(488ad) Flow-Induced Degradation of Corrosion Protective Coatings: A New Acceleration Factor for Testing

Corrosion protective coatings act as barriers preventing moisture, oxygen, electrolytes, etc to reach the metal structure underneath the coatings. The abilities to accelerate the coating degradation process without altering the mechanism and to predict the service lifetime of decades within a short period of time are essential. Fluid flow over metals has long been believed to influence the corrosion process. However, the influence of fluid flow on the degradation of metal-protective coatings has received less attention. In this preliminary study, we examine the influence of laminar flow on corrosion protective coatings via Electrochemical Impedance Spectroscopy (EIS). A Hele-Shaw cell and its associated fluid control apparatuses are incorporated into the electrochemical cell setup. The barrier properties of the coating as a function of immersion time and flow rate have been monitored by EIS.

We observe that the increase in the flow rate of the electrolyte solution over the coating surface substantially reduces the barrier protection properties of organic coatings on metal substrate, as reflected in the decrease of the electrochemical impedance of the coating. We propose that the flowing electrolyte solution could be used in acceleration tests for the life-time prediction of organic coatings as the acceleration of failure we have observed does not appear to change the mechanism of failure. Modeling and analysis will be performed to understand the electrochemical response of the coatings to the accelerated mass transfer and/or the fluid shear, and to validate immersion flow rate as a universal accelerating parameter for coating failure.