scale, applicable to cast iron alloys. The severity ranking by assigning points for different variables. When the points total of a soil in the AWWA scale equals ten (or higher), corrosion protective measures (such as cathodic protection) have been recommended for cast iron alloys. The point system for predicting soil corrosivity according the AWWA C-105 Standard.
Soil Parameter | Assigned Points |
Resistivity (ohm cm) | |
<700 | 10 |
700 - 1000 | 8 |
1000 - 1200 | 5 |
1200 - 1500 | 2 |
1500 - 2000 | 1 |
> 2000 | 0 |
0-2 | 5 |
2-4 | 3 |
4-6.5 | 0 |
6.5-7.5 | 0 |
7.5-8.5 | 0 |
>8.5 | 3 |
Redox Potential (mV) | |
>100 | 0 |
50-100 | 3.5 |
0-50 | 4 |
<0 | 5 |
Sulfides | |
Positive | 3.5 |
Trace | 2 |
Negative | 0 |
Moisture | |
Poor drainage continuously wet | 2 |
Fair drainage generally moist | 1 |
Good drainage generally dry | 0 |
