When designing, constructing and operating equipment that comes into contact with calcium chloride, the following items should be kept in mind.
Calcium chloride is a chloride brine that is mildly corrosive. However, if handled properly, the equipment will not be damaged or suffer from pitting.
Corrosion is an oxidative process; oxygen is a necessary prerequisite for most forms of corrosion. However, concentrated solutions of calcium chloride have low solubility of oxygen and this is highly advantageous. Indeed, the maximum corrosion rate is encountered at calcium chloride concentrations of about 2 to 6%. Concentrated brines with over 30% CaCl2 are much less corrosive. Allowing air to come into contact with calcium chloride solutions should be avoided whenever possible. Corrosion in a tank containing calcium chloride is often observed at the liquid/air interface, since the brine and air come into contact with each other at this point.
pH will heavily influence the rate of corrosion. At a low pH, the combination of hydronium ion, H+ and chloride, Cl-, ions will cause a very rapid corrosion. During storage, the pH of calcium chloride should always be kept at pH above 6.5. If a low pH is suspected, it should be measured, and a suitable base, i.e., NaOH or Ca(OH)2, should be added to increase the pH. Carbon dioxide can be absorbed from the air and neutralize the small amounts of lime normally present in the calcium chloride, which will cause the pH to drop. Therefore, air should not be allowed to circulate freely over a surface of calcium chloride. Optimum pH (minimum corrosion rate) occurs in the pH range of 8 to 9.5 for mild steel.
Temperature will affect the rate of corrosion; a higher temperature will result in faster corrosion. Hence, keeping the temperature low is beneficial. In applications where calcium chloride is used as a cooling agent, low temperatures will further increase the operating life of equipment.
Some non-metallic materials such as glass, polypropylene, PVC and polyethylene are completely resistant to degradation by calcium chloride.