Spring Material: Tantalum
Tantalum is the only material that withstands chlorine acid directly.
Grades / Attributes
Tantalum 61 is used for springs for valve applications.
Tantalum springs are used in municipal processing plant valves for water and sewer lines because they can withstand direct contact with chlorine which is used in the waste water purification. Also used in the electronic industry for contacts.
Superior properties when compared to Hastelloy C. Chlorine concentration levels will determine if Hastelloy is suitable for sewage treatment applications or if an upgrade to Tantalum is required.
It is extremely expensive, ranging from $800 to $1,500 per pound. It is also not very strong, so unless you have continual exposure to high concentrations of chlorine, you are likely to consider alternatives.