L-Dopa as Corrosion Inhibitor for Mild Steel in Mineral Acid Medium
Corrosion inhibition of mild steel was studied using L-Dopa in aqueous hydrochloric acid and sulphuric acid so- lutions. The corrosion behaviours of the steel specimen in the presence of inhibitor weret studied by galvanostatic polari- zation and weight loss techniques. The measured electrochemical data indicated good inhibition of corrosion in both the corrosive medium in presence of L-DOPA. The corrosion inhibition may be explained on the basis of adsorption and for- mation of surface film of L-DOPA on the metal surface. The surface of the steel specimen subjected to electrochemical corrosion in the presence and absence of the inhibitor was studied using scanning electron microscopic images. In the present investigation, L-DOPA is used as corrosion inhibitor for mild steel in aqueous hydrochloric acid and sulphuric acid solutions. The corrosion inhibition efficiency of the compound is studied by potentiodynamic polarization and weight loss studies. The surface morphology of the metal surface before and after corrosion is studied by SEM images. 2. EXPERIMENTAL Analytical Reagent (AR) grade chemicals (sd. fine chemicals, Mumbai) were used for the study. The aqueous solution of sulphuric acid and hydrochloric acid was used as the corrosive media. L-dopa was used as received and the structure of the L-dopa was used as corrosion inhibitor is as shown in Fig. (1).
The effect of neutral red on the corrosion inhibition of cold rolled steel in 1.0 M hydrochloric acid
The corrosion inhibition of neutral red on the corrosion of cold rolled steel in 1.0 M hydrochloric acid (HCl) was studied using weight loss method and potentiodynamic polarization method. Results obtained revealed that neutral red is an effective inhibitor. It was found that the adsorption of neutral red could prevent steel from weight loss and the adsorption accorded with the Langmuir adsorption isotherm. Potentiodynamic polarization studies showed that neutral red mainly acted as a mixed-type inhibitor for steel in 1.0 M hydrochloric acid. Thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy were obtained from experimental data of the temperature studies of the inhibition process at four temperatures ranging from 30 to 45 °C. The most suitable range of inhibitor concentration was discussed. The kinetic data such as apparent activation energies and pre-exponential factors at different concentrations of the inhibitor were calculated, the effect of the apparent activation energies and pre-exponential factors on the corrosion rates of cold rolled steel was discussed. The inhibitive action was satisfactorily explained by using both thermodynamic and kinetic models. Synergism between chloride ion and neutral red was proposed. The results obtained from weight loss and potentiodynamic polarization were in good agreement.
Reid on Hypotheses and the Ether; A Reassessment
In recent years historians of science have come to see that Thomas Reid’s Essays on the Intellectual Powers of Man had a profound impact on the development of British methodological thought in the late-eighteenth and early-nineteenth centuries. Larry Laudan has argued that Reid was “the first major British philosopher to take Newton’s opinions on induction, causality, and hypotheses seriously”; and that Reid was thereby instrumental in changing the character of British methodological discourse in the Enlightenment.(1) Geoffrey Cantor has examined in detail the influence of Reid’s critique of ether theories and hypotheses in the Essays on leading protagonists in the nineteenth-century debates surrounding the wave theory of light,(2) and Richard Olson has traced the origins of the scientific style of British physics in the Victorian period to the writings of Reid and other Common Sense philosophers. (3) As well as delineating Reid’s influence, Laudan, Cantor, and Olson have attempted to identify the problems to which he addressed himself in articulating his methodology, and they have analysed with some care the internal structure of his methodological views. Thanks to the work of these historians, therefore, we have a fairly comprehensive picture of Reid’s methodology and its fortunes in the nineteenth century.