Inhibition studies of Rosmarinus officinalis on the pitting corrosion resistance 439LL ferritic stainless steel in dilute sulphuric acid

Abstract

The electrochemical effect of NaCl concentrations (1-5 wt.%) on the corrosion, pitting potential and passivation characteristics of type 439LL ferritic stainless steels was studied in 1 M and 3 M H2SO4 solutions under the inhibiting action of Rosmarinus officinalis through potentiodynamic polarization resistance technique and IR spectroscopy. Results showed that the pitting potential decreased with significant increase in corrosion rates as the concentration of NaCl increased in the absence of Rosmarinus officinalis. Increase in pitting potential, passivation characteristics with significant decrease in corrosion rate was observed with increase in Rosmarinus officinalis concentrations. The average inhibition efficiency of 85 % was obtained. IR spectroscopy showed the presence of alkenes, amines, carboxylic acids, aromatics, alkanes, alkynes and alkyl halides functional groups responsible for the formation of stable complex with the iron constituents. The results obtained establish the dynamic relationship between Rosmarinus officinalis concentrations and the corrosion behavior of the ferritic stainless steel.