sdpy,
You have asked for standard tests that test for a very non-standard occurance. I don't think you will find any in the power industry world.
However, since marine operators of steam generation equipment have to deal with the potential presence of salt water carry-over into the fresh water, there may be something in the marine, naval, or nuclear navy technical sub culture.
Are we talking just some minor salinity getting past a desalinator into the fresh water supply, or are we talking pumping pure seawater into the boiler in the place of BFW (in any significant amounts)?
If the latter, first you probably have to find out if there is any carryover at all, and if so how far the salt progressed. So if you weren't already having problems with turbine deposits - which would indicate to me that you didn't have a carryover problem - you might be OK.
If, on the other hand, you were already having problems with turbine deposits, you probably need to get a sample of the deposits to a lab soon to see if they contain salt.
At 160 MW, you surely have superheaters and possibly reheaters and some of that tubing might be SS or other alloy grades highly susceptible to SCC. You need to check there too.
What are your BFW heater's and/or condenser tubed with? If SS, then you may have a problem lurking there too.
You also may and most probably have pumps, valves and other equipment that have SS components (seals, shaft sleeves, plugs, trim, etc.) in them that would be impacted by the presence NaCl.
There may be more, but I think I've mentioned enough stuff to check to last until coffee break.
rmw