Efficiency of film-forming corrosion inhibitors in strong hydrochloric acid under laminar and turbulent flow conditions

• The effect of flow and inhibitor dosage on corrosion in hot HCl was studied.
• Surface coverage by the inhibitor is key factor controlling corrosion rate under flow conditions.
• At low surface coverage, turbulence benefits mass transport and reduces rate.
• At high surface coverage, turbulence erodes the inhibitor film and increases rate.

The effect of fluid velocity on the corrosion rate of low carbon steel in inhibited 4 M HCl at 80 °C has been examined. When the inhibitor film fully covers the metal surface, the corrosion rate slightly increases with increasing flow velocity which can be attributed to a partial erosion of the inhibitor film. When the inhibitor film coverage is in the lower range, the corrosion takes place at the diffusion limit and an increase in flow velocity results in a strong decrease in corrosion rate due to an increased rate of mass transport of the corrosion inhibitor to the metal surface.

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