Which form of corrosion is the combined action of chemical attack and mechanical wear due to fluid motion?

• A. Uniform attack
• B. Erosion-corrosion
• C. Intergranular
• D. Galvanic corrosion

Answer: (B)

Erosion-corrosion is the form where chemical attack and the mechanical wear from moving fluid work together to remove material. The chemical part dissolves metal, while the flowing fluid physically abrasively removes protective films and corrosion products. This removal exposes fresh metal to the corrosive environment, so the dissolution process continues more rapidly than it would by chemistry alone. In contrast, uniform attack is just chemical corrosion across the surface without significant mechanical removal; intergranular corrosion occurs along grain boundaries in sensitized materials; galvanic corrosion arises from electrochemical differences between dissimilar metals. The combination of chemical attack plus shear/abrasion from flow makes erosion-corrosion the correct description.