Chem Question

Your molar mass is the sum of mass contributions from boron and hydrogen; i.e., xB + yH = 27.6335 where B is the atomic mass of boron and H is the atomic mass of hydrogen.
The atomic mass of boron = 10.8 Therefore, the calculated molar mass can incorporate two boron atoms, which together account for 2 * 10.8 = 21.6 g/mol of the molar mass. The remainder (27.6335 - 21.6) must come from hydrogen. Since hydrogen has an atomic mass of 1, 27.6 - 21.6 = 6 => there are 6 hydrogen atoms in the molecule. The molecular formula is therefore B2H6.

I have a question about corrosion. I just did a science lab to determine if salt water would make a piece of steel rust faster than plain water. I put 7.5mL of salt, 15mL and no salt and observed them for 6 days. It turned out that all the pieces rusted at the same rate but the rust on the no salt was bright orange while the rust on the slat water pieces was a dull brown. I would have expected the salt to make it rust faster but that is not what I observed.

Q: Why is the rust on the salt water pieces brown while the rust on the just salt is bright orange?

Q: Why did the salt not make it rust faster?