Wear and Corrosion Due to Impacts

Erosion corrosion is the combined action of erosive wear by impacting solids or liquids and of corrosion. In practice, the term erosion corrosion is often used broadly 

Certain metals corrode at an abnormally high rate when the flow velocity in the turbulent flow regime exceeds a critical value. The phenomenon is well known for copper and its alloys used in domestic hot water systems and in heat exchanger tubes. Table 10.26 indicates empirical values for the critical flow velocity of seawater in condenser pipes made of different alloys. Similar values apply for fresh water. 

The occurrence of a critical flow velocity can be explained in two ways by the action of shear stress on corrosion product films covering the pipe walls or by mass transport considerations. We first consider the role of shear stress. 

The flow of a fluid causes a shear stress Tp at the wall  

/t represents the viscosity, the flow velocity parallel to the wall, and y is the direction normal to the wall. For a Newtonian fluid (constant viscosity) the shear 

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