Remarks:
Phosphate/pH relationship recommended to control boiler corrosion. Different forms of phosphate consume or add caustic as the phosphate shifts to the proper form. For example, addition of monosodium phosphate consumes caustic as it reacts with caustic to form disodium phosphate in the boiler water according to the following reaction:
|
NaH2PO4 |
+ |
NaOH |
® |
Na2HPO4 |
+ |
H2O |
|
monosodium phosphate |
|
sodium hydroxide |
|
disodium phosphate |
|
water |
Conversely, addition of trisodium phosphate adds caustic, increasing boiler water pH:
|
Na3PO4 |
+ |
H2O |
® |
Na2HPO4 |
+ |
NaOH |
|
trisodium phosphate |
|
water |
|
disodium phosphate |
|
sodium hydroxide
|
