Chlorine (CL2) is a member of the halogen elements group that is highly reactive and bonds easily with hydrogen to form HCL acid. HCL attacks stainless steel aggressively – literally passivating the surface of the stainless steel, and can render a thermal mass flow controller inoperative in a brief period of time. CL2 is used frequently in many applications from making PVC pipe and treating water to plasma etching a computer chip.
