Keywords : Anodic inhibitors
Engineering and Technology Journal,
2017, Volume 35, Issue 9, Pages 878-886
It is known that corrosion inhibitors and coatings are the best choices to use in oil refinery; therefore, we suggested using both inhibitors and coating to get more efficiency for corrosion control. Polypyrrole coating (PPy) without and with doping by anodic inhibitors were investigated to protect the tank from corrosion in light naphtha unit at Al-Dura refinery. Polypyrrole coating was deposited as nanofibers by electropolymerization using cyclic voltammetry method. Doped polypyrrole coating was applied by adding anodic inhibitor represented by chromate, phosphate and molybdate in acidic electrolyte. The coated layers were examined by SEM/EDS, FTIR and AFM. These examinations showed that coating layers were as nanofibers on carbon steel surface with average roughness in nanoscale as follow: 24.2 nm for PO4≡/PPy, 108 nm for PPy, 122 nm for B4O7=/PPy and 139 nm for MoO4=/PPy coating. Corrosion measurements were investigated by Potentiostat in oil medium at 60oC which represent the average temperature of light naphtha unit; the results showed that the highest protection efficiency was 78.34% in the presence of PO4≡/PPy coating and the others were 77.85% for PPy, 72.64% for B4O7=/PPy and 68.83% for MoO4=/PPy coating. The presence of inhibitor within the structure of polypyrrole coating leads to repairing the defects that may be produced by corrosion process and then the protection will take a long time to be destroyed. The protection by inhibitor doped PPy suggesting reduce the ionic conductivity of coating film especially in the presence of phosphate anions, where the porosity percents was 0.00025 for PO4≡/PPy compared with other coatings (0.04794 for PPy, 0.00043 for B4O7=/PPy, and 0.13083 for MoO4=/PPy).