Example of cavitation attack in 440C martemsitic stainless steel with hardness about 50HRc. Application was a piston in a hydropower rock drill, life not known. Image aquired on ISI SX-30 microscope, scale bar is 10 microns.
Pitting in Aluminum -
The localized pitting corrosionwas produced in aluminum floats on a storage tank roof. The exposure conditions involved hydrocarbon fluids following an initial hydrotest. The pitting occurred in the absence of chlorides at a near neutral pH where aluminum would be expected to exhibit good resistance to corrosion. Sulfur corrosion products were found in the pits and sulfate reducing bacteria were suspected resulting from prolonged exposure to hydrotest water.
CO2 Pitting Corrosion
Localized pitting corrosion of steel tubing was observed to occur in a CO2 - oil- water mixture. In this particular case, the flow velocity was very low and the mixture was allowed to separate. Oxygen contamination promoted the localized pitting attack and the low flow rate did not produce adequate mixing for the inhibitor to properly disperse in the water phase