Engineering and Technology Journal

The coupling effect of coating and inhibition has been investigated in the present work. polypyrrole coating with adding coumarin was applied on carbon steel to protect it against corrosion. Electropolymerization process by cyclic voltammeter was carried out in 0.2M oxalic acid electrolyte containing 0.1M pyrrole monomer without and with 0.01M coumarin as an eco-friendly inhibitor. SEM/EDS, AFM and FTIR techniques were used to identify the coating film. Corrosion test using Potentiostat was achieved for uncoated and coated specimens and the results indicated that the corrosion potentials became nobler compared with uncoated specimen, this means that the anodic sites were covered by undoped and doped PPy film as illustrated from the deceasing of anodic and cathodic Tafel slopes. Protection efficiencies were acceptable and good (71.46% for PPy film and 77.47% for coumarin/PPy film). The polarization resistance was increased from 0.114 Ω.cm2 for uncoated C.S. to 0.176 and 0.404 Ω.cm2 for PPy coated and coumarin/PPy coated C.S. While the porosity percentage was 0.44% and 4.50 for PPy coated and coumarin/PPy coated C.S. due to increasing the roughness of coumarin/PPy film.

This research involves study corrosion of low carbon steel under static and flow
conditions at 200L/h in the absence and presence of CO2 at two rates 9 and 30 ml/min
at four temperatures by electrochemical method using potentiostat. Numerical model
was achieved to compare between the experimental and theoretical results to estimate
corrosion rate. The results show that the presence of CO2 under static conditions
shifts the Ecorr toward noble direction, while under flow condition the presence of CO2
shift Ecorr toward active or noble direction at two rates of gas. The data of corrosion
rate in mm/y indicate that the presence of CO2 with two flow rate increased the rate
compared with the case of absence of CO2 under static conditions except one case,
while under flow conditions, the presence of 9 ml/min. CO2 increases the corrosion
rate, while the presence of 30 ml/min. CO2 decreases the rate because of formation
FeCO3 scale except at 298K. A Mathematical model was done which show the
volumetric flow rate of CO2 and finally the corrosion rate of CO2 correlated with
dimensionless groups and independent parameters.