Her worst attacker, other than 108 years in a saltwater environment, is a microorganism that eats iron and craps rust. The "rusticles" (called so by Dr. Ballard, who found her) are basically amoeba poop from these critters.
Brass and other nonferrous inorganics are actually in pretty good shape, where they weren't smashed by the ship hitting the bottom. I wouldn't mind a crack at some of the electric light fixtures still hanging around in there.
Thanks! The Titanic has decayed visibly since its rediscovery due to the digestion. The non-iron components in the iron (impurities introduced for metallurgical reasons) turned out to be the enabling factor for the digestion. In perhaps 50 years it'll just be a decaying pile of junk on the seafloor.