I have built some chillers for saltwater tanks using 3/8" 316L tubing as evaporator (direct contact with the saltwater). The tubing was bent to form coil and placed in an acrylic container. The inlet and outlet of the tubing in this container were secured using cable clamp. Today I found that one of them (built 2 months ago approx.) has a (refrigerant) leak on the 316L tubing. When I checked it, it was a terrible corrosion right on the spot where it was clamped (only one of them). Other part of the tubing which exposed to the saltwater doesn’t corrode at all, looks as if it was new. What might has caused this? While it's not happen on the other side of the clamp. For biological possibility, there might some bacteria lived on this spot and secrete something very acid that might caused this corrosion. Is it possible? Thanks in advance, Jim.

Dave, thnaks for your response. Do you have any suggestion to avoid this happen again? And why this happen only on that location? The other surface which has direct exposed to the saltwater does not show the sign of corrosion. Should I use titanium tube for this? Thanks a lot.