Gypsum scale control by phosphate ester

Calcium sulphate dihydrate (gypsum) scale has been prevented at temperatures ranging from 40¯90°C using organic phosphate ester as a scale inhibitor. The amount of scale deposited increases as temperature and time increase. The influence of phosphate ester on scale deposition clearly shows that the dose required for inhibition is small at low temperature and increases with a rise in temperature. The relationship between the time of the test and amount of scale deposited at the same temperature and concentration of the inhibitor are discussed. Gypsum has been inhibited through threshold inhibition as well as stabilization by adsorption onto crystal growth sites of nascent crystals altering their morphology.