Dear David, A number of 304 S.S. brackets and plates that handles waste water (treated with Ferric Chloride to coagulate solids) is experiencing corrosion above the waterline. The corrosion appears to be a fine rust and has formed heavily on the inside faces of the stainless plates, the outside faces are completely clean. The water and air have equal exposure to both sides which leads me to believe that the surfaces are somehow different. To my knowledge, no surface treatment was performed on any portion of the plates. All the plates are corroded on the inside (above the water), but not the outside and not below the water line. All the parts in contact are 304 stainless so I don't see how this is galvanic in nature. Any idea what may be causing the corrosion? Thanks,Chris

David, The corrosion is occuring on the inside wall areas of a U-shaped trough (above water line). The trough is open at the top. The ferric chloride concentration of the water should be about the same on both sides of the trough. The outside is not rusting at all. The only difference is there is more flow of the water on the inside of the trough where the water on the outside is basically still. Thanks, Chris