The latest thing that I have learned is that not all stainless steel is made equal. There are numerous grades of stainless steel and some are more noble (the higher the quality) than others. So with all of these different grades of stainless steel, how do you know if yours is more noble? Well, there is a test. All you have to do is take a strong magnet and hold it to the stainless steel. If the magnet is attracted to the stainless (strong pull toward the stainless, sticks right to it and holds on tight) then your stainless steel is less noble. If the magnet is somewhat attracted to the stainless (weak pull, may stick to the stainless, but is easily pulled off) then your stainless is more noble.
On a boat, we want the highest quality of stainless steel we can get. So it's time to get out the magnets and test every screw, bolt, nut, and every other piece of metal on the boat. It's sort of fun, as long as a majority of them are high quality stainless steel ;).