Both in static and in dynamic conditions including cavitation erosion and erosion-corrosion, the corrosion rate of Q235 carbon steel in simulating Talimu River (TaR) was much greater than that in Yangtze (YaR) and Yellow River (YeR). Under dynamic conditions, the corrosion rate enhanced a lot, especially in TaR. It was confirmmed that the corrosion section played an important role in the synergistic effect under cavitation and erosion-corrosion conditions. The materials used in the aggressive rivers such as Talimu River under dynamic conditions must resist the synergistic effects between erosion and corrosion.
It was found that the critical flow velocity for 3C carbon steel and 10CrMoAl low alloy steel is 3m/s and 4m/s, respectively, in 2.4% NaCl solution without sea mud. The weight loss rate of test materials decreased with the increasing sea mud content under erosion-corrosion condition in laboratory by using rotating disk rig. Corrosion plays a dominant role for material removal in sea mud containing solution under the erosion-corrosion condition . It should be very careful if the rotating disk rig is suit to do the erosion-corrosion experiment with very fine sea mud (6.6m).
The results showed that in the simulate Zhoushan seawater, the cumulative mass losses and mass loss rates of the ZQAl9-4-4-2 nickel-aluminum bronze and ZQMn12-8-3-2 manganese-aluminum bronze were much less than those for ZHMn55-3-1 manganese brass after cavitaton for 6h. The corrosion current density under cavitation condition was larger about one magnitude than that under quiescent condition for the two materials respectively.
Under the cavitation condition, the cracks propagation of ZQMn12-8-3-2 manganese-aluminum bronze is easy to be parallel to the surface and hindered in the vertical direction to the cavitation surface. The eroded surface damages of ZHMn55-3-1 manganese brass were more seriously than ZQMn12-8-3-2 manganese-aluminum bronze and completely presented the typically spongy cavitation appearance after cavitation for 6h.
The corrosion rate for ZQAl9-4-4-2 nickel-aluminum bronze was increase with 8 times under cavitation condition compared to that under quiescent condition. In the synthetic effect under cavitation condition, the pure erosion (WE) section plays a key role --57.3% . The fragment was equably removed from the eroded surface and it was not found the obviously deep and large cater or cavities. The matrix of ZQAl9-4-4-2 nickel-aluminum bronze was strength by the second phases, boundaries and the twin grids under cavitation condition.
Keywords: Cavitation, Erosion-Corrosion, river, sea water, sea mud, electrochemical test, Flow-handling, TEM
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