Investigation of inhibitor effectiveness of organic materials in acidic solutions

In this study, the aim was the prevention of corrosion of boiler steel while it is pickling. Some aminoacids which were D- (-) Mandelic acid, D-Alanine, D-L-Aspartic Acid, D-Phenylalanine, D-Valine, Glycine, Glikolic Acid, L-Methyonine, L-Arginyn, L-Aspargine Monohydrate, L-Cysteinehydrochloridemonohydrate, L-Cystine, L-Histidyne, L-Leucine, N-Acetyle-L-Cysteine, Oxalic Acid were used for corrosion inhibition of boiler steel in wt %0,5 HCl solution and L-Cysteinehydrochloride-monohydrate, L-Cystine, L-Methyonine, N-Acetyle-L-Cysteine were also investigated in wt %0,5 H2SO4 solution. The inhibition efficiencies were calculated with the use of Tafel extrapolation method and Linear polarization method.Various inhibitors were used in %0,5 HCl solution at 35ºC and 1000 ppm. Among them L-Cysteinehydrochloridemonohydrate, N-Acetyle-L-Cysteine, L-Methyonine and L-Cystine were provided high inhibitor efficiency. Inhibitor efficiency was found %87, %83, %84 and %81 respectively. When the experiments were made at 25oC, 45oC and 55oC, it was found that these inhibitors which include sulphur and nitrogen atoms were most effective at high temperatures. After that, the experiments were made at concentrations between 100 ? 3000 ppm at 25oC. High inhibitor efficiency was obtained for L-Cysteinehydro-chloridemonohydrate, L-Methyonine and L-Cystine at 1000ppm, for N-Acetyle-L-Cysteine at 3000 ppm.In wt %0,5 H2SO4 solution, the experiments were made at 1000 ppm and 25oC, 35oC, 45oC, 55oC. For L-Cysteinehydrochloridemonohydrate, L-Methyonine, L-Cystine and Acetyle-L-Cysteine, inhibitor efficiency was found %86, %75, %75 and %81 respectively. Between the 100 ? 3000 ppm at 25oC, inhibitor efficiency increased with increasing concentration. High inhibitor efficiency was obtained at 3000 ppm which are %90, %84, %86 and %75 respectively.The aminoacids affect with adsorption at the metal surface. Adsorption were in accordance with the Langmuir and Freundlich isotherms. Activation energies of the solution were calculated for with and without inhibitor from Lni - 1/T graph at constant inhibitor consantration. The activation energy of the solution without inhibitor were lower than the activation energies of solutions with inhibitor. This result indicates that inhibitor enables protection against corrosion of boiler steel.