ASK NDE’s TECHNICAL EXPERTS -
NDE’s technical team receives enquiries on a daily basis that require input from a stainless steel specialist.
Below is one of the questions, with the response from our technical experts.
Q. What will be a suitable limit of chloride concentration for SAF2507 (Duplex SS Gr. 1.4410)?
A.There are many factors which determine the suitability of a grade of stainless steel for a particular application. Chloride content is only one of them.
Other factors include:
- Oxygen content of the liquid
- Is the liquid flowing or stationary
- Are there metal ions in the solution
It is important to use the correct grades of stainless steel for water with limited chloride concentration (for example: in pressure testing of pipes) because the
presence of chlorides can result in pitting and crevice corrosion.
Depending on factors mentioned above, for water which is at ambient temperature, flowing, normal oxygen content and no metal ions, the following are
considered suitable limits:
- 200 ppm for grade 1.4306 (304L)
- 500 ppm for grade 1.4404 (316L)
- 1500 ppm for Duplex SS Gr. 1.4462 (2205)
One of the biggest issues for hyrdo-testing is the length of time the water remains in the tank/pipe after the test. Generally it is recommended as a maximum
of seven days.
This would indicate that 2507 would be safe up to at least 10 000ppm chloride for the conditions queried above