LaMotte CORROSION CONTROL Test Kit User Manual
Page 5
CORROSIVITY IN DEX CAL CU LA TIONS
The Corrosivity Index (Langelier’s Saturation) is used to determine
whether a water supply will support and deposit calcium carbonate. This
deposit acts as a buffer against leaching of various metals within the
distribution system; the primary concern of which is lead.
The Corrosivity Index is figured using five basic factors: pH, calcium
hardness, total alkalinity, temperature, and total dissolved solids. The
resulting formula is used to calculate the Corrosivity Index as follows:
TF + TDSF - CF - AF = pHS
Corrosivity Index = pH - pHS
With this information a water supply operator can quickly calculate the
Corrosivity Index for any system.
pH
=
pH Factor
Read directly with pH tester
TF
=
Temperature Factor
Read temperature in °C, use Index
Calculation Chart
CF
=
Calcium Hardness Factor Titrate for calcium hardness, use
Index Calculation Chart
AF
=
Alkalinity Factor
Titrate for total Alkalinity, use
Index Calculation Chart
TDSF =
Total Dissolved Solids
Factor
Use Pocketester and Index
Calculation Chart
The Corrosivity Index should be maintained at a positive value between 0
and
+
0.5.
If the Corrosivity Index is 0, the water is perfectly balanced.
If the Corrosivity Index is negative, corrosion tendencies are predicted.
If the Corrosivity Index is positive, scale forming tendencies are predicted.
NOTE:
Use supplied worksheets for Index Calculations.
5