I am looking for data relating to corrosion rates for mild steel and stainless steel when used in direct contact with animal wastes blended with high quantities of wheat straw.
The materials will be in the form of 3" dia sch 40 pipe. The blend will be at temps of 70 to 80 C continuously (a highly aerated composting process) Any data re. the life expectancies for exposed piping in this environment would be greatly appreciated.

You may want to check out National Association of Corrosion Engineers (NACE) website... hope that helps ...

I agree with referral to NACE, but would advise to look with bit of skepticism at 316 stainless steel. We have had poor luck in the aquaculture (fish rearing) industry with 316 SS, resulting in a much wider use of titanium to prevent failure due to corrosion. If have to use stainless steel - see if the manufacture can provide 329 stainless steel. The US Navy requires such for all there submersible pumps for base wastewater systems. Pumpex is the only compnay they use due to their use of 329 stainless steel.
Good luck -

Dave Orlebeke
Aquatic Technologies

To determine the corrosive resistance of animal wates you have to break it down into is parts and check an chemical resistance chart for the specific parts. If you pump this, the viscosity increase, increases the wear on the pipe and this is were you may get most of your wear

I haven't determined a corrosion rate, but I do know that either mild steel or 316 SS in direct contact with a high-temp, high-rate composting process will have rapid corrosion levels.  I've seen a 1/4" - 316 SS - temperature probe become porous with numerous cavities through the probe wall (ie. ~1/16" wall) within 4 weeks of direct exposure.  Mild steel will deteriorate even quicker if not adequately coated.  On the other hand, a properly-applied polyurethane coating on mild steel has offered good protection under the same conditions.