Silicon nitride (SiN(x):H) films were deposited onto Al, Mo, Si and Ti substrates by RF plasma-enhanced chemical vapor deposition from mixtures of SiH4 and NH3 with and without hydrogen dilution. Under conditions yielding the same Si/N ratio in the films (0.76); the addition of H-2 to the gas mix increased total bonded H in the film, resulted in a shift from predominantly Si-H to N-H bonding, and yielded higher density films. The anodic polarization behavior of coated and uncoated substrates were characterized in aqueous solutions of HCl and NaCl. Films deposited under conditions of hydrogen dilution exhibited up to three orders of magnitude lower dissolution rates than those deposited in the absence of hydrogen, affording greater protection to the underlying substrates. A high defect density in the SiN(x):H films on aluminum believed to be due to chemical interaction with the substrate during growth, resulted in high anodic current densities due to rapid dissolution of the underlying metal at the defect sites. The scratch resistance of the nitride films on aluminum was lower than on other substrates, apparently due to the softness of the pure aluminum.