# Clarifying question about chloride ions, water softening & corrosion

I have a question regarding the use of NaCl as a water softener.

Recently i was asked to comment on a series of test results from a water softening device were a lot of corrosion had occurred post softening. Just to be sure we are on the same page, NaCl was added to the water to dissolve* the CaCO3, Ca(CO3)2 & CaSO4.

*Ion exchange is not my field of expertise, so I'm not quite sure if this is the correct wording

Now, according to the folks who ran the test, there were no signs of ‘Chlorides’ in the water sample, what they mean by this is still unclear. I was also informed that no precipitate was collected. Now to the actual question: they wanted to know why the pipes used, post softening, had crevice corrosion inside the pipe. My first intuition was that there were still $$Cl^-$$ ions in the water which is causing the steel to corrode. However, the folks running the test assured me that the chloride had bonded with the calcium ions.

I’ve been trying to figure out what in the world could cause the pipes to corrode, assuming that they are correct, and the chloride have formed CaCl2.

Have you guys got any ideas? Have I misted something, or am i right to assume that the folks who ran the test don't know what they are talking about.

If you need any more information, feel free to ask. As stated earlier, this is not my field of expertise so if I'm wrong about something please correct me.