Impingement attack is a form of erosion-corrosion caused by the repeated impact of fluids or suspended material hitting a metal surface at high rates, causing removal of material over time. Impingement attack is marked by the delivery of high mechanical wear and chemical corrosion and is especially pronounced when the fluid environment is turbulent.

Key Features:

• Caused by High-Velocity Fluid Flow: Impingement attack occurs in systems with channels for rapid changes to a fluid's direction, such as elbow bends, nozzles, and pump impellers, where high velocities of the fluid and turbulence are both common.
• Localized Damage: Again, the attack will lead to pitting, gouging, or scalloping damage, all of which arise from the constant bombardment of the fluid impact.
• Worsened by Corrosive Media: Fluids that erode or corrode, such as the presence of acids, chlorides, or abrasive suspended material, will increase the attack rate.

Impingement attack is generally occur in equipment such as piping systems, heat exchangers, offshore/marine equipment, and hydraulic turbines that all expose the metal surface to high-speed and turbulent fluid and corrosive environments, all of which results in costly equipment failures that result in leaks and equipment downtime. Prevention strategies to mitigate the effects of impingement attack can include proper material selection (stainless steel or titanium), redesign of flow patterns to reduce turbulence, application of coatings to protect the surface, and velocity control.