1154 Flow Induced Erosion Corrosion

The flow of a gas or electrolyte across the surface of a metal generally enhances the rate of corrosion due to an increase in the rate of mass transport of gaseous and ionic species to the surface and solid products away from the surface. The accelerated corrosion will be uniform if the flow does not produce an uneven diffusion layer at the metal-environment interface. However, localized corrosion may take place because of turbulent flow, that is, flow-induced erosion-corrosion may result (Fig. 11.8). Erosion-corrosion is characterized by the appearance of grooves, gullies, waves, and rounded holes often having a distinct directional pattern. Cavitation corrosion falls within this group and proceeds through the collapse of a vapor bubble. Material loss may arise through mechanical and/or electrochemical mechanisms.

Protruding

Protruding

lent flow.

Bolt

Bolt

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