Carbon Steel A36 Planar Coupons Exposed to a Turbulent Flow Inside a 90° Pipe Elbow in a Testing Rack: Hydrodynamic Simulation and Corrosion Studies

This work aims to characterize flow-accelerated corrosion of carbon steel A36 coupons exposed to simulated treated reverse-osmosis seawater under ambient conditions and a Reynolds number range of 6000 to 25,000 using a standard corrosion testing method. The flow behavior in the corrosion compartment and the turbulent parameters were determined by computational fluid dynamics simulation. Using selected flow parameters, complemented with experimental corrosion rate measurements, the oxygen mass transfer coefficients (mc) and the rate constant for the cathodic reaction (kc) at the coupon surface were determined. As expected, mc depends only on the fluid conditions, while kc is highly influenced by interface resistance, leading to significantly different runs with and without a corrosion inhibitor. The dissimilar fluid flow distribution on intrados and extrados generates irregular corrosion patterns, depending on the angular position of the coupon inside the corrosion compartment. Morphological studies using scanning electron microscopy and atomic force microscopy support simulation results.