No abstract

No abstract

No abstract

The effect of addition of chloride ion on the corrosion of stainless steel 304 in Na 2 SO 4 solution under constant ionic strength conditions at 30• C was studied using potential-time and potentiodynamic polarization techniques and it was found that the addition of chloride ion reduces the growth of protective passive film on the surface and increase corrosion current. The kinetics of dissolution in sodium chloride solution (0.05-0.5M) at 30• C was also studied and the kinetic rate equation was derived and was found to verify the following relationship: V = k obs C Cl − where k obs = k(K 1 K 2 C H2O /(C H + +K 1 C H + C 2 H2O )) Fe.

Effect of lupine and damsissa extracts on the corrosion of steel in 0.5 M Na2SO4 solution free from and containing 0.01 or 0.1 M NaCl were examined by potentiodynamic and electrochemical impedance spectroscopy techniques. Potentiodynamic polarization curves measurements indicated that damsissa and lupine extracts behave as anodic type inhibitors. Nyquist impedance plots showed type of distorted semicircle whose size increases with increasing concentrations of lupine or damsissa extract. Increasing chloride ion concentration in the solution led to increase of the inhibition efficiency of the extract and this behaviour was explained on the basis of co‐operative mechanism of adsorption. Kinetic–thermodynamic model was used to clarify the nature of adsorption and showed good fit to the experimental data. The results indicated that lupine extract is more effective as corrosion inhibitor for steel in neutral media containing chloride ions than damsissa extract.