Chapter 14 - Antifreeze Agents

Abstract

This chapter discusses antifreeze agents that, when added to a water-based fluid, will reduce the freezing point of the mixture. Antifreezes are used in mechanical equipment that is environments below the freezing point of water to prevent the freezing of heat transfer fluids. There are two different types of antifreeze chemicals, namely liquids that are miscible over the full concentration range and salts which are only soluble to a certain amount. As an example, ethylene glycol (EG) forms a eutectic point with water between 65% and 80% at around –70°C, whereas pure EG will solidify at –14°C. The classic antifreeze agents in heat transfer liquids are brine solutions and alcohols. Antifreezing agents are also used in cementing jobs. They are mainly salts such as calcium chloride, magnesium chloride, sodium chloride, and soda. Calcium chloride is highly corrosive and very restricted in use. Some salts, especially potassium chloride, will affect the curing time of cement, and the latter chemical is in fact used to increase the pot life of cement. Likewise, alcohol-based freezing point depressants, such as EG, can be also included in the composition.