Abstract
Generally, corrosion rate for steel and cast iron in seawater increases with an increase of the flow rate. On the contrary, in cases where there is a flow rate distribution inside of the pump casing for example, the low flow rate area is sometimes prefferentialy corrodes owing to differential aeration cell caused by a differential flow rate. This study examined the mechanism of the differential aeration cell corrosion owing to the differential flow rate for cast iron in seawater through experiments and numerical analysis. The measurements have been performed on the potential, polarization curves and weight loss for the short-circuited and insulated specimens, and exposed to two different flow rates (0.5m/s and 5.0m/s) of seawater at 25°C also on the galvanic curren betweent short-circuited specimens. A three dimensional boundary element analysis of the potential and galvanic current density distribution for the differential aeration cell in the experiment was also performed. The computational and experimental results matched well. These studies demonstrated that the differential aeration cell corrosion owing to differential flow rate in seawater can be treated in an analogy as galvanic corrosion.
