Abstract
The effect of immersion time and inhibitor concentration on the corrosion of C-steel in Red Sea Water was studied using chemical and electrochemical techniques. Weight loss data revealed that the corrosion rate expressed as pit depth (mu m year(-1)) is time dependent and obeys the power-law equation P-d = Kt(n). Kinetic parameters indicate that the corrosion of C-steel occurs under mixed control of diffusion and charge transfer processes. The corrosion forms and corrosion products on C-steel were described under different conditions of immersion periods. The addition of Dill seeds aqueous extract (DSAE) reduces the corrosion rate of C-steel in Red Sea Water effectively. It was found that the inhibition efficiency increases with increasing DSAE concentration and the optimal concentration is about 10%. Electrochemical measurements showed that DSAE acts as a mixed-type inhibitor, without altering the mechanism of C-steel dissolution. Inhibition mechanism of DSAE on the C-steel surface was interpreted based on its effective constituents. The effect of DSAE concentration on microbial growth was also studied and discussed in view of its inhibitory action.