ABSTRACT:The corrosion inhibition of aluminum in H 2 SO 4 in the presence of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) and the effect of addition of halides (KCl, KBr, KI) was studied using the hydrogen evolution technique at 30 and 40°C. Inhibition efficiency (%I) increases with concentration of PVA and PEG--but with PEG having higher %I. The %I decrease with increase in temperature from 30 to 40°C in the absence and presence of inhibitor and halides. PVA and PEG were found to obey Freundlish adsorption isotherm. Phenomenon of physical adsorption is proposed from the obtained E a , ⌬G ads , and Q ads values obtained. The synergism parameters (S I ) obtained were found to be greater than unity for both PVA and PEG, which indicates that the enhanced inhibition efficiency caused by the addition of halides is only due to synergism.

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The corrosion and inhibition behavior of carbon steel in hydrogen tetraoxosulphate (IV) acid rich area in the presence of crude saponins and alkaloids extracts of Agrimonia eupatoria leaves have been studied using mass loss and potentiodynamic polarization techniques. The extracts presented good inhibition ability on the carbon steel metal in hydrogen tetraoxosulphate (IV) acid environment with the alkaloids inhibiting more compared to saponins with maximum inhibition efficiency of 97.6 % and 87.8 % respectively at 7.5 g/L concentration. There was a noticeable increase in inhibition mitigation potential of the inhibitors with increasing concentration of extracts. A physical adsorption mechanism was recorded by the inhibitor/carbon steel interface and the Langmuir adsorption isotherm was well obeyed with correlation coefficient at approximately unity. The inhibitors proved to be stable ones on the metal and a spontaneous reaction process was recorded from the data of the Gibbs free energy of adsorption.

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