I think it's very likely that the jackets around the MBP's FireWire, USB, and mini-display ports are made of steel, and I doubt very much that it's stainless steel. There are many other steel parts inside the case, including all the screws, which are certainly not stainless though they may be chrome-plated, and the hard drive and optical drive cases. And there are other metals used in the MBP which are variously subject to corrosion.
Steaming jungles and gritty deserts are implacably hostile environments for all computers (not just portable computers), and it should be taken for granted by everyone who uses computers in such places that the useful life of such equipment will be shortened, perhaps drastically, by doing so. The need to use outside air for cooling makes it impossible to isolate even the machines' innermost recesses from the huge variety of harmful atmospheric and environmental conditions that are encountered on Earth.
In Canada's drier climate the rusting should advance much more slowly, if at all.