Individual and combined effects of fluid flow and inhibitor concentration on inhibition of St-37 steel corrosion using K3PO4 in neutral solution
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Most of the common inhibitors that are used commercially to control the corrosion of steel in neutral solutions are not environmentally friendly. Therefore, use of inhibitors with low toxicities is preferred in industries. The phosphates are inorganic inhibitors with relatively low toxicity that are used in different applications. The solution hydrodynamics is also one of major factors that influence the corrosion behavior of metals and the performance of inhibitors in corrosive systems. Present work is a systematic investigation of the combined effects of inhibitor concentration and hydrodynamic conditions on the electrochemical corrosion behavior of St37 steel in 3.5% NaCl solution containing potassium phosphate. The obtained results showed that behavior of phosphate under hydrodynamic conditions is influenced significantly by its concentration. When the phosphate concentration was relatively high (5 mM), the inhibition efficiencies were not changed by variation of electrode rotation speed. It was attributed to the little influence of hydrodynamic conditions on stability of the protective layers formed on metal surface. It was also observed that at lower phosphate concentrations (less than 1 mM), the inhibitor performance decreased significantly applying hydrodynamic conditions due to the formation of frail and weak protective films on metal surface.
KeywordsInhibition Efficiency Corrosion Current Density Hydrodynamic Condition Rotate Disc Electrode Steel Corrosion
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