Combined attack in which fluid velocity, turbulence or entrained solids keep removing the protective oxide or scale and expose fresh metal to corrosion. It leaves smooth, horseshoe-shaped grooves and wavy patterns aligned with flow, typically at elbows, tees, pump impellers, downstream of control valves and at heat exchanger tube inlets. Flow-accelerated corrosion of carbon steel feedwater and wet steam lines is a closely related, dangerous variant.
Elbow downstream of the choke has erosion-corrosion on the outside radius, wall's down to 40 percent.
Check the outside radius of elbows and the first few diameters downstream of chokes, reducers and control valves before anywhere else.
Also heard as
- impingement attack
- erosion corrosion
Related terms
Uniform corrosion
Corrosion spread evenly over a whole surface, thinning the metal at a fairly predictable rate.
Corrosion allowance
Extra wall thickness added beyond what pressure design needs, meant to be used up by corrosion over the service life.
Cut-out
Section of pipe removed from service so corrosion damage can be examined, tested or replaced.