(614f) Flowing Fluid Accelerated Degradation of Metal-Protective Coatings

Flow induced corrosion by solid particle impact, liquid impact or bubbles occurs in a wide variety of industrial and everyday life environments, such as pipes, heat exchanger, chemical reactors, liquid-solid heterogeneous catalytic reactors, and so on. Flowing fluid may cause the abrasion of the coatings, enhance the supply of oxygen and diffusion or transport of ions, as a result of influencing corrosion. Studies have been focused on the effects of flow rate on the corrosion of bare metals, with little attention on the degradation of metal-protective coatings.

In order to understand the behavior of flow accelerated organic coating degradation, 3.5 wt% sodium chloride solution and deionized water were chosen as the working fluid. The organic coatings were exposed to laminar channel flow with different flow rates comparing with stationary immersion. The impedance modulus of the organic coating which demonstrates corrosion rate was monitored inline by electrochemical impedance spectroscopy (EIS) under different working fluids and flow rates. The thickness and roughness of the organic coatings were measured before and after the accelerated process. Moreover, equivalent circuit models were established and employed to interpret EIS data so as to analyze the flow effect on individual model elements.