Effects of fatigue and corrosion on mild steel yield strength

I'm examining the effects of age and usage on dust collectors for a firm that I'm working for. The current stress analysis that I have performed is all under "ideal" circumstances ie. it doesn't take into account the effects of fatigue from continued usage or potential corrosion. I'm looking for some reliable data sources pertaining to the effects on the yield strength of mild steel (or any steels to be honest) caused by corrosion and fatigue. I know that the yield strength will be lowered as the number of cycles increases and the effects of corrosion will cause weak spots to appear as rust accrues on the body. I'm looking for some reliable online sources of data for this problem but I could use some pointers as to where to find it. Any help would be appreciated :)

Ummm -- would surface finishes prevent corrosion and save wear and tear on your calculator? :)

Fatigue, can't help there as it is very specific to a project and regions where any stresses may be concentrated. Usually best discovered with testing to failure. :)